Nearshore Fish Community Structure in the Southwest Bay

NEARSHORE FISH COMMUNITY STRUCTURE IN THE SOUTHWEST BAY

OF FUNDY AND NORTHWEST ATLANTIC: COMPARING ASSEMBLAGES

ACROSS MULTIPLE SPATIAL AND TEMPORAL SCALES

Collin Arens

B.Sc. (Hon), University of New Brunswick, 2003

A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

Master’s of Science

In the Graduate Academic Unit of Biology

Supervisors: David Methven, Ph.D., Dept of Biology, CRI, UNB Saint John Kelly Munkittrick, Ph.D., Dept of Biology, CRI, UNB Saint John

Examining Board: Matthew Litvak, Ph.D., Dept. of Biology, UNB Saint John Keith Dewar, Ph.D., Faculty of Business, UNB Saint John

This thesis has been accepted by the Dean of Graduate Studies

THE UNIVERSITY OF NEW BRUNSWICK

April, 2007

ABSTRACT

The purpose of this investigation was to assess seasonal, tidal/diel and regional variation in the nearshore fish assemblage of the southwest Bay of Fundy, as well as identify overlying patterns in taxonomic and functional guild structure throughout coastal shallows of the northwest Atlantic. Within the southwest Bay of Fundy species richness and abundance varied seasonally and were correlated with water temperature exhibiting distinct cold and warm water assemblages throughout the year. Over a 24 hour period greater species richness and abundance were observed among samples collected at low tide, with larger fishes captured at night. Regionally, assemblage structure was largely influenced by habitat type with geographic proximity among sites having little direct influence on the structure observed. Throughout the northwest

Atlantic taxonomic structure reflected existing biogeographic provinces with the

Labrador, Acadian and Virginian provinces represented, while functional guild structure exhibited latitudinal gradients with respect to ecological type and egg dispersal.

ACKNOWLEDGEMENTS

There are many people who helped me in many different ways throughout the course of this project and I owe each of them a debt of gratitude. In particular I would like to thank my mother, Kathy Read for her support and encouragement over the years.

I would like to thank my supervisors, Dr. Dave Methven and Dr. Kelly

Munkittrick for their unending patience, guidance and feedback throughout this study, as well as my supervisory committee Dr. Simon Courtenay and Dr. Allen Curry for their suggestions and comments.

I would also like to thank Kevin Shaughnessey, Mark Pokorski, Jason

Casselman, Frederic Vandeperre and Joesph Pratt for their assistance throughout the field sampling; especially during the early mornings and cold winter months when I’m sure there were other places they would have preferred to be.

Finally, thank you to my friends and fellow graduate students; Chris Blanar,

Sandy Brasfield, Jason Casselman, Karen Gormley, Lindsay Jennings, Roshini Kassie,

Mark Pokorski, Kevin Shaughnessey, and my partner Leslie Carroll, who were always willing to lend an ear or put on a pair of waders when I was in need.

Without the assistance of all of these people this project would not have been possible.

TABLE OF CONTENTS

ABSTRACT ...... i

ACKNOWLEDGEMENTS ...... ii

TABLE OF CONTENTS ...... iii

LIST OF TABLES ...... v

LIST OF FIGURES ...... viii

LIST OF SYMBOLS AND ABBREVIATIONS ...... xi

CHAPTER 1: GENERAL INTRODUCTION ...... 12 1.1 Introduction ...... 13 1.2 Literature Cited ...... 16

CHAPTER 2: SPATIAL AND TEMPORAL VARIATION IN THE NEARSHORE FISH ASSEMBLAGE OF THE SOUTHWEST BAY OF FUNDY ...... 19 2.1 Abstract ...... 20 2.2 Introduction ...... 21 2.3 Materials and Methods ...... 24 2.3.1 Study Area ...... 24 2.3.2 Seasonal Sampling (Study 1) ...... 24 2.3.3 Additional Sampling (Studies 2 & 3) ...... 26 2.3.4 Data Analyses ...... 27 2.3.5 Functional Guild Classification ...... 29 2.4 Results ...... 37 2.4.1 Seasonal Variation ...... 37 2.4.2 Functional Guilds ...... 41 2.4.3 Regional Variation ...... 42 2.4.4 Tidal and Diel Variation ...... 44 2.5 Discussion ...... 46 2.5.1 Seasonal Variation ...... 46 2.5.2 Functional Guilds ...... 49 2.5.3 Regional Variation ...... 52 2.5.4 Tidal and Diel Variation ...... 53 2.6 Conclusion ...... 56 2.7 Acknowledgements ...... 57 2.8 Literature Cited ...... 85

iii

CHAPTER 3: LATITUDINAL VARIATION IN TAXANOMIC AND FUNCTIONAL GUILD STRUCTURE OF NEARHSORE FISH ASSEMBLAGES OF THE NORTHWEST ATLANTIC ...... 91 3.1 Abstract ...... 92 3.2 Introduction ...... 93 3.3 Materials and Methods ...... 95 3.3.1 Sources of Data ...... 95 3.3.2 Data Analyses ...... 96 3.3.3 Functional Guild Classification ...... 97 3.4 Results ...... 100 3.4.1 Taxonomic Analyses ...... 101 3.4.2 Functional Guild Analyses ...... 101 3.5 Discussion ...... 104 3.6 Acknowledgements ...... 110 3.7 Literature Cited ...... 133

CHAPTER 4: GENERAL SUMMARY AND CONCLUSIONS ...... 136 4.1 Summary ...... 137 4.1.1 Southwest Bay of Fundy Nearshore Fish Assemblage ...... 137 4.1.2 Northwest Atlantic ...... 139 4.2 Conclusions ...... 140 4.2.1 Functional Guilds ...... 140 4.2.2 Implications for Management of Nearshore Areas ...... 142 4.2.3 Future Research ...... 142 4.3 Literature Cited ...... 144

VITA

LIST OF TABLES

Table 2.1: Name, number, location and dominant substrate type at the 16 sites sampled in this study. Study indicates sites sampled during seasonal (1), regional (2) and tidal/diel (3) studies. See Methods for details...... 58

Table 2.2: Functional guild classification used in this study during the 13 months of sampling at sites 1-3 and 12-14. Abbreviations as follows: Ecological Type - Marine Migrant (MM), Marine Straggler (MS), Estuarine Resident (ER), Estuarine Migrant (EM), Freshwater Migrant (FM), Freshwater Straggler (FS), Diadromous (DA). Vertical Distribution – Pelagic (P), Demersal (D). Reproductive Strategy – Viviporous (V), Ovoviviporous (W), Oviporous (O). Egg dispersal – Pelagic (P), Demersal (D). Residency – Regular (R), Summer Periodic (SP), Winter Periodic (WP), Ocassional (O). Maturity – Juvenile (J), Adult (A), Juvenile and Adult (J/A)...... 59

Table 2.3: Species collected during 13 months of sampling at six sites (1-3, 12-14) in the southern Bay of Fundy, August 2003-2004. The presence of a species at a particular site is indicated by a black dot...... 60

Table 2.4: Correlation coefficients (r) and p values for species richness (S) and abundance (Ni) with average temperature (˚C) and salinity (‰) at the scales of site, region (Passamaquoddy Bay (PB) sites 1-3, Saint John Harbour (SJH) sites 12-14) and the Bay of Fundy (sites 1-3 and 12-14). For each calculation n = 13...... 61

Table 2.5: Functional guild classifications for all species collected during seasonal sampling in the southwestern Bay of Fundy. Abbreviations as follows: Ecological Type - Marine Migrant (MM), Marine Straggler (MS), Estuarine Resident (ER), Estuarine Migrnat (EM), Freshwater Migrant (FM), Freshwater Straggler (FS), Diadromous (DA). Vertical Distribution – Pelagic (P), Demersal (D). Reproductive Strategy – Viviporous (V), Ovoviviporous (W), Oviporous (O). Egg dispersal – Pelagic (P), Demersal (D). Residency – Regular (R), Summer Periodic (SP), Winter Periodic (WP), Ocassional (O). Maturity – Juvinile (J), Adult (A), Juvinile and Adult (J/A)...... 62

Table 2.6: Proportional composition of functional guilds based upon species richness (S) and abundance (Ni) of fishes collected during seasonal sampling in the southwestern Bay of Fundy. Abbreviations as follows: Ecological Type - Marine Migrant (MM), Marine Straggler (MS), Estuarine Resident (ER), Estuarine Migrnat (EM), Freshwater Migrant (FM), Freshwater Straggler (FS), Diadromous (DA). Vertical Distribution – Pelagic (P), Demersal (D). Reproductive Strategy – Viviporous (V), Ovoviviporous (W), Oviporous (O). Egg dispersal – Pelagic (P), Demersal (D). Residency – Regular (R), Summer Periodic (SP), Winter Periodic (WP), Ocassional (O). Maturity – Juvinile (J), Adult (A), Juvinile and Adult (J/A)...... 63

Table 2.7: Estimated size and age of maturity for fishes collected during seasonal sampling in the southwest Bay of Fundy...... 64

Table 2.8: Relative abundance of fishes collected by seine during the regional sampling at 16 sites in the southern Bay of Fundy in October...... 65

Table 2.9: Species collected by seine at each of the 16 sites during the regional sampling in the southern Bay of Fundy, October 16-22, 2004...... 65

Table 2.9: Species collected by seine at each of the 16 sites during the regional sampling in the southern Bay of Fundy, October 16-22, 2004...... 66

Table 2.10: Species collected by seine over two twenty four hour sampling periods at Black Beach, New Brunswick (site 11). Ni indicates the number of individuals collected for each species...... 67

Table 2.11: Summary of diel catch data collected over two twenty four hour periods (September, October) in the southwestern Bay of Fundy at Black Beach. Total species richness (S) and abundance (Ni) are indicated. The number of hauls made during each time period is indicated by n. Black dots indicate species presence...... 68

Table 2.12: Summary of diel catch data collected over two twenty four hour periods (September, October) in the southwestern Bay of Fundy at Black Beach. Variance among hauls for species richness (S) and abundance (Ni) indicated. The number of hauls made during each time period is indicated by n...... 69

Table 2.13: Results of three factor ANOVAs examining influence of sampling period (September 24-25/October 1-2), time of day (TOD, day/night) and tide (low/mid/high), with respect to species richness and abundance. Significant p values (<0.05) are indicated in bold...... 70

Table 2.14: Results Kruskal Wallis non-parametric ANOVAs examining potential influences of tide and time of day on individual fish lengths collected over two twenty four hour periods. Significant p values (<0.05) are indicated in bold...... 71

Table 3.1: Sampling locations and protocols for data used in meta-analysis...... 111

Table 3.2: Species encountered in each of the 15 nearshore areas examined in the Northwest Atlantic. The presence of a species at a particular site is indicated by a black dot...... 112

Table 3.3: Functional guild classification for each species encountered in the 15 nearshore areas examined...... 115

Table 3.3: Functional guild classification for each species encountered in the 15 nearshore areas examined...... 116

Table 3.4: Proportional composition of functional guilds based upon species richness (S) and total catch (Ni) for fishes examined in the NWA. See Methods for explanation of abbreviations...... 119

Table 3.4: Proportional composition of functional guilds based upon species richness (S) and total catch (Ni) for fishes examined in the NWA. See Methods for explanation of abbreviations...... 120

Table 3.5: Statistical results of linear regressions used to examine latitudinal variation of functional guilds with respect to contributions made by species and individuals. n indicates the number of sites available for comparison. Statically significant slopes (p < 0.05) indicated in bold...... 121

vii

LIST OF FIGURES

Figure 2.1: Chart of the southwest Bay of Fundy indicating sample sites used during this investigation. Specific information for each site is listed in Table 2.1...... 72

Figure 2.2: Average monthly temperature (n = 13, dashed line) and salinity (n = 13, dotted line) plotted against species richness and total monthly catch (all species) from combined seasonal collections at six sites (1-3, 12-14) in the southwest Bay of Fundy August 2003-2004...... 73

Figure 2.3: Seasonal patterns of species richness and abundance at site, region and bay scales in the southwest Bay of Fundy...... 74

Figure 2.4: Dendogram of sites 1-3 and 12-14 in the southwest Bay of Fundy as indicated by the Bray-Curtis index of similarity and subsequent break down of group components indicating species present and mean catch per site for each group with n indicating the number of sites within each group...... 75

Figure 2.5: Dendogram of sites 1-3 and 12-14 in the southwestern Bay of Fundy as indicated by the Bray-Curtis index of similarity using a binary data set, and subsequent break down of species composition. Occurrence among groups indicates the percentage of groups in which a species was collected. Within group indicates the percentage of sites within that group each species occurred. n indicates the number of sites within each group...... 76

Figure 2.6: Dendograms identifying seasonal assemblage groupings at the site, region and bay scales in the southwest Bay of Fundy as indicated by the Bray- Curtis index of similarity using binary data. Winter grouping (January to April) is indicated by closed circles...... 77

Figure 2.7: Dendogram of months in the southwestern Bay of Fundy as indicated by the Bray-Curtis index of similarity using a binary data set and subsequent break down of species composition. Occurrence among groups indicates the percentage of groups in which a species was collected. Within group indicates the percentage of sites within that group each species occurred. n indicates the number of sites within each group...... 78

Figure 2.8: Standard length (SL) of individual fish in relation to month of collection. Dotted line indicates the approximate size of first spawning...... 79

Figure 2.9: Species richness, abundance and percent composition of M. menidia from 16 sites sampled in the southwest Bay of Fundy between October 16 and 22, 2004...... 81

viii

Figure 2.10: Dendogram of sites 1-16 in the southwest Bay of Fundy as indicated by the Bray-Curtis index of similarity and subsequent break down of group components indicating species present and mean abundance per site for each group with n indicating the number of sites within each group...... 82

Figure 2.11: Species richness and abundance in relation to tidal amplitude from samples taken over two twenty four hours periods on September 24-25 and October 1-2, 2004. Night hours are indicated by the thatched area...... 83

Figure 2.12: Size distribution of nearshore fishes collected over two 24 hour periods during September and October 2004 using a seine in the southwest Bay of Fundy. Mean length +/- standard error and median indicated...... 84

Figure 3.1: Location of nearshore studies used in large scale comparison. Biogeographic provinces identified by dashed lines and italics...... 122

Figure 3.2: Number of species (closed dots, solid trend line r2: 0.954) and families (open dots, dashed trend line r2: 0.970) encountered in nearshore collections throughout the northwest Atlantic in relation to latitude. Cape Cod also indicated (dotted grey line)...... 123

Figure 3.3: Percent similarity of 15 nearshore areas examined in the northwest Atlantic based on family data as indicated by the Bray-Curtis index using a binary matrix. Zoogeographic provinces listed (Briggs 1974). See Table 3.1 for site details...... 124

Figure 3.4: Percent similarity of 15 nearshore areas examined in the northwest Atlantic based on species data as indicated by the Bray-Curtis index using a binary matrix. Zoogeographic provinces listed (Briggs 1974).See Table 3.1 for site details...... 125

Figure 3.5: Proportion of species and individuals exhibiting specific ecological types across latitude. See text for guild definitions...... 126

Figure 3.6: Proportion of species and individuals exhibiting pelagic (P) or demersal (D) vertical distributions across latitude. See text for guild definitions...... 128

Figure 3.7: Proportion of species and individuals exhibiting viviparous (V), ovoviviparous (W) and oviparous (O) reproductive types across latitude. See text for guild definitions...... 129

Figure 3.8: Proportion of species and individuals exhibiting pelagic (P) or demersal (D) egg dispersals across latitude. See text for guild definitions...... 130

Figure 3.9: Proportion of species and individuals exhibiting regular (R), summer periodic (SP), winter periodic (WP) and occasional (O) residency types across latitude. See text for guild definitions...... 131 ix

Figure 3.10: Proportion of species and individuals exhibiting juvenile (J), adult (A) and mixed (J/A) maturity types across latitude. See text for guild definitions. 132

LIST OF SYMBOLS AND ABBREVIATIONS

°C Degrees Celsius

% Percent

ANOVA Analysis of Variance

ß Beta cm Centimetre

CRI Canadian Rivers Institute df Degrees of Freedom hrs Hours m Meter mm Millimetre n Number

N North

Ni Number of Individuals

NEA Northeast Atlantic

NWA Northwest Atlantic ppt Parts Per Thousand r Correlation Coefficient r2 Regression

S Species Richness

SL Standard Length

W West

1 CHAPTER 1: GENERAL INTRODUCTION

1.1 Introduction

Estuaries and associated coastal waters are recognized as regions of high productivity that support large densities of biomass including both fish and invertebrates

(Haedrich 1983, Elliott 2002). With respect to ichthyofauna these habitats serve as nursery grounds for juveniles, as foraging and spawning sites for adults, and as migratory routes for anadromous and catadromous species (McHugh 1967, Beck et al.

2003). Despite wide acceptance of the significance these habitats have for fishes at various life history stages, several gaps exist in our current understanding of how fish communities are structured in the northwest Atlantic and the processes that influence species composition at different spatial and temporal scales. This information is becoming of greater importance as regulatory bodies look to protect and manage nearshore environments (Agardy 1994, Jamieson and Levings 2001, Beck et al. 2003).

Given that habitat and resource requirements vary among fishes and change throughout ontogeny, species are continuously migrating in and out of the nearshore area to meet specific biological needs. This results in a dynamic community that is constantly changing in terms of its composition and structure. Changes in assemblage structure are accentuated by the changing physical conditions of the estuarine environment, with variation observed in response to factors such as tidal height, photointensity, salinity and temperature (Haedrich 1983). Nearshore fishes compensate for the dynamic nature of estuarine and coastal waters by occupying different habitats throughout their life cycles, maximizing their potential for growth while reducing physiological stress and the risk of mortality (Gibson et al. 1996, Morrison et al. 2002).

Traditionally our understanding of nearshore fish assemblages has largely been focused on the analysis of taxonomic divisions (i.e., the presence, abundance and/or biomass of species). This understanding has been extended over the past decade by analyzing the ecological structure of nearshore ecosystems through the use of functional guilds (e.g., Elliot and DeWailly 1995, Whitfield 1999, Mathieson et al. 2000, Thiel et al. 2003). Functional guilds summarize the ecological structure of a fish assemblage by grouping species according to similarities in specific biological and ecological traits

(Brown 2004) allowing for the creation and testing of models concerning the ecological structure of a ecosystem (e.g., prevailing means of egg dispersal) which may not be possible when examining taxonomic attributes alone. The functional guild approach is independent of taxonomic classification and hence facilitates cross-site comparison over large geographic areas which support distinctive biota and thus could not be readily compared based upon phylogenic relationships alone (Gitay and Noble 1997).

Research on temperate nearshore fish assemblages in the northwest Atlantic

(NWA) has typically focused on seasonal variation among individual estuaries (e.g.,

Hillman 1977, Lazzari 1999, Layman 2000, Methven et al. 2001, Wilbur et al. 2003), with comparatively little attention given to comparisons across large geographic areas or at small temporal scales. However, quantifying variation at these scales is essential in coastal zone management. Without an adequate understanding of the ecological processes operating at these scales, monitoring programs can not account for natural variability, confounding resulting data and limiting its effective use (Elliott 2002).

Throughout temperate regions of the northeast Atlantic (NEA) changes in assemblage structure have been examined across large geographic areas utilizing

15 taxonomic and functional traits (Elliott and DeWailly 1995, Mathieson et al. 2000,

Elliott 2002, Thiel et al. 2003). Comparable research has been lacking throughout the

NWA given that data have previously been insufficient for analysis; particularly throughout the Canadian Atlantic. As a consequence, past research encompassing large geographic areas in the NWA have either focused on southern latitudes (Monteiro-Neto

1990, Vieira and Musick 1994), or have been based on data sets limited in terms of their temporal scope and the suitability of their sampling methods for comparison (Nordlie

2003). Fortunately, considerable data have been collected from nearshore communities of the northeast United States since the late 1990’s (e.g., Lazzari 1999, Able et al. 2002,

Wilbur et al. 2003) as well as portions of the Canadian Atlantic (e.g., Methven et al.

2001, data presented herein). As a consequence it is now possible to examine variation over large geographic areas throughout the NWA.

There were two main objectives to this investigation. The first objective was to assess temporal and spatial variation in the nearshore fish assemblage structure of a previously under-described portion of the Canadian Atlantic; the southwest Bay of

Fundy. This was addressed by examining; a) temporal variability at seasonal and tidal/diel scales; b) spatial variability throughout the region and; c) identifying prevalent ecological characteristics through the use of functional guilds. The second objective was to then use these data in conjunction with existing nearshore records from throughout the

NWA, ranging from Newfoundland, Canada (47° N) south to Virginia, USA (36° N), and conduct a meta-analysis in order to identify patterns in taxonomic and functional guild structure over a large geographic scale.

1.2 Literature Cited

Able, K.W., M.P., Fahay, K.L., Heck, C.T. Roman, M.A. Lazzari, and S.C. Kaiser. 2002. Seasonal distribution and abundance of fishes and decapod crustaceans in a Cape Cod estuary. Northeastern Naturalist. 9: 285-302.

Agardy, M.T. 1994. Advances in marine conservation: The role of marine protected areas. Trends in Ecology & Evolution. 9: 267-270.

Beck, M.W., K.L. Heck, K.W. Able, D.L. Childers, D.B. Eggleston, B.M. Gillanders, B.S. Halpern, C.G. Hays, K. Hoshino, T.J. Minello, R.J. Orth, P.F. Sheridan, and M.P. Weinstein. 2003. The role of nearshore ecosystems as fish and shellfish nurseries. Issues in Ecology. 11: 1-12.

Brown, C.S., 2004. Are Functional Guilds More Realistic Management Units Than Individual Species for Restoration? Weed Technology. 18: 1566–1571.

Elliot, M., and F. DeWailly. 1995. The structure and components of European estuarine fish assemblages. Netherlands Journal of Aquatic Ecology. 29(3-4): 397-417.

Elliott, M., and K.L. Hemingway. 2002. Fishes in Estuaries. Blackwell Science. Oxford, UK. 636 pp.

Gibson, R.N., L. Robb, M.T. Burrows, and A.D. Ansell. 1996. Tidal, diel and longer term changes in the distribution of fishes on a Scottish sandy beach. Marine Ecology Progress Series. 130: 1-17.

Gitay, H., and I.R. Noble. 1997. What are functional types and how should we seek them? In Plant Functional Types: their relevance to ecosystem properties and global change. (Smith, T.M., H.H. Shugart and F.I. Woodward, ed.). Cambridge University Press. New York. 369 pp.

Haedrich, R.L. 1983. Estuarine Fishes. In Estuaries and Enclosed Seas. Ecosystems of the World 26 (Ketchum, B.H., ed.). Elsevier Scientific, New York. pp. 183-207.

Hillman, R.E., N.W. Davis, and J. Wennemer. 1977. Abundance, diversity and stability in shore-zone fish communities in an area of Long Island Sound affected by the thermal discharge of a nuclear power station. Estuaries and Coastal Marine Science. 5: 355-381.

Jamieson, G.S., and C.O. Levings. 2001. Marine protected areas in Canada— implications for both conservation and fisheries management. Canadian Journal of Fisheries and Aquatic Science. 58: 138–156.

Layman, C.A. 2000. Fish assemblage structure of the shallow ocean surf-zone on the eastern shore of Virginia barrier islands. Estuarine, Coastal and Shelf Science. 51: 201-213.

Lazzari, M.A., S. Sherman, C.S. Brown, J. King, B.J. Joule, S.B. Chenoweth, and R.W. Langton. 1999. Seasonal and annual variations in abundance and species composition of two nearshore fish communities in Maine. Estuaries. 22: 636-647.

Mathieson, S., A. Cattrijsse, M.J. Costa, P. Drake, M. Elliott, J. Gardner, and J. Marchand. 2000. Fish assemblages of European tidal marshes: a comparison based on species, families and functional guilds. Marine Ecology Progress Series. 204: 225-242.

McHugh, J.L. 1967. Estuarine nekton. In Estuaries. (Lauff, G.H. ed.). American Association For the Advancement of Science, Washington, DC. 83: 581-620.

Methven, D.A., R.L. Haedrich, and G.A. Rose. 2001. The fish assemblage of a Newfoundland estuary: Diel, monthly and annual variation. Estuarine, Coastal and Shelf Sciences. 52: 669-687.

Monteiro-Neto, C. 1990. Comparative community structure of surf zone fishes in the Chesapeake Bight and Southern Brazil. PhD Thesis, Faculty of the School of Marine Science, The college of William and Mary, Virginia, United States.

Morrison, M.A., M.P. Francis, B.W. Hartill, and D.M. Parkinson. 2002. Diurnal and tidal variation in the abundance of fish fauna of a temperate tidal mudflat. Estuarine, Coastal and Shelf Sciences. 54: 793-807.

Nordlie, F.G. 2003. Fish communities of estuarine salt marshes of eastern North America, and comparison with temperate estuaries of other continents. Reviews in Fish Biology and Fisheries. 13: 281-325.

Thiel, B.R., H. Cabral, and M.J. Costa. 2003. Composition, temporal changes and ecological guild classification of the ichthyofaunas of large European estuaries – a comparison between the Tagus (Portugal) and the Elbe (Germany). Journal of Applied Ichthyology. 19: 330-342.

Vieira, J.P., and J.A. Musick. 1994. Fish fauna in warm-temperate and tropical estuaries of western Atlantic. Atlântica. 16: 31-53.

Whitfield, A.K. 1999. Ichthyofaunal assemblages in estuaries: A South African case study. Reviews in Fish Biology and Fisheries. 9: 151-186.

Wilber, D.H., D.G. Clarke, M.H. Burlas, H. Ruben, and R.J. Will. 2003. Spatial and temporal variability in surf zone fish assemblages on the coast of northern New Jersey. Estuarine, Coastal and Shelf Sciences. 56: 291-304.

2 CHAPTER 2: SPATIAL AND TEMPORAL VARIATION IN THE

NEARSHORE FISH ASSEMBLAGE OF THE SOUTHWEST BAY OF

FUNDY

2.1 Abstract

The purpose of this investigation was to examine how the structure of the nearshore fish assemblage in the southwest Bay of Fundy varied across multiple spatial and temporal scales. Fishes were collected from a depth of approximately 1 meter using a beach seine: 1) seasonally, sampling six sites every two weeks throughout the year; 2) regionally, sampling 16 sites throughout the southwest Bay of Fundy over one week and; 3) tidally, sampling a single site at two hour intervals over two 24 hour periods.

Overall the nearshore fish assemblage consisted of eighteen species and exhibited a high degree of dominance. The majority of species occurring in the assemblage were demersal juveniles of marine origin derived from pelagic eggs occurring periodically in the nearshore area. Species richness and abundance varied seasonally and were correlated with water temperature. Regional variation was influenced by substrate type with similar habitats exhibiting similar assemblages while spatial proximity among sites had little influence on the assemblage. Over a 24 hour period considerable variation in richness and abundance was observed in response to tide and time of day with the greatest diversity observed at low tide while peaks in abundance occurred at twilight.

Overall the nearshore assemblage was influenced by a number of physical and biological factors operating at multiple spatiotemporal scales.

2.2 Introduction

Estuaries and associated coastal waters are regions of high primary productivity that naturally support high densities of biomass (Haedrich 1983, Elliott 2002). These nearshore areas are of particular importance along temperate coasts where fishes and crustaceans use them as nurseries, foraging grounds, and spawning sites, as well as corridors between freshwater and marine ecosystems (McHugh 1967, Beck et al. 2003).

Among estuarine fishes, habitat and resource requirements vary among species and change throughout ontogeny. As a consequence, fishes are continuously migrating in and out of estuaries to meet specific biological needs. This results in a dynamic community that is constantly changing in terms of its composition and structure. These changes in assemblage structure are accentuated by the dynamic physical conditions of nearshore environments, with considerable changes being observed in factors such as tidal height, photointensity, salinity and temperature (Haedrich 1983). Nearshore fishes compensate for the dynamic nature of estuarine and coastal waters by occupying different habitats throughout their life cycles, and maximizing their potential for growth, while reducing physiological stress and the risk of mortality (Gibson et al. 1996). These movements are often continuous and dynamic, operating at different spatial and temporal scales, ranging from daily habitat shifts with the rising tide, to offshore spawning migrations (Pitman and McAlpine 2003).

Fishes do not respond to their environment at a single spatial or temporal scale and multi-species assemblages vary in their response to the environment due to functional differences among those species (Pittman and McAlpine 2003). Studies

22 incorporating multiple levels of spatial and temporal scale have become an important tool in developing a comprehensive understanding of the spatiotemporal variability within an assemblage (Schneider 1994, Pittman and McAlpine 2003). Multi-scale studies have become more frequent over the past 15 years, with considerable research on nearshore marine assemblages occurring in the United States (Ayvazian et al. 1992,

Lazzari et al. 1999, Piatt et al. 1999, Wilber et al. 2003, Able et al. 2002), Australia

(Jackson and Jones 1999), Europe (Gibson et al. 1993, Lobry et al. 2003) and South

Africa (Dye 1998, Whitfield 1999). As a result, a number of common features have been identified among these environments, such as seasonal variability in assemblage composition and an overall dominance by juvenile fishes. However, distinct differences are also prevalent among nearshore communities, as the structure and composition of assemblages vary among zoogeographic provinces (e.g., Ayvazian 1992), and habitat types (Sogard and Able 1991). Distinct differences are also present in the relative importance of these areas for the successful recruitment of commercial finfish (Able et al. 2002). As a consequence not all patterns in community structure are universal and localized patterns in assemblage structure have developed within regions where species have adapted to the meet specific physical conditions. Due to this spatial variability over the large scale it is necessary to conduct multi-scale studies within regions of interest in order to identify localized patterns in spatiotemporal variability specific to that area.

Unfortunately this information is still largely lacking from a number of important areas across the globe, including areas hosting some of the world’s most productive fisheries.

In addition to multi-scale studies, our understanding of estuarine communities has also been improved recently by examining the ecological structure of these

23 environments through functional guild analyses in addition to traditional analyses of taxonomic attributes (i.e., the presence, abundance and/or biomass of different taxa).

The use of functional guilds was first proposed for use in estuarine ecosystems by

McHugh (1967), and has been further developed by Haedrich (1983), Elliot and

DeWailly (1995), and Whitfield (1999). This approach has the advantage of identifying ecological variation among ecosystems (e.g., identifying the dominant means of egg dispersal) which may not be evident when examining taxonomic attributes alone.

Additionally the functional guild approach is independent of taxonomic classification within the fish assemblage. Therefore it allows for comparisons across zoogeographic areas which support unique biota and could not be readily compared otherwise. To date, the functional guild concept has mainly been applied to fish in European estuaries

(Elliott and DeWailly 1995, Mathieson et al. 2000, Thiel et al. 2003), with limited use in

North America.

The objective of this study was to assess spatial and temporal variation within a previously under-described nearshore fish assemblage of the Canadian Atlantic; the southwest Bay of Fundy. This was addressed by examining; a) temporal variability at seasonal (study 1) and tidal/diel scales (study 3); b) spatial variability throughout the region (study 2) and; c) identifying prevalent ecological characteristics through the use of functional guilds.

2.3 Materials and Methods

2.3.1 Study Area

The study area was located in the southwest portion of the Bay of Fundy (c. 45°

00 N, 65° 50 W, Figure 2.1). Tides form the dominant physical variable in the region ranging in amplitude from 6-8 m in the study area to 12 m at the head of the Bay (Trites and Garrett 1983), resulting in strong tidal currents as well as widespread mixing of the water column (Lotze and Milewski 2002). As a consequence of its tidal amplitude the southwest Bay of Fundy has an extensive intertidal zone comprised of 9.7% salt marshes and mudflats, 35.2% bedrock, and 55% of coarse sedimentary shores ranging in composition from broken rock to sand with a low coastal relief (Thomas et al. 1983).

2.3.2 Seasonal Sampling (Study 1)

Sampling was conducted at six sites in the southwest Bay of Fundy. Three sites were located in Passamaquoddy Bay (sites 1-3) with three additional sites located in the vicinity of Saint John Harbour (sites 12-14, Table 2.1, Figure 2.1). Sites were chosen based on year-round accessibility, lack of ice in winter and the presence of substrates conducive to sampling with a small seine (e.g. areas of low coastal relief free of large rocks and debris). Seine collections described below were made at each of the six sites twice per month for thirteen consecutive months from August 2003 to August 2004.

During each collection, two consecutive hauls were made with the seine parallel to the shore. To maintain comparability among samples and sites, the time required during each haul was standardized to three minutes. The mean area covered during each haul

25 was determined to be 224 +/- 4.7 m2 based upon 48 hauls measured between July and

August 2004. All sampling was performed during the day, commencing at low tide, and was completed within three hours, to minimize the influence of tidal and diel variability

(Lasiak 1984, Gibson et al. 1996).

All collections were made using a 9 x 1.5 m beach seine (9 mm stretch mesh) with a central collection bag which sampled the entire water column to a depth of approximately 1 m. Additional details on the seine and its deployment are reported in

Methven and Bajdik (1994). After each site was sampled, surface water temperature and salinity were recorded from a depth of approximately 50 cm using a handheld thermometer and a handheld Westover RHS-10ATC temperature compensated refractometer.

Captured fishes were transferred to a holding tank on site, identified to species, and counted and measured (standard length SL, nearest mm), prior to live release once sampling at each site was completed. Occasionally, specimens requiring further scrutiny or that were collected in extremely high abundance were anesthetised using Tricaine

Methanosulfate (TMS) and fixed in 5% formalin before being transported to the laboratory for identification. Fish identification was based on characteristics given by

Scott and Scott (1988), Able and Fahay (1998) and Colette and Klein-MacPhee (2002).

All preserved specimens were contributed to the New Brunswick Museum ichthyology collection in Saint John.

2.3.3 Additional Sampling (Studies 2 & 3)

Additional sampling was also conducted to characterize small scale temporal and spatial variation in nearshore catches of the southwest Bay of Fundy. Jenkins and

Wheatley (1998) in southern Australia and Sogard and Able (1991) in the northwest

Atlantic identified considerable variation in fish assemblage structure among different habitat types, while Lasiak (1984) and Gibson et al. (1996) identified significant variation in response to tide and time of day. As a consequence, two additional studies were conducted in order to examine the influence of these small scale processes on species richness and abundance in the southwest Bay of Fundy. The first examined spatial variability among various habitat types (study 2), while the other examined tidal and diel variability (study 3). Preliminary findings from the seasonal sampling (study 1) described above indicated the optimal period to conduct the additional sampling was in

September and October, which offered high species richness and total abundance as well as equal hours of daylight and darkness for comparison (12:12). Collections were made using the same sampling equipment and methods described previously unless stated otherwise.

Regional variation (study 2) of the nearshore fish assemblage in the southwest

Bay of Fundy was examined at 16 sites spanning approximately 140 km of coastline

(sites 1-16, Table 2.1, Figure 2.1). Collections were made over a six day period from

October 17-22, 2004 with three seine hauls each two minutes in duration made at each site. All sampling was performed during the day, commencing at low tide and was completed within three hours in order to reduce the influence of tidal and diel variability on the collected data (Lasiak 1984, Gibson et al. 1996).

Tidal (c. 6 hr) and diel (12 hr) variability (Study 3) in fish catch were examined over two twenty four hour periods (September 24-25 and October 1-2, 2004) at Black

Beach (site 11, Table 2.1, Figure 2.1). The beach is approximately 200 m long and bordered by rocky headlands. Due to the 9 m tidal range (Thomas 1983) and low coastal relief typical of the area, the site exhibited an extensive intertidal zone consisting of a uniform sandy substrate persisting throughout the intertidal zone changing to soft sediments, primarily mud, in the subtidal zone. Sampling was conducted during the autumn when hours of daylight equalled hours of darkness (12:12), and sampling periods were separated by one week to allow for the comparison of contrasting tidal cycles (e.g., low tide occurred at 3:00 pm in September while high tide occurred at the same time in October). This approach permitted the separation of tidal and diel effects and is similar to study designs used by Lasiak (1984) in South Africa and Gibson et al.

(1996) in Scotland. Collections were made every two hours over the two 24 hour periods. During each two hour period three hauls of the seine, each of two minutes duration were made for a total of 78 hauls.

2.3.4 Data Analyses

Seasonal data were examined at a monthly scale combining biweekly collections made during the same month. Since comparable sampling effort was used during each collection, non-transformed data were additive and combined into six 18 species (the total number of species collected) by 13 month matrices, one for each site. Although combining the data resulted in a loss of information (i.e., 26 samples collapsed into 13

28 for each site) it was necessary to permit the data to be examined at a monthly resolution allowing for comparison with previous studies of seasonality (e.g. Ayvazian et al. 1992,

Lazzari et al. 1999, Methven et al. 2001).

Variation in abundance and richness were examined at the scales of site, region and bay. The site scale is defined as the data collected from each of the six sites (1-3 and

12-14) examined independently and is based on four seine hauls per month at each site.

The regional scale is defined as data collected from Passamaquoddy Bay (sites 1-3) and vicinity of Saint John Harbour (sites 12-14, Figure 1). Data within regions were combined to produce two 18 species by 13 month matrices based on a total of 12 seine hauls per month at each region. The bay scale (southwest Bay of Fundy) is defined as site data from each of the six sites combined into a single 18 species by 13 month matrix based upon 24 seine hauls per month. Pearson correlation coefficients were determined for species richness and abundance from average monthly temperatures and salinities at the site, region and bay levels of scale. All means were expressed with +/- standard error.

Similarities in species richness and abundance were examined among sites and months using cluster analyses based upon the Bray-Curtis coefficient of similarity (Bray and Curtis 1957). The Bray-Curtis coefficient identifies similarities among samples based on the species richness and abundance within each sample. This information allows samples to be clustered into groups which have similar communities, so that samples within each group share a greater similarity to each other than with samples from other groups. Data were square-root transformed to reduce the influence of highly abundant species on the final result (Field et al. 1982). In addition to this, a binary data

29 set was also analyzed using the Bray-Curtis coefficient to determine similarity among sites and months based upon the presence/absence of each species. This analysis gives dominant and rare species equal weighting (Field et al. 1982). All cluster analyses were conducted using the PRIMER 5 statistical package.

Twenty-four hour variability in assemblage structure was assessed using three factor analyses of variance (ANOVAs) to identify significant differences in species richness as well as abundance in response to sampling period (month: September,

October), time of day (day, night) and tidal height (high tide >6m, mid tide 3-5m and low tide <3m). Post-hoc tests of tidal impacts were also conducted in order to establish which tidal heights were significantly different from each other (low-high, low-mid, mid-high). Species richness data were square root transformed ( X '= (x + 0.5) ) and abundance data log transformed ( X '= log(X +1) in order to meet the assumptions of the ANOVA that data are normally distributed and exhibit homogeneity of variance.

Pearson correlation coefficients were used to examine relationships between species richness and abundance with respect to tidal amplitude. Variation in length was also examined using the Kruskal-Wallis non parametric ANOVA in response to time of day and tide. All univariate analyses were conducted using SYSTAT 11 software.

2.3.5 Functional Guild Classification

In order to examine the ecological structure of the fish assemblage, functional guilds were developed to classify species into discrete groups (guilds) based upon shared biological and ecological characteristics. Each species collected throughout the seasonal

30 sampling was assigned to a single guild within each of the six guild types examined

(Table 2.2). For example, in terms of vertical distribution, species were grouped into pelagic or demersal guilds depending where they commonly occur in the water column.

The proportional contributions made by both the number of species and the number of individuals to each guild were then calculated in order to determined the dominant functional traits of the southwest Bay of Fundy fish assemblage.

Given that functional guilds cover a variety of biological and ecological characteristics, the categorization of some traits differ depending upon the spatiotemporal scale in which they are examined. This has direct implications for how these data can be interpreted and compared (Gitay and Noble 1997). As a consequence, the six guild types examined in this study have been divided into static or fluid groupings depending on whether or not they are scale dependent. The four static guild types (ecological type, vertical distribution, reproductive type and egg dispersal), assign species to guilds based on biological and/or ecological information which is independent of the spatiotemporal scales examined. For example, species producing pelagic eggs do so throughout their range. As a consequence species are assumed to belong to the assigned guild regardless of when or where it is encountered. In situations where a species could potentially occupy multiple guilds due to changes throughout ontogeny, only the adult characteristics are considered. For example, Urophycis tenuis is pelagic during the larval stage; however the demersal adult stage is used in classification. Fluid guilds however (residency, maturity), vary depending on the spatiotemporal scale examined. For example, with respect to the residency guild, a species occurring only during the summer months in a temperate estuary may occur year-round in a warmer

31 environment. As a consequence, species may be assigned to different guilds depending on when and where the data was collected. Although not all of the guilds described below occurred in the southwest Bay of Fundy, (e.g. ovoviviparous species which are uncommon in the Northwest Atlantic, but are present in the Northeast Pacific), they were included to facilitate comparisons with ecosystems where they do. The classification system used in this study was developed based upon previous work with plant and fish communities conducted by Tyler (1971), Elliott and DeWailly (1995),

Gitay and Noble (1997), Whitfield et al. (1999), Mathieson et al. (2000), Methven et al.

(2001) and Thiel et al (2003). Able and Fahay (1998), and Collette and Klein-MacPhee

(2002) describe the general biology of each species collected in this study and were the primary sources of information used to classify species among static guilds.

Ecological Type

Ecological type places species collected in this study into one of seven guilds and is largely based upon the classification system proposed by Whitfield (1999) for South

African fishes. Whitfield’s (1999) guilds have been modified in this study due to the replacement of the catadromous life history strategy with diadromous in order to include anadromous and amphidromous fishes which were not observed in South African waters, but also utilize estuaries largely as a migration corridor.

Each of the following guilds considers two aspects of each species’ ecology: 1) the environment in which it spawns, and 2) the extent to which it utilizes the estuarine environment. Fishes spawn in one of three environments: marine (M), estuarine (E), or freshwater (F) and this is indicated by the first letter in each guild. The extent to which a

32 species utilizes the estuarine environment is indicated by the second letter. Resident species (R) reside in estuaries throughout ontogeny. Migratory species (M) are known to regularly move in and out of estuaries, and stragglers (S) denote adventitious species from freshwater or marine environments that are occasionally taken in estuaries. An additional guild was also created for diadromous species (DA) which largely use the nearshore area as a migration corridor between fresh and saltwater spawning habitats.

Overall a total of seven different life history guilds were identified with regards to ecological type:

• Marine Migrants (MM) spawn in the marine environment and typically make

extensive use of estuaries as a foraging ground or nursery area during the

juvenile stages before migrating offshore (e.g., Urophycis tenuis, white hake).

• Marine Stragglers (MS) spawn and complete their entire life cycles further

offshore but occasionally appear in the estuarine environment (e.g., Limanda

ferruginea, yellowtail flounder).

• Estuarine Residents (ER) spawn within the estuary and reside there throughout

ontogeny (e.g., Menidia menidia, Atlantic silverside).

• Estuarine Migrants (EM) spawn in estuaries but make extensive use of marine or

freshwater habitats during their life cycles (e.g., Gasterosteus wheatlandi,

blackspotted stickleback).

• Freshwater Migrants (FM) spawn in freshwater but frequently migrate into

estuaries when conditions are favourable (e.g., Pungitius pungitius, ninespine

stickleback).

• Freshwater Stragglers (FS) spawn and complete their entire life cycle in

freshwater but occasionally appear in estuaries (e.g., Notropis heterolepis,

blacknose shiner).

• Diadromous (DA) species which regularly migrate between freshwater and

seawater, often residing in one environment while spawning in the other. This

guild includes anadromous (e.g., Osmerus mordax, rainbow smelt), catadromous

(e.g., Anguilla rostra, American eel) and amphidromous fishes (e.g., Eleotris

acanthopoma, sleeper).

Vertical Distribution

Vertical distribution examines the partitioning of vertical space with each species assigned to a guild based upon their degree of association with the substratum. This type was modified from the vertical distribution category proposed by Elliot and DeWailly

(1995) by eliminating the benthic guild since it is often difficult to distinguish between the demersal and benthic life history traits based on information available in the scientific literature. For example, members of the Cottidae and Gadidae families are often in direct contact with the substrate (benthic trait) but also move throughout the water column in close association with the substrate (demersal trait, Colette and Klein-

MacPhee 2002). As a consequence the vertical distribution guild type in this study contains two guilds:

• Pelagic species (P) which occupy the upper portions of the water column with

little direct dependence upon the substrate (e.g., Clupea harengus, Atlantic

herring).

• Demersal species (D) which are closely associated with the bottom (e.g., Gadus

morhua, Atlantic cod).

Reproductive Type

Reproductive type examines the method of reproduction among estuarine fishes.

This guild category was modified from Elliott and DeWailly (1995) with the removal of the egg dispersal and parental care sub-guilds in order to simplify analysis and interpretation of results. This guild category contains three guilds based upon the three reproductive strategies that exist among fishes (Bond 1996):

• Viviparous species (V) produce free-living offspring that develop and obtain

nourishment from within the female’s body (e.g., Embiotocidae, surf perches).

• Ovoviviparous species (W) produce free-living offspring which hatch from eggs

carried within the parent’s body without obtaining nourishment from the parent

(e.g., Syngnathidae, seahorses).

• Oviparous species (O) produce eggs which hatch outside the adult’s body and

undergo a larval stage during ontogeny (e.g., Gadidae, cods).

Egg Dispersal

Egg dispersal examines the method of egg dispersal among oviparous fishes. The category is modified from Elliott and DeWailly (1995) who proposed this as a sub-guild of the oviparous reproductive type. However since oviparous fishes constitute the majority of fishes it was felt that this functional trait was important enough to warrant its own analyses. Viviparous or ovoviviparous which do not release free floating eggs (e.g.,

Syngnathus fuscus, northern pipefish) were removed from analyses. The egg dispersal guild type contains two guilds based upon the two main dispersal strategies in oviparous fishes (Bond 1996):

• Pelagic egg producers (P) allow currents to facilitate the dispersal of eggs;

includes semi-demersal/pelagic eggs which drift with the current above the

substrate (e.g., Urophycis tenuis, white hake or Alosa pseudoharengus, alewife).

• Demersal egg producers (D) which deposit eggs on the substrate minimizing

dispersal (e.g., Menidia menidia, Atlantic silverside).

Residency

Residency guilds examine the seasonal occurrence of species within the fish assemblage sampled. Residency has been assessed by a number of authors investigating seasonal variation of fish communities in a variety of habitats (e.g. Tyler 1971, Methven et al. 2001). The classification system developed by Tyler (1971) has been used for nearshore species previously (Methven et al. 2001) and was adopted for this study. The definition of ‘regular’ species used in this study differs from previous definitions of

‘resident’ species in that these species simply occur in the nearshore area throughout the year and individuals do not necessarily reside there throughout their lives. This distinction is important to avoid confusion in terminology identified by Able et al.

(2002). Species were assigned to each guild based on the presence and absence of species collected throughout the seasonal sampling of this study. The residency guild category contains four guilds based on the seasonal occurrence each species:

• Regular species (R) occur in estuaries throughout the year (e.g., Menidia

menidia, Atlantic silverside).

• Summer Periodic species (SP) frequent estuaries during the warmer months of

the year and are absent during winter (e.g., Urophycis tenuis, white hake).

• Winter Periodic species (WP) occur nearshore during the winter (Liparis

atlanticus, Atlantic snail fish).

• Occasional species (O) occur rarely in estuaries (i.e., less than 10 individuals

collected) and seasonal patterns of occurrence can not be confidently determined

based on low catches.

Maturity

Maturity examines the developmental structure of the fish assemblage and has been modified from the classification used by Methven et al. (2001). Guild membership is based on whether a species inhabits the nearshore environment as juveniles (e.g., nursery species), adults (e.g., foragers) or both (e.g., residents). In order to determine appropriate membership for each species, individuals are compared to the reported size at first spawning given in Table 2.7:

• Juvenile (J) includes species which occupy the nearshore environment prior to

reaching sexual maturity (e.g., Urophycis tenuis, white hake).

• Adult (A) includes species which occupy the nearshore environment after

reaching sexual maturity (e.g., Anguilla rostra, American eel).

• Mixed (J/A) includes species which occupy the nearshore environment during

both juvenile and adult life history stages (e.g., Menidia menidia, Atlantic

silverside).

2.4 Results

2.4.1 Seasonal Variation (Study 1)

A total of 2669 fish representing 18 species and 11 families were collected from six sites during 13 months of sampling in the southwest Bay of Fundy (Table 2.3). Seven species accounted for 96.18% of the total catch. Menidia menidia was the dominant species and represented 53.95% of the total catch. Osmerus mordax, (18.70%), Clupea harengus, (9.25%), Pseudopleuronectes americanus, (3.86%), Microgadus tomcod,

(3.86%), Myoxocephalus scorpius, (3.30%), and Gasterosteus wheatlandi, (3.26%) were the next most abundant species (Table 2.3). Eleven additional species accounted for the remaining 3.82% (Table 2.3).

Temperature and salinity varied seasonally when averaged across the six sites sampled in the southwest Bay of Fundy (Figure 2.2). Highest temperatures occurred from June (11.5˚C) to October (11.4˚C) reaching a maximum of 16.4˚C in August. The lowest temperatures occurred from January (0.4˚C) to March (1.9 ˚C) reaching a minimum in January. Salinity showed a bimodal seasonal pattern with high salinities occurring in September (30.3 ‰) and March (30.7 ‰) followed by low salinities occurring in May (25.5 ‰) and December (24.9 ‰, Figure 2.2).

Species richness (S) and total catches (Ni) were highest from June to October and lowest from January and March (Figure 2.2). This pattern was observed at each of the six sites sampled, although there was considerable variation (Figure 2.3). For example, species richness at McLaren Beach (site 12) ranged from three to eight from June to

October and from zero to one at Brandy Cove (site 2) during the same period. Species richness at all sites from January to April was consistently less than three (Figure 2.3).

Correlations between species richness and temperature throughout the 13 months of sampling were all positive but varied among sites in terms of their significance with the strongest correlation observed at Holts Point (site 3: r = 0.95, n = 13, p = <0.001) and the weakest occurring at Bar Road; a neighbouring site (site 2: r = 0.23, n = 13, p = 0.460,

Table 2.4, Figure 2.1). Correlations between abundance and temperature were strongest at the Digby Ferry Terminal (site 14: r = 0.63, n = 13, p = 0.021) and weakest at Bar

Road (site 2: r = 0.02, n = 13, p = 0.961). Strong correlations were not observed with salinity and species richness or abundance at any of the sites. Results were highly variable with a mixture of both positive and negative correlations at the scales of site and region (Table 2.4). Saint John Harbour exhibited a higher mean richness (S = 5.5 +/-

0.8) and abundance (Ni = 147.3 +/- 33.5) throughout the year compared to

Passamaquoddy Bay (S = 3.7 +/- 0.9, Ni = 58.0 +/- 26.2). Correlations between temperature and species richness were significant in each region (Passamaquoddy Bay: r

= 0.90, n=13, p = <0.001; Saint John Harbour r = 0.62, n = 13, p = 0.024) as well as correlations between temperature and abundance in Saint John Harbour (r = 0.81, n =

13, p = 0.001), but not Passamaquoddy Bay (r = 0.43, n=13, p = 0.143). Correlations

39 with temperature and species richness (r = 0.85, n = 13, p = <0.001) and abundance (r =

0.75, n = 13, p = 0.003) were highest at the bay scale (Table 2.4).

The six sites sampled throughout the year in this study fused into two groups at

38% similarity based on Bray Curtis analysis of species composition and abundance

(Figure 2.4). Adjacent sites did not necessarily group together based on their spatial proximity to each other (Figure 2.4). For example, species composition and abundance at site 3 were more similar to sites 12 and 14 (56% similarity, Figure 2.4) than to sites 1 or 2 (38% similarity) even though site 3 was closer to site 1 (10 km) and 2 (8 km) than sites 12 (70 km) or 14 (74 km, Figure 2.1). Species richness and abundance differed between the two groups (group 1, S=18, Ni=2095; group 2, S=11, Ni=574) largely due to nine species (M. aenaeus, C. lumpus, H. americanus, U. tenuis, P. virens, A. aestivalis,

A. rostrata, G. morhua and S. aquosus) with low catches that were limited to sites 3, 12 and 14 (Figure 2.4). Differences between groups 1 and 2 were also due to substantial differences in mean catches of three relatively common species, M. menidia (429.7 and

50.3), O. mordax (139.3 and 27.0) and C. harengus (0.3 and 82.0, Figure 2.4). These three highly mobile, pelagic schooling species (M. menidia, O. mordax, and C. harengus) accounted for 81.9% of the catch and hence had a considerable influence on the dendogram structure observed in Figure 2.4.

Similarity among sites was also examined using the Bray-Curtis index with a binary data set. This removed the effect of highly abundant species on site similarity and weighed all species equally based on their presence/absence. As a consequence, sites did not group together in the same combinations reported above (Figure 2.4 and 2.5). Spatial proximity was still relatively unimportant in grouping sites given that the highest percent

40 similarity occurred between two distant sites (2 and 13) that were 77 km apart (Figure

2.1). All sites exhibited greater than 50% similarity to each other with the highest similarity occurring between sites 2 and 13 (80%). Sites divided into three main groups with group 1 (site 3) diverging at 51% and groups 2 (sites 2, 12 and 13) and 3 (sites 1 and 14) diverging at 67% similarity (Figure 2.5). The absence of G. aculeatus and O. mordax as well as the presence of three species unique to group 1 (G. morhua, H. americanus, and S. aquosus) were largely responsible for this initial divergence. The absence of C. harengus from group 3, a species found at every site in group 2 (Figure

2.5) was the species primarily responsible for separating groups 2 and 3.

Two seasonal groupings were evident when binary data were analyzed using the

Bray Curtis Index of similarity at scales of site, region and bay (Figure 2.6). A warm water species assemblage (11.3 +/- 1.54˚C, March - December) and a colder water assemblage (2.0 +/- 0.88˚C, January – April, Figure 2.7) occurred at all scales and sites except site 13, although there was considerable variation among sites (Figure 2.6). At the bay scale the two seasonal groupings diverged at 39% similarity (Figure 2.7). The warm water assemblage exhibited a relatively high species richness (S = 18) while the cold water assemblage consisted of relatively few species (S = 3). The three species occurring in the cold water group (O. mordax, M. menidia, P. americanus) were also present in the southwest Bay of Fundy during each of the warmer months, however the remaining 15 species warm water species were absent from the cold water group (Figure

2.7).

Menidia menidia, O. mordax and P. americanus were the only species observed year round during 13 months of sampling in the nearshore area (Figure 2.8). These

41 regular species (i.e., occur year round; terminology of Tyler 1971) ranked among the top five in abundance (Table 2.3). Menidia menidia and O. mordax were also two of only five species collected in which the juvenile and adults stages co-occurred in the nearshore area (Figure 2.8). The summer periodic group (not present in winter) consisted of 11 species, the majority of which were only as juveniles. Microgadus tomcod, G. wheatlandi and G. aculeatus were the only summer periodic species taken in both juvenile and adult stages (Figure 2.8). Alosa aestivalis, A. rostrata, G. morhua and S. aquosus were occasional species having no obvious seasonal patterns due to their low abundances (Table 2.3). A monthly increase in length for some species (M. menidia, P. americanus, M. tomcod and G. aculeatus) suggests that the same individuals may reside nearshore for several successive months (Figure 2.8).

2.4.2 Functional Guilds

The seven most abundant species collected during the seasonal sampling consisted of three marine migrants (C. harengus, P. americanus, M. scorpius), two anadromous species (O. mordax, M. tomcod), one estuarine resident (M. menidia) and one estuarine migrant (G. wheatlandi, Tables 2.5, 2.6). Four of these species occupied pelagic habitats (M. menidia, O. mordax, C. harengus, G. wheatlandi) while the remaining three were demersal (M. tomcod, P. americanus, and M. scorpius). All seven species exhibited an oviparous reproductive type and produced demersal eggs. The three most abundant fishes were regular species occurring year round in the nearshore environment (M. menidia, O. mordax, P. americanus), while the remaining four were

42 summer periodic species being collected only during the warmer months. Four of these fishes utilized the nearshore environment as both adults and juveniles (M. menidia, O. mordax, M. tomcod, G. wheatlandi) while the remaining three species occurred only during the juvenile stage (C. harengus, P. americanus, M. scorpius, Table 2.5 and 2.6).

The guild composition of the seven most dominant species was similar to the overall fish assemblage with some marked differences (Table 2.6). Overall the fish assemblage of the southwest Bay of Fundy was dominated by juvenile (67%), demersal

(61%), marine migrant (50%) species, exhibiting an oviparous reproductive type (100%) and demersal eggs (61%). Also, the majority of species occurred only during the warmer months of the year (occasional 44%, summer periodic 39%).

The number of individuals within each functional guild varied considerably from the species based patterns reported above (Table 2.6). From the perspective of the number of individuals occurring in each guild the fish assemblage was dominated by pelagic (87%), estuarine residents (56%), that occurred year round (regular 76%) in both juvenile and adult stages (80%). These individuals were oviparous (100%) producing pelagic eggs (98%).

2.4.3 Regional Variation (Study 2)

A total of 1372 individuals representing 11 species and 9 families were collected from 48 samples taken at 16 sites (3 hauls/site) in the southern Bay of Fundy between

October 16 and 22, 2004 (Table 2.8). Species richness and abundance varied considerably among sites with the highest species richness observed at site 6 (S = 6), the

highest abundance at site 5 (Ni = 448) and the lowest values for both richness and abundance observed at site 1 (S = 1, Ni = 1, Table 2.9, Figure 2.9). A single dominant species, M. menidia, accounted for 93.9% of the total catch (Table 2.8). Menidia menidia also made up more than 50% of the catch at 12 of the 16 sites (sites 2-3, 5-10,

12, and 14-16, Figure 2.9).

Sites did not group together based upon their spatial proximity to each other when examined using the Bray-Curtis coefficient. For example the highest percent similarity was observed between sites 5 and 16 (91.6%, Figure 2.10) which are 61 km apart (Figure 2.1). Sites were divided into three main groups (Figure 2.10) with group 1 consisting of a single site (site 1) that was 0.9% similar to all other sites due to the of only one species (P. gunnellus, S = 1, Ni = 1). Group 2 consisted of eight sites (sites 2-3,

5-6, 8-9, 14 and 16) and group 3 of seven sites (4, 7, 10-13 and 15) which differed in terms of their species richness and abundance (group 2: S = 11, Ni = 1297; group 3: S =

7, Ni = 74). Differences in abundance were largely driven by M. menidia which was high among sites in group 2 (mean = 155.8) and low among sites in group 3 (mean = 6.0).

The presence of rare species unique to group 2 (G. aculeatus, P. gunnellus, P. pseudoharengus and A. quadracus, Figure 2.10) was also largely responsible for the division. Additionally, groups 2 and 3 were separated in terms of their habitat types with

6 of the 8 sites present in group 2 having a coarse substrate (gravel and rock) and 6 of the 7 sites present in group 3 having a fine substrate (mud and sand, Table 2.1, Figure

2.10).

2.4.4 Tidal and Diel Variation (Study 3)

A total of 1684 fish representing 11 species and 8 families were collected in 78 samples taken over two twenty four hour sampling periods (September 24-25 and

October 1-2, 2004) at Black Beach (Table 2.10). Surface water temperatures for

September (12.2 +/- 0.2˚C) and October (11.3 +/- 0.1˚C) were consistent within each sampling period, but varied significantly between weeks (paired t-test; t1, 24 = 6.231, two tailed critical value = 2.178, p = < 0.001, mean difference 0.5 °C). The dominant species taken were M. menidia, O. mordax and P. americanus. These accounted for 90.91% of the catch in September and 94.86% of the catch in October (Table 2.10).

Significant differences in species richness and abundance were observed with respect to tidal height (low/mid/high), while differences in time of day (day/night) were limited to the second sampling period. Species richness and abundance were on average higher at night than during the day (Table 2.11, mean difference 0.95 species, and 8.3 individuals/haul), with nine species and 938 individuals collected at night and seven species and 746 individuals collected during the day (Table 2.11). The highest catches occurred immediately after dawn and dusk resulting from peaks in the catch of M. menidia during these periods (Figure 2.11). The highest variance in species richness occurred during nocturnal collections while the highest variance in abundance occurred during the day. These findings were variable among sampling periods with dissimilar patterns observed between the first (September 24-25) and second (October 1-2) sampling periods (Table 2.12). Results of three factor ANOVAs for species richness and abundance with respect to sampling period (September 24-25, October 1-2), time of day

(day/night), and tide (low/mid/high), indicated a significant interaction between time of

45 day and sampling period (Table 2.13), with no significant difference observed in species richness or abundance during the first sampling period (September 24-25), while significant differences were observed during the second sampling period (October 1-2,

Table 2.11). With respect to tide, significant differences in both species richness and abundance were observed (Table 2.13). Post-hoc tests identified low tide as having both greater species richness and abundance than the other tidal phases (mid/high), while mid and high tide were not significantly different from each other. Overall, 10 species and

955 individuals were collected at low tide, 6 species and 224 individuals at mid tide and

3 species and 505 individuals at high tide (Table 2.11, Figure 2.11). The lower species richness observed at mid and high tides resulted from an absence of species moving into the intertidal zone (Table 2.11), with only three pelagic species (M. menidia, O. mordax and A. aestivalis) captured at high tide. A strong negative correlation was also observed between species richness and tidal amplitude (r = -0.766, p = <0.001), however due to peaks in abundance largely related to crepuscular interactions and not tidal height, a significant correlation was not observed between abundance and tidal amplitude during the two twenty four hour collections (r = -0.204, p = 0.073). The highest variance in species richness occurred at low tide while the highest variance in abundance occurred at high tide. However these findings were variable among twenty four hour periods with different patterns observed in September and October (Table 2.12).

Tidal height and time of day also had a significant influence on the size structure of the fish assemblage observed. Significantly larger fishes were collected at night as well as during mid and high tides (Table 2.14, Figure 2.12). Differences between night and day fish assemblages resulted from larger fishes migrating inshore at night

46 supplementing the smaller fishes already utilizing the area during the day (Figure 2.12).

Larger mean lengths observed at mid and high tides resulted from an absence of small fishes moving into the intertidal zone (Figure 2.12).

2.5 Discussion

2.5.1 Seasonal Variation

Throughout 13 months of sampling in the southwest Bay of Fundy, a total of 18 species were collected with seven of these accounting for greater than 95 percent of the overall abundance. This level of richness and degree of dominance was common among collections using similar gears in the Acadian zoogeographic region (defined in Briggs

1974), with richness typically ranging from 18 – 24 species, while 5 – 8 of these generally made up over 95 percent of the total abundance (e.g., Ayvazian et al. 1992,

Lazzari et al. 1999, Methven et al. 2001, Able et al. 2002, Wilbur 2004). A number of species were common to the region with A. aestivalis, A. pseudoharengus, C. harengus,

C. lumpus, G. aculeatus, G. wheatlandi, M. aenaeus, M. menidia, O. mordax, and P. americanus regularly found among nearshore habitats in the Gulf of Maine. Due to the high degree of dominance in the assemblage, seasonal variation in abundance was mainly the result of changing distributions and abundances of dominant species at various scales (Gibson et al. 1996), while changes in species richness were largely driven by the presence and absence of additional rare species.

Seasonal variation in species richness and abundance were correlated with water temperature at the scale of months, however variation in salinity had little influence on

47 the assemblage structure observed. Increases in species richness and abundance with increasing temperature were observed among the majority of sites examined. However species richness, composition and abundance were variable among sites similar to other studies incorporating multiple sites when examining seasonal variability (e.g., Able et al.

2002). Seasonal patterns were more evident as sites were combined and examined at the region and bay scales, indicating it may be difficult to characterize an area based upon collections at a single site. Seasonal relationships between species richness and abundance with temperature have been reported for other nearshore habitats in northwest

Atlantic (Lazzari et al. 1999, Methven et al. 2001, Able et al. 2002), and Europe (Gibson et al. 1993). However this pattern may not be universal among all nearshore communities as Jackson and Jones (1999) did not detect a significant correlation between species richness and abundance with temperature over a 10 year period in a temperate region of southern Australia. Although temperature was an important variable in structuring the nearshore assemblage of the southwest Bay of Fundy, variation in species richness and abundance in response to changes in salinity were not apparent among months or sites. Salinity has been shown in previous studies to play a significant role in structuring estuarine communities (Haedrich 1983). The lower reaches of estuaries typically exhibit higher salinities with less variability than the upper reaches and consequently exhibit a higher species richness and abundance derived from fishes of marine origin. Since sites sampled within the southwest Bay of Fundy were all from coastal areas and included only the lower reaches of estuaries, these variations were not observed.

Two distinct seasonal assemblages occurred in the southwest Bay of Fundy, a warm water assemblage from May through December, and cold water assemblage from

January through April. The distinction between these two assemblages was an absence of ichthyofauna during the winter months due to extensive offshore migrations by the majority of nearshore species. Offshore winter migrations of estuarine fishes has been widely observed throughout the northwest Atlantic (Ayvazian et al. 1992, Lazzari et al.

1999, Methven et al. 2001, Able et al. 2002) including areas south of Cape Hatteras which experience relatively little seasonal variability in temperature (Ross et al. 1987,

Monteiro-Neto 1990). The warm water assemblage of the southwest Bay of Fundy was represented by a relatively high species richness and abundance produced largely by recruitment spikes of juvenile fishes, followed by a depopulated cold water assemblage that was represented exclusively by low numbers of M. menidia, O. mordax and P. americanus. Each species present during the winter months occurred year round in the nearshore zone although the majority of individuals migrated to other areas during the winter months with M. menidia and P. americanus migrating offshore while O. mordax largely migrated into rivers to spawn (Collette and Klien-MacPhee 2002). Winter emigration from the nearshore area appears to be largely driven by the avoidance of decreasing temperatures, which commonly drop to fatal levels for many nearshore species throughout the winter months (Schultz et al. 1998, Hales and Able 2001). Spring immigration into the nearshore zone occurs when temperatures reach more favourable levels, coinciding with increases in primary production and spawning migrations of several marine species (Haedrich 1983, Mariani 2001). Seasonal fluctuations in richness and abundance in relation to temperature have been shown to be relatively stable and

49 consistent over large temporal scales, although the composition and relative abundance of specific species within the assemblage may change (Lazzari et al. 1999).

2.5.2 Functional Guilds

Contrasting patterns were often observed when examining contributions made by the number of species versus to the number of individuals in a guild type. Whereas species-based assessments gave dominant and rare species equal weighting, individual- based assessments incorporated the relative abundance of individuals in each guild. The individual-based assessment gave a more comprehensive description of the assemblage, but as a consequence were strongly influenced by the dominant members of the community (i.e., M. menidia).

Ecological Type: approximately half of the species encountered were marine migrants, followed by diadromous, estuarine resident and estuarine migrant species. This pattern is reflected in the estuarine literature as marine migrant species typically dominate nearshore areas (Haedrich 1983, Elliottt and DeWailly 1995, Thiel et al.

2003). However, the pattern shifts once the abundance of individuals are considered with estuarine residents making up the majority of fishes, followed by diadromous, marine migrant and estuarine migrant species. Similar patters were observed by Thiel et al. (2003) where species of marine origin formed the majority in terms of species while estuarine fishes dominated in terms of abundance.

Vertical Distribution: the majority of species collected were demersal (61%), largely due to representative species from cottidae, gadidae and pleuronectidae families

50 which commonly use the nearshore area as a nursery. However the assemblage was overwhelmingly dominated by pelagic fishes in terms of abundance (87%).

Reproductive Type: all of the fishes encountered in the southwest Bay of Fundy were oviparous, the most common reproductive type among teleost fishes. Although viviparous and ovoviviparous reproductive types have been observed in the Acadian region (e.g., Lazzari et al. 1999), they are typically found in very low abundance. These findings are consistent with those made among European estuaries and salt marshes

(Elliott and DeWailly 1995, Mathieson et al. 2000).

Egg Dispersal: the majority of fishes encountered produced demersal eggs, both in terms of species richness (61%) and abundance (98%). This strategy may act as a mechanism to retain eggs in the nearshore area where juveniles can quickly find food and refuge upon hatching. This pattern was also observed among European estuaries by

Elliott and DeWailly (1995) where >60% of fishes produced demersal eggs.

Residency: the majority of species sampled in the nearshore zone were only collected during the summer months, with most of these occurring in low abundances and subsequently classified as occasional species (44%) while the remainder were classified as summer periodic (39%). Regular species subsequently made up the remainder of the community (17%) as winter periodic species were not observed in the southwest Bay of Fundy. While occasional and summer periodic species were the most common, the assemblage was dominated by regular species in terms of abundance

(76%). This is not surprising considering regular species are collected year round and therefore have the greatest potential to continuously supplement catches and achieve the highest abundances. The three most abundant species occurred throughout all four

51 seasons (M. menidia, O. mordax and P. americanus), albeit in relatively low numbers during the winter months. Due to the fact the nearshore zone was largely unoccupied during the winter, which is consistent with other work done by Lazzari et al. (1999) and

Ayvazian et al. (1992) in the Gulf of Maine area as well as Massachusetts where the nearshore zone is largely not utilized during the winter months. The reduced species richness and abundance of nearshore areas during the winter months is due largely to offshore migrations by summer periodic species with only resident species remaining nearshore, leaving a small winter community of low diversity, and abundance comprised of only the most tolerant species (Ayvazian et al. 1992). This is not surprising considering the near zero surface water temperatures common to these regions during the winter months. However the same pattern persists in Virginia (Layman 2000) and the Gulf of Mexico (Ross et al. 1987) where surface temperatures are considerably higher during the same period. Conversely winter periodic species have been commonly observed in more northerly areas such as Newfoundland where Methven et al (2001) collected Liparis liparis predominantly during the coldest months of the year, as well as in Scotland where Greenwood and Hill (2003), observed six winter periodic taxa which also occurred predominantly during the winter months (Merlangius merlangu, Liparis liparis, Liminada liminada, Agonus cataphractus, Myoxocephalus scorpius, and

Pomatoschistus spp.).

Maturity: the nearshore assemblage was largely made up species represented by the juvenile stage (67%), a pattern widely observed among temperate nearshore areas which are generally considered important nursery habitats (Haedrich 1983, Methven et al. 2001, Beck et al. 2003). The remaining species were represented by both juvenile and

52 adults stages, primarily using the nearshore area as spawning habitat (G. wheatlandi, M. menidia), or a migration corridor between marine and freshwater habitats (A. rostrata,

O. mordax, M. tomcod, G. aculeatus). In terms of abundance the assemblage was dominated by species occurring in both the juvenile and adult stages (80%), which is not surprising considering the two most abundant species, M. menidia and O. mordax are collected throughout ontogeny, with M. menidia, spending its entire lifecycle in the nearshore zone while O. mordax commonly uses it for a nursery, foraging as well as a migration corridor to freshwaters during spawning.

2.5.3 Regional Variation

Among the 16 sites sampled throughout October 2004, substrate type had the strongest influence on species composition and abundance, with similar habitats having similar assemblages. This is consistent with previous findings in the Gulf of Maine

(Sogard and Able 1991, Able et al. 2002), and Australia (Jenkins and Wheatley 1998).

Geographic proximity among sites had little influence on the community structure observed as relatively distant sites often exhibited greater similarity than neighbouring ones. Similar patterns were also observed with the seasonal sampling described above as

Holts Point (site 3) and Bay Shore (site 13) exhibited a higher degree of similarity with sites from other regions (Passamaquoddy Bay versus Saint John Harbour) than with their own. Overall, more structurally complex substrates had the greatest richness and abundance with soft sedimentary shores (mud and sand) exhibiting a relatively low diversity and abundance compared to hard sediments (gravel and course rock). These

53 findings are consistent with those of Lazzari and Tupper (2002) who found higher species richness and abundance among more structurally complex nearshore habitats in the Gulf of Maine. Due to the fact substrate type has a strong influence on fish assemblage structure; it may be difficult to gain a comprehensive understanding of spatial variation in a region based solely upon collections at a single site. Additional factors not measured during this study including environmental properties such as toxic substances, oxygen content and light have also been shown to influence the value of specific habitats to finfish and may be important to consider in future research when examining variation in habitat preferences among fishes (Ryder and Kerr 1989, Peters and Cross 1992).

2.5.4 Tidal and Diel Variation

Over a twenty four hour period the predominant changes observed in the nearshore fish assemblage were in response to the tide and time of day, consistent with previous research on small scale variation conducted in other nearshore ecosystems around the world (e.g., Lasiak 1984; South Africa, Gibson et al. 1996; Scotland,

Morrison et al. 2002; New Zealand).

Tidal height played the largest role in structuring the assemblage with significantly higher catches during low tide, averaging 2.2 more species and 14.3 individuals per haul. These findings were similar to previous work by Gibson et al.

(1996) and Lasiak (1984) who also found greater richness and abundance at low tide.

Gibson et al. (1996) attributed the lower diversity observed in high water catches to the

54 fact that they are limited to the pelagic fishes which migrate into the intertidal zone with the rising tide, and therefore many of the demersal fishes which remain in the subtidal regions are excluded from high water sampling. This assertion is supported by the findings of this study as high tide catches consisted exclusively of three pelagic fishes

(M. menidia, O. mordax, A. aestivalis), while low tide catches included these pelagic species, as well as seven additional demersal fishes not observed at high tide (A. americanus, C. lumpus, M. tomcod, M. octodecemspinosus, M. scorpius, P. americanus, and U. tenuis).

In terms of time of day, changes in species richness and abundance were variable, with no significant differences observed between day and night during the first sampling period while significant differences were observed during the second.

Although findings were inconsistent, the results of the second sampling period are consistent with previous work by Lasiak (1984), Nash (1986), Sogard and Able (1994), and Methven et al. (2001), who reported greater catches at night using similar gear in similar habitats; however further research will be required in the Bay of Fundy. Previous studies which have observed differences in richness and abundance between day and night have partially attributed this to visual gear avoidance by fishes during the daytime, thus reducing catch per unit effort (Stoner 1991, Casey and Myers 1998). However, differences between day and night assemblages have still been observed in mudflats where the high turbidity of the water makes visual gear avoidance unlikely (Morrison et al. 2002). Within the southwest Bay of Fundy the nocturnal increase in richness during the second sampling period was largely the result of demersal gadids collected at night

(M. tomcod, P. virens, U. tenuis) which were not captured during the day. This

55 behaviour appears to be characteristic among juvenile gadids and has been observed previously by Methven and Bajdik (1994), Gibson et al. (1996) and Methven et al.

(2001).

Increases in abundance were also observed during twilight hours (two hours immediately following sunrise and sunset). These twilight peaks in abundance were largely attributed to an increase in the numbers of M. menidia, an important prey species in the area. A similar finding was also made by Lasiak (1984) who recorded an increase in the abundance of Pomadasys olivaceus, during the same period. An additional increase in the abundance of M. menidia was also observed in October at 02:00, as a group of large M. saxatilis were observed herding M. menidia inshore while feeding.

Changes in the size distribution of fishes within the assemblage were also observed relative to the tide and time of day. In relation to time of day larger fish were taken at night due to the addition of a larger size class moving inshore, supplementing the individuals which occurred during the day. Similar changes in assemblage structure have been reported previously by Ross et al. (1987), and Gibson et al. (1996), who also found larger individuals moving inshore at night. The reason behind this may be related to foraging behaviour as larger fishes take refuge in deeper water during the day while moving inshore at night to feed on invertebrates as they leave the substrate (Hobson et al. 1981). In relation to tide larger fishes were taken at mid and high tides while smaller fishes were taken at low tide. This variability in length may be due to the fact that hauls made at mid and high water collect only the larger, more mobile fishes which migrate upshore with the tide (Gibson et al 1996), excluding smaller less mobile fishes which remained in the subtidal zone.

2.6 Conclusion

Overall the nearshore fish assemblage of the southwest Bay of Fundy exhibited a high degree of dominance. Species richness and abundance varied seasonally and were strongly correlated with temperature, exhibiting highs in the summer months and lows during winter. The majority of species occurring in the assemblage were demersal, juveniles of marine origin hatching from pelagic eggs and migrating into the nearshore zone during the summer months, although these patterns did not persist once abundance was considered. Regional variation was influenced by substrate type with similar habitats exhibiting similar communities while spatial proximity among sites had little weight on the assemblage. Over a 24 hour period considerable variation in richness and abundance were observed in response to tide and time of day with the greatest diversity observed at low tide while peaks in abundance occurred at twilight. Based on the findings of this study, the time and place sampling is conducted has considerable influence on the community observed with the greatest diversity, abundance and size classes collected at sites with a course substrate, during low tide, at night, and during the summer months, while sampling during alternate periods may substantially underestimate the richness and abundance of the assemblage (Stoner 1991). As a consequence examining communities at multiple scales is a necessity in order to adequately assess patterns and processes responsible for finfish variance.

2.7 Acknowledgements

I would like to acknowledge several people for their assistance during the course of this study. I would like to thank Kevin Shaughnessey, Mark Pokorski, Jason

Casselman, Frederic Vandeperre and Joesph Pratt for their assistance in the field throughout the course of sampling, as well as Mr. Bill Kerr for his time and use of his vehicle. I would also like to thank my supervisors, Dave Methven and Kelly Munkittrick for their guidance and support. Funding was provided by the University of New

Brunswick and the New Brunswick Innovation Foundation.

Site No. Site Name Study Latitude (°N) Longitude (°W) Dominant Substrate† 1 Brandy Cove 1 2 45° 05.095 67° 04.914 Mud 2 Bar Road 1 2 45° 05.984 67° 03.247 Sand 3 Holts Point 1 2 45° 08.834 66° 59.005 Sand 4 Greens Point 2 45° 02.513 66° 53.289 Rock 5 Beaver Harbour 2 45° 04.222 66° 44.527 Gravel 6 Seeleys Cove 2 45° 05.701 66° 38.130 Gravel 7 New River Beach 2 45° 07.936 66° 31.606 Sand 8 Maces Bay 2 45° 06.995 66° 28.720 Gravel 9 Dipper Harbour 2 45° 05.422 66° 25.067 Gravel 10 Chance Harbour 2 45° 07.923 66° 20.917 Sand 11 Black Beach 2 3 45° 09.280 66° 13.737 Sand 12 McLarens Beach 1 2 45° 14.199 66° 06.074 Mud 13 Bay Shore 1 2 45° 14.635 66° 04.600 Sand 14 Digby Ferry Terminal 1 2 45° 15.252 66° 03.758 Rock 15 McNamara Point 2 45° 15.550 66° 01.900 Sand 16 Cranberry Point 2 45° 14.576 66° 00.340 Gravel † Determined visually

Scientific Name Common Name Rank Ni % Cumulative Site Number % 1 2 3 12 13 14

Menidia menidia Atlantic silverside 1 1440 53.95 53.95 Osmerus mordax rainbow smelt 2 499 18.70 72.65 Clupea harengus Atlantic herring 3 247 9.25 81.90 Microgadus tomcod Atlantic tomcod 4 103 3.86 85.76 Pseudopleuronectes americanus winter flounder 4 103 3.86 89.62 Myoxocephalus scorpius shorthorn sculpin 6 88 3.30 92.92 Gasterosteus wheatlandi blackpotted stickleback 7 87 3.26 96.18 Gasterosteus aculeatus threespine stickleback 8 36 1.35 97.53 Alosa pseudoharengus alewife 9 23 0.86 98.39 Myoxocephalus aenaeus grubby 10 10 0.37 98.76 Pollachius virens pollock 11 9 0.34 99.10 Cyclopterus lumpus lumpfish 12 7 0.26 99.36 Hemitripterus americanus sea raven 13 6 0.22 99.59 Urophycis tenuis white hake 13 6 0.22 99.81 Alosa aestivalis blueback herring 15 2 0.07 99.89 Anguilla rostrata American eel 16 1 0.04 99.93 Gadus morhua Atlantic cod 16 1 0.04 99.96 Scophthalmus aquosus windowpane 16 1 0.04 100.00 Totals 2669 100.00 8 6 12 11 9 11

Scale S * ˚C S * ‰ Ni * ˚C Ni * ‰ r P r P r P r P Site 1 0.79 0.001 -0.10 0.749 0.43 0.147 -0.04 0.899 2 0.23 0.460 0.20 0.522 0.02 0.961 0.16 0.602 3 0.95 <0.001 0.07 0.824 0.39 0.182 0.05 0.876 12 0.76 0.003 -0.49 0.089 0.52 0.070 -0.64 0.017 13 0.34 0.251 -0.03 0.932 0.43 0.146 -0.06 0.840 14 0.65 0.016 0.06 0.834 0.63 0.021 0.02 0.956 mean 0.62 -0.05 0.40 -0.09

Region PB 0.90 <0.001 0.06 0.838 0.43 0.143 0.03 0.928 SJH 0.62 0.024 -0.03 0.925 0.81 0.001 -0.33 0.269 mean 0.76 0.02 0.62 -0.15

Bay 0.85 <0.001 -0.38 0.195 0.75 0.003 -0.23 0.441

Scientific Name Functional Guild Category Ecological Vertical Reproductive Egg Residency Maturity Type Distribution Type Dispersal Anguilla rostrata DA D O P O A Alosa aestivalis DA P O P O J Alosa pseudoharengus DA P O P SP J Clupea harengus MM P O D SP J Osmerus mordax DA P O D R J/A Gadus morhua MM D O P O J Microgadus tomcod DA D O D SP J/A Pollachius virens MM D O P O J Urophycis tenuis MM D O P O J Menidia menidia ER P O D R J/A Gasterosteus aculeatus DA P O D SP J/A Gasterosteus wheatlandi EM P O D SP J/A Myoxocephalus aenaeus ER D O D SP J Myoxocephalus scorpius MM D O D SP J Hemitripterus americanus MM D O D O J Cyclopterus lumpus MM D O D O J Scophthalmus aquosus MM D O P O J Pseudopleuronectes americanus MM D O D R J

Functional Guild Types Ecological Vertical Reproductive Egg Residency Maturity Type Distribution Type Dispersal

S Ni S Ni S Ni S Ni S Ni S Ni MM: 0.50 0.19 D: 0.61 0.13 V: 0.00 0.00 D: 0.61 0.98 R: 0.17 0.76 J: 0.67 0.20 MS: 0.00 0.00 P: 0.39 0.87 W: 0.00 0.00 P: 0.39 0.02 SP: 0.39 0.23 A: 0.06 0.00 ER: 0.11 0.56 O: 1.001.00 WP:0.00 0.00 J/A: 0.28 0.80 EM: 0.06 0.03 O: 0.440.01 FM: 0.00 0.00 FS: 0.00 0.00 DA: 0.33 0.22 Totals 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

Table 2.7: Estimated size and age of maturity for fishes collected during seasonal sampling in the southwest Bay of Fundy.

Species Size at Maturity % Mature Source Anguilla rostrata 280 – 450 mm 100.0 Colette and Klein-MacPhee (2002) Menidia menidia 50 – 80 mm 44.2 Able and Fahay (1998) Clupea harengus 250 – 280 mm TL 0.0 O'Brien et al. (1993), Boyar (1968) Alosa aestivalis 3 to 6 years *0.0 Colette and Klein-MacPhee (2002) Alosa pseudoharengus 250 – 310 mm 0.0 Jessop et al. (1983), Scott and Scott (1988) Myoxocephalus aenaeus < 73 mm TL † 0.0 Ennis (1969) Myoxocephalus scorpius 2 – 8 years *0.0 Ennis (1970) Cyclopterus lumpus 5 years, 127 mm 0.0 Cox (1920), Davenport and Thorsteinsson (1989) Gadus morhua 320 – 360 mm 0.0 O’Brien et al. (1993) Microgadus tomcod 170 mm 4.9 Schaner and Sherman (1960) Pollachius virens 460 – 600 mm 0.0 Beacham (1982), Beacham (1983), Mayo et al. (1989) Urophycis tenuis 330 – 470 mm 0.0 Beacham (1983),O’Brien et al. (1993) Gasterosteus aculeatus 40 mm 8.3 Colette and Klein-MacPhee (2002) Gasterosteus wheatlandi 33 – 37 mm 55.2 Rowland (1983) Hemitripterus americanus 28 – 36 mm 0.0 Beacham (1982) Osmerus mordax 120 mm 4.0 Scott and Crossman (1973) Pseudopleuronectes 200 – 250 mm 0.0 Scott and Scott (1988) americanus Scophthalmus aquosus 210 – 225 mm 0.0 O'Brien et al. (1993)

*Captured young of the year assumed to be immature. † Smallest mature specimen on record

Table 2.8: Relative abundance of fishes collected by seine during the regional sampling at 16 sites in the southern Bay of Fundy in October.

Scientific Name Common Name Ni Rank % Cumulative %

Menidia menidia Atlantic silverside 1288 1 93.88 93.88 Pseudopleuronectes americanus winter flounder 27 2 1.97 95.85 Cyclopterus lumpus lumpfish 19 31.38 97.23 Gasterosteus wheatlandi blackspotted stickleback 16 4 1.17 98.40 Myoxocephalus scorpius shorthorn sculpin 7 5 0.51 98.91 Osmerus mordax rainbow smelt 5 6 0.36 99.27 Ammodytes americanus inshore sandlance 3 7 0.22 99.49 Pholis gunnellus rock gunnel 3 7 0.22 99.71 Gasterosteus aculeatus threespine stickleback 2 9 0.15 99.85 Apeltes quadracus fourspine stickleback 1 10 0.07 99.93 Alosa pseudoharengus alewife 1 100.07 100.00 Totals 1372 100.00

Table 2.9: Species collected by seine at each of the 16 sites during the regional sampling in the southern Bay of Fundy, October 16-22, 2004.

Scientific Name Common Name Site Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Menidia menidia Atlantic silverside Pseudopleuronectes americanus winter flounder Cyclopterus lumpus lumpfish Gasterosteus wheatlandi blackspotted stickleback Myoxocephalus scorpius shorthorn sculpin Osmerus mordax rainbow smelt Ammodytes americanus inshore sandlance Pholis gunnellus rock gunnel Gasterosteus aculeatus threespine stickleback Apeltes quadracus fourspine stickleback Alosa pseudoharengus alewife Totals 1 5 6 3 3 4 2 1 1 2 3 2 3 2 2 4

Table 2.10: Species collected by seine over two twenty four hour sampling periods at Black Beach, New Brunswick (site 11). Ni indicates the number of individuals collected for each species. September 24-25, 2004 Scientific Name Common Name Ni Rank % Cumulative Menidia menidia Atlantic silverside 491 1 63.77 63.77 Osmerus mordax rainbow smelt 125 2 16.23 80.00 Pseudopleuronectes americanus winter flounder 84 3 10.91 90.91 Alosa aestivalis blueback herring 44 4 5.71 96.62 Myoxocephalus scorpius shorthorn sculpin 15 5 1.95 98.57 Urophycis tenuis white hake 6 6 0.78 99.35 Microgadus tomcod Atlantic tomcod 3 7 0.39 99.74 Cyclopterus lumpus lumpfish 1 8 0.13 99.87 Pollachius virens pollock 1 8 0.13 100.00

October 1-2, 2004 Scientific Name Common Name Ni Rank % Cumulative Menidia menidia Atlantic silverside 625 1 68.38 68.38 Osmerus mordax rainbow smelt 143 2 15.65 84.03 Pseudopleuronectes americanus winter flounder 99 3 10.83 94.86 Myoxocephalus scorpius shorthorn sculpin 21 4 2.30 97.16 Alosa aestivalis blueback herring 18 5 1.97 99.12 Myoxocephalus octodecemspinosus longhorn sculpin 6 6 0.66 99.78 Ammodytes americanus inshore sandlance 2 7 0.22 100.00

Effect Variables September October Overall n S N n S N n S N i i i aestivalis A. A. americanus lumpus C. M. menidia M. tomcod M. octodecemspinosus scorpius M. O. mordax P. virens P. americanus U. tenuis

Time Day 21 5 469 21 7 277 42 7 746 ● ● ● ● ● ● ● of Day Night 18 9 301 18 5 637 36 9 938 ● ● ● ● ● ● ● ● ● Total 39 9 770 39 7 914 78 11 1684

Tidal High 12 3 372 12 3 133 24 3 505 ● ● ● Height Mid 12 5 45 15 4 179 27 6 224 ● ● ● ● ● ● Low 15 8 353 12 7 602 27 10 955 ● ● ● ● ● ● ● ● ● ● Total 39 9 770 39 7 914 78 11 1684

Effect Variables September October Overall

n S Ni n S Ni n S Ni Time Day 21 1.329 3666.933 21 2.062 1111.162 42 1.768 2352.186 of Day Night 18 3.310 437.859 18 1.320 1419.781 36 2.256 991.883

Tidal High 12 0.333 6402.364 12 0.992 338.083 24 0.636 3327.172 Height Mid 12 2.114 8.205 15 1.238 270.638 27 1.088 166.370 Low 15 0.992 411.838 12 1.970 2839.788 27 1.986 1605.088

Source df MS F-ratio P Species Richness† PERIOD 1 0.082 0.696 0.407 TOD 1 2.325 19.775 <0.001 TIDE 2 3.507 29.826 <0.001 PERIOD*TOD 1 0.49 4.163 0.045 PERIOD*TIDE 2 0.013 0.113 0.894 TOD*TIDE 2 0.012 0.102 0.903 PERIOD*TOD*TIDE 2 0.055 0.472 0.626 Error 66 0.118

Abundance‡ PERIOD 1 0.041 0.169 0.682 TOD 1 4.02 16.56 <0.001 TIDE 2 2.962 12.2 <0.001 PERIOD*TOD 1 2.516 10.364 0.002 PERIOD*TIDE 2 0.27 1.114 0.334 TOD*TIDE 2 0.109 0.449 0.640 PERIOD*TOD*TIDE 2 0.507 2.088 0.132 Error 66 0.243 † statistics calculated using √(x+0.5) ‡ statistics calculated using log10(x+1)

Effect Variables Length (mm, SL) Kruskal-Wallis ANOVA n mean variance df n K-W P Time Day 746 59.84 127.077 1 1684 327896.5 0.027 of Day Night 938 65.45 721.313

Tidal High 505 65.57 330.103 2 1684 132.1 <0.001 Height Mid 224 76.29 711.525 Low 955 58.46 415.194

Figure 2.1: Chart of the southwest Bay of Fundy indicating sample sites used during this investigation. Specific information for each site is listed in Table 2.1.

14 20 31 30 12 16 10 29 12 8 28 8 6 27

4 (‰) Salinity 4 26 Temperature (°C)

Species Richness (S) Richness Species 2 0 25

0 24

600 20 31

500 16 30 ) i 29 400 12 28 300 8 27

200 4 (‰) Salinity

Abundance (N 26 Temperature (°C) Temperature 100 0 25

0 24 ASONDJFMAMJ JA

Bay of Fundy

12 500 10 400 8 300 6 200

4 Abundance

Species Richness Species 2 100

0 0 ASONDJFMAMJ JA ASONDJFMAMJ JA Region Passamaquoddy Bay (sites 1-3) Saint John Harbour (sites 12-14) 10 400 10 400

8 300 8 300

6 6 200 200 4 4 Abundance 100 Abundance 100 2 2 Species Richness Species Richness 0 0 0 0 ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA Site

8 Site 1 Site 2 Site 3 Site 12 Site13 Site 14 6

Species Richness 0 300

200

100 Abundance 0 ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA

Figure 2.3: Seasonal patterns of species richness and abundance at site, region and bay scales in the southwest Bay of Fundy.

Figure 2.6: Dendograms identifying seasonal assemblage groupings at the site, region and bay scales in the southwest Bay of Fundy as indicated by the Bray-Curtis index of similarity using binary data. Winter grouping (January to April) is indicated by closed circles.

Regular Species Summer Periodic Species 500 150 50 250 M. menidia O. mordax P. americanus C. harengus n = 1440 n = 499 n = 103 n = 247 400 120 40 200

300 90 30 150

200 60 20 100 Abundance

100 30 10 50

0 0 0 0

125 200 150 75 M. menidia O. mordax P. americanus C. harengus

100 160 120 60

75 120 90 45

50 80 30

SL (mm) 60

25 40 30 15

0 0 0 0 ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA Summer Periodic Species 50 75 50 25 M. tomcod M. scorpius G. wheatlandi G. aculeatus n = 88 n = 87 n = 36 40 n = 103 60 40 20

30 45 30 15

20 30 20 10 Abundance

10 15 10 5

0 0 0 0

300 100 50 75 M. tomcod M. scorpius G. wheatlandi G. aculeatus

240 80 40 60

180 60 30 45

120 40 20 30 SL (mm)

60 20 10 15

0 0 0 0 ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJ FMAMJ JA ASONDJ FMAMJ JA Figure 2.8: Standard length (SL) of individual fish in relation to month of collection. Dotted line indicates the approximate size of first spawning. 79

Summer Periodic Species 25 25 25 25 A. pseudoharengus M. aenaeus P. virens C. lumpus n = 23 n = 9 n = 7 20 20 n = 10 20 20

15 15 15 15

10 10 10 10 Abundance

5 5 5 5

0 0 0 0

100 75 100 50 A. pseudoharengus M. aenaeus P. virens C. lumpus

80 60 80 40

60 45 60 30

40 30 40 20 SL (mm)

20 15 20 10

0 0 0 0 ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA ASONDJFMAMJ JA Summer Periodic Species

25 25 H. americanus U. tenuis

20 n = 620 n = 6

15 15

10 10 Abundance

5 5

0 0

75 100 H. americanus U. tenuis

60 80

45 60

30 40 SL (mm) SL

15 20

0 0 ASONDJ FMAMJ JA ASONDJFMAMJ JA Figure 2.8: Continued.

2 Species Richness Species 0 500

400

300

200 Abundance 100

0 100

40 M. menidia M.

% Composition 20

0 1 2 3 4 5 6 7 8 9 10111213141516 Site

Figure 2.9: Species richness, abundance and percent composition of M. menidia from 16 sites sampled in the southwest Bay of Fundy between October 16 and 22, 2004.

September 24-25 2004 8 8 )

i 7

6 6

4 4

2 2 Species richness (S) richness Species Cumulative abundance (N abundance Cumulative

0 0 50 100 150 200 250 300 350 0 October 1-2 2004 8 8 ) Tidal amplitude (m) amplitude Tidal i 7

6 6

4 4

Species richness (S) richness Species 2 Cumulative abundance (N abundance Cumulative

0 0 50 100 150 200 250 300 350 0 18 22 2 6 10 14 18 18 22 2 6 10 14 18 Time of Day (hrs)

Figure 2.11: Species richness and abundance in relation to tidal amplitude from samples taken over two twenty four hours periods on September 24-25 and October 1- 2, 2004. Night hours are indicated by the thatched area.

Diel Tidal

Night Mean: 65.46 +/- 0.88 mm High Mean: 65.56 +/- 0.81 mm 60 Median: 63 mm 60 Median: 63 mm

40 40 Frequency 20 20

0 0 Day Mean: 59.84 +/- 0.41 mm Mid Mean: 75.29 +/- 1.78 mm 60 Median: 62 mm 60 Median: 66.5 mm

40 40 Frequency 20 20

0 0 0 50 100 150 200 250 Standrad Length (mm) Low Mean: 58.46 +/- 0.66 mm 60 Median: 60 mm

Frequency 20

0 0 50 100 150 200 250 Standrad Length (mm)

2.8 Literature Cited

Able, K.W., and M.P. Fahay. 1998. The First Year in the Life of Estuarine Fishes in the Middle Atlantic Bight. Rutgers University Press, New Jersey. 342 pp.

Able, K.W., M.P. Fahay, K.L. Heck, C.T. Roman, M.A. Lazzari, and S.C. Kaiser. 2002. Seasonal distribution and abundance of fishes and decapod crustaceans in a Cape Cod estuary. Northeastern Naturalist. 9(3): 285-302.

Ayvazian, S.G., L.A. Deegan, and J.T. Finn. 1992. Comparison of habitat use by estuarine fish assemblages in the Acadian and Virginian provinces. Estuaries. 15(3): 368-383.

Beacham, T.D. 1982. Median length at sexual maturity of halibut, cusk, longhorn sculpin, ocean pout, and sea raven in the Maritimes area of the Northwest Atlantic. Canadian Journal of Zoology. 60: 1326-1330.

Beacham, T.D. 1982. Growth of pollock (Pollachius virens) on the Scotian Shelf in the Northwest Atlantic Ocean. Canadian Technical Report of Fisheries and Aquatic Sciences. 969: 23pp.

Beacham, T.D. 1983. Variability in size or age at sexual maturity of white hake, pollock, longfin hake, and silver hake in the Canadian Maritimes area of the Northwest Atlantic Ocean. Canadian Technical Report of Fisheries and Aquatic Sciences. 1157.

Bond, C.E. 1996. Biology of Fishes. Saunders College Publishing, New York. 768 pp.

Boyar, H.C. 1968. Age, length and gonadal stages of herring from Georges Bank and the Gulf of Maine. International Commission for the Northwest Atlantic Fisheries Research Bulletin. 5: 49–61.

Bray, J.R. and J.T. Curtis. 1957. An ordination of the upland forest communities of southern Wisconsin. Ecological Monographs. 27: 325-349.

Briggs, J.R. 1974. Marine Zoogeography. McGrawHill, New York. 475 pp.

Colette, B.B., and G. Klein-MacPhee. 2002. Bigelow and Schroeder’s Fishes of the Gulf of Maine. Smithsonian Institution Press. Washington, DC. 748 pp.

Cox, P. 1920. Histories of new food fishes. II. The lumpfish. Bulletin of the Biological Board of Canada. 2: 1–28.

Davenport, J. and V. Thoresteinsson. 1989. Observations on the colours of lumpsuckers, Cyclopterus lumpus L. Journal of Fish Biology. 35: 829–838.

Dye, A.H. 1998. Dynamics of rocky intertidal communities: analyses of long time series from South African shores. Estuaries, Coastal and Shelf Science. 46: 287-305.

Elliot, M., and F. DeWailly. 1995. The structure and components of European estuarine fish assemblages. Netherlands Journal of Aquatic Ecology. 29(3-4): 397-417.

Elliott, M., and K.L. Hemingway. 2002. Fishes in Estuaries. Blackwell Science. Oxford, UK. 636 pp.

Ennis, G.P. 1969. Occurrences of the little sculpin, Myoxocephalus aeneus, in Newfoundland waters. Fisheries Research Board of Canada.

Ennis, G.P. 1970. Age, growth and sexual maturity of the shorthorn sculpin, Myoxocephalus scorpius, in Newfoundland waters. Journal of the Fisheries Research Board of Canada. 27: 2155–2158.

Field, J.G., K.R. Clarke, and R.M. Warwick. 1982. A practical strategy for analyzing multispecies distribution patterns. Marine Ecology Progress Series. 8: 37-52.

Gibson, R.N., A.D. Ansell, and L. Robb. 1993. Seasonal and annual variations in abundance and species composition of fish and macrocrustacean communities on a Scottish sandy beach. Marine Ecology Progress Series. 98: 89-105.

Gibson, R.N., L. Robb, M.T. Burrows, and A.D. Ansell. 1996. Tidal, diel and longer term changes in the distribution of fishes on a Scottish sandy beach. Marine Ecology Progress Series. 130: 1-17.

Haedrich, R.L. 1983. Estuarine Fishes. In Estuaries and Enclosed Seas. Ecosystems of the World 26 (Ketchum, B.H., ed.). Elsevier Scientific, New York. pp. 183-207.

Hales, L. and K. Able. 2001. Winter mortality, growth, and behavior of young-of-the- year of four coastal fishes in New Jersey (USA) waters. Marine Biology. 139: 45- 54.

Jackson, G., and G.K. Jones. 1999. Spatial and temporal variation in nearshore fish and macroinvertebrate assemblages from a temperate Australian estuary over a decade. Marine Ecology Progress Series. 182: 253-268.

Jenkins, G.P., and M.J. Wheatley. 1998. The influence of habitat structure on nearshore fish assemblages in a southern Australian embayment: Comparison of shallow seagrass, reefalgal and unvegetated sand habitats, with emphasis on their importance to recruitment. Journal of Experimental Maine Biology and Ecology. 221: 147-172.

Jessop, B.M., Anderson, W.E. and A.H Vromans. 1983. Lifehistory data on the alewife and blueback herring of the Saint John River, New Brunswick, 1981. Canadian Data Report of Fisheries and Aquatic Sciences. 42: 37p.

Lasiak, T. 1984. Structural aspects of the surf-zone fish assemblage at King’s Beach, Algoa Bay, South Africa: Short-term fluctuations. Estuarine, Coastal and Shelf Sciences. 18: 347-360.

Lazzari, M.A. and B. Tupper. 2002. Importance of shallow water habitats for demersal fishes and decapod crustaceans in Penobscot Bay, Maine. Environmental Biology of Fishes. 63: 57-66.

Lobry, J., L. Mourand, E. Rochard and P. Elie. 2003. Structure of the Gironde estuarine fish assemblages: a comparison of European estuaries perspective. Aquatic Living Resources. 16: 47-58.

Lotze, H., and I. Milewski. 2002. Two Hundred Years of Ecosystem and Food Web Changes in the Quoddy Region, Outer Bay of Fundy. Conservation Council of New Brunswick. Fredericton, NB. Canada. 188 pp.

Mariani, S. 2001. Can spatial distribution of ichthyofauna describe marine influence on coastal lagoons? A Central Mediterranean Case Study. Estuarine, Coastal and Shelf Science. 52: 261-267.

Mayo, R.K., McGlade, J.M. and S.H. Clark. 1989. Patterns of exploitation and biological status of pollock (Pollachius virens) in the Scotian Shelf, Georges Bank,

and the Gulf of Maine area. Journal of Northwest Atlantic Fishery Science. 9: 1336.

McHugh, J.L. 1967. Estuarine nekton. In Estuaries. (Lauff, G.H. ed.). American Association For the Advancement of Science, Washington, DC. 83: 581-620.

McLusky, D.S., and M. Elliott. 2004. The Estuarine Ecosystem: Ecology, Threats and Management, 3rd Ed. Oxford University Press, Toronto. 222pp.

Methven, D.A., and C. Bajdik. 1994. Temporal variation in size and abundance of juvenile Atlantic cod (Gadus morhua) at an inshore site off eastern Newfoundland. Canadian Journal of Fisheries and Aquatic Sciences. 51: 78-90.

Methven, D.A., R.L. Haedrich, and G.A. Rose. 2001. The fish assemblage of a Newfoundland estuary: Diel, monthly and annual variation. Estuarine, Coastal and Shelf Sciences. 52: 669-687.

O’Brien, L., Burnett, J. and R.K. Mayo. 1993. Maturation of nineteen species of finfish off the northeast coast of the United States, 1985 – 1990. National Oceanic and Atmospheric Administration Technical Report National Marine Fisheries Service. 113: 166.

Peters, D.S., and Cross, F.A. 1991. What is coastal fish habitat? In Stemming the tide of coastal fish habitat loss. Edited by R.H. Stroud. National Coalition for Marine Conservation, Savannah, Ga. pp. 17–22.

Piatt, J.F., A.B. Kettle, and A.A. Abookire. 1999. Temporal and geographic variation in fish communities of lower Cook Inlet, Alaska. Fishery Bulletin. 97(4): 962-977.

Pittman S.J., and C.A., McAlpine. 2003. Movements of marine fish and decapod crustaceans: Process, theory and application. Advances in Marine Biology. 44: 205-294.

Ryder, R.A., and S.R. Kerr. 1989. Environmental priorities: placing habitat in hierarchic perspective. In Proceedings of the National Workshop on Effects of Habitat Alteration on Salmonid Stocks, 6–8 May 1987, Nanaimo, B.C. Edited by C.D. Levings, L.B. Holtby, and M.A. Henderson. Canadian Special Publication Fisheries and Aquatic Science. 105: 2–12.

Rowland, W.J. 1983. Interspecific aggression and dominance in Gasterosteus. Environmental Biology of Fishes. 8: 269–277.

Scott, W.B., and M.G. Scott. 1988. Atlantic Fishes of Canada. Canadian Bulletin of Fisheries and Aquatic Sciences. 219: 731 pp.

Schaner, E., and K. Sherman. 1960. Observations on the fecundity of the tomcod, Microgadus tomcod. Copeia. 1960: 347–348.

Schneider, D.C. 1994. Quantitative Ecology: Spatial and Temporal Scaling. Academic Press. San Diego. 402 pp.

Schultz, E.T., D.O. Conover, and A. Ehtisham. 1998. The dead of winter: size- dependent variation and genetic differences in seasonal mortality among Atlantic silverside (Atherinidae: Menidia menidia) from different latitudes. Canadian Journal of Fisheries and Aquatic Sciences. 55: 1149-1157.

Scott, W.B., and E.J. Crossman. 1973. Freshwater fishes of Canada. Fisheries Research Board of Canada Bulletin. 184pp.

Scott, W.B., and M.G. Scott. 1988. Atlantic Fishes of Canada. Canadian Bulletin of Fisheries and Aquatic Sciences. 219pp.

Sogard, S.M., and K.W. Able. 1991. A comparison of eelgrass, sea lettuce macroalgae, and marsh creeks as habitats for epibenthic fishes and decapods. Estuarine, Coastal and Shelf Sciences. 33: 501-519.

Thomas, M.L.H., D.C. Arnold, and A.R.A. Taylor. 1983. Rocky intertidal communities. In Marine and Coastal Systems of the Quoddy Region, New Brunswick. (Thomas, M.L.H. ed.). Canadian Special Publication of Fisheries and Aquatic Sciences. 64: 306 pp.

Trites, R.W., and C.J. Garrett. 1983. Physical oceanography of the Quoddy region. In Marine and Coastal Systems of the Quoddy Region, New Brunswick. (Thomas, M.L.H. ed.). Canadian Special Publication of Fisheries and Aquatic Sciences. 64: 306 pp.

Tyler, A.V. 1971. Periodic and resident components in communities of Atlantic fishes. Journal of the Fisheries Research Board of Canada. 28: 935-946.

Whitfield, A.K. 1999. Ichthyofaunal assemblages in estuaries: A South African case study. Reviews in Fish Biology and Fisheries. 9: 151-186.

3 CHAPTER 3: LATITUDINAL VARIATION IN TAXONOMIC AND

FUNCTIONAL GUILD STRUCTURE OF NEARSHORE FISH ASSEMBLAGES

OF THE NORTHWEST ATLANTIC

3.1 Abstract

The purpose of this study was to examine latitudinal variation in taxonomic and functional guild structure for nearshore fish communities of the NWA by examining 15 studies conducted between 47°N and 35°N which utilized comparable sampling protocols. A total of 56 families and 110 species were observed among 15 nearshore areas in the NWA. Taxa followed a unimodal pattern with respect to latitude reaching a peak at the southern edge of Cape Cod (41.33°N) to New Jersey (39.54°N). Cluster analyses indicated four main geographic groupings among taxa which were analogous to those identified by Briggs (1974). There were clear distinctions made between the

Labrador, Acadian and Virginian provinces, as well as an additional grouping for the northern portion of the Virginian province which exhibited elevated richness due to its function as an ecotone. In terms of overall guild structure NWA nearshore fish assemblages were dominated by marine migrant species (MM: 46.4%) followed by estuarine residents (ER: 26.4%). The majority of these fishes were demersal (D: 63.6%) utilizing an oviparous reproductive strategy (O: 95.5%) and produced pelagic eggs (P:

57.3%). The majority of these species occurred either infrequently or only during the warmer months of the year (O: 47.9%, SP: 36.1%) occupying the nearshore area exclusively during the juvenile stages (J: 54.0%). Clear latitudinal gradients were identified for several functional guilds with significant changes in the proportions of marine migrant, estuarine resident and diadromous fishes as well as variation in the prevailing means of egg dispersal and proportion of periodic species.

3.2 Introduction

Nearshore coastal environments are widely recognized as regions of high productivity which support high densities of biomass. In terms of fish habitat these areas serve as nursery grounds for juveniles, as feeding and spawning sites for adults, as well as migratory routes for diadromous species (McHugh 1967, Haedrich 1983, Elliott 2002,

Beck et al. 2003). The potential importance of nearshore areas to finfish recruitment throughout the Northwest Atlantic has been highlighted by several authours (NWA, e.g.,

Haedrich 1983, Hoss and Thayer 1993, Beck et al. 2003), and as a consequence a number of studies have been conducted to quantify the composition and spatiotemporal variability of many of these communities (e.g., Ayvazian et al. 1992, Lazzari et al. 1999,

Layman 2000, Methven et al. 2001). These investigations have identified a number of characteristic features regarding the composition and structure of nearshore communities in the NWA, such as seasonal variability with respect to temperature, as well as an overall dominance of juveniles. However, until recently it was difficult to make observations and characterize structure over large spatial scales. Using the body of information now available it is possible to conduct meta-analyses in order to examine large scale spatial processes and establish how nearshore communities are structured throughout the NWA.

Traditionally our understanding of nearshore fish communities has largely been focused on the analysis of taxonomic divisions (i.e., the presence, abundance and/or biomass of species). This understanding has been extended over the past decade by analyzing the ecological structure of nearshore systems through the use of functional guilds (e.g., Elliot and DeWailly 1995, Whitfield 1999, Mathieson et al. 2000, Thiel et

94 al. 2003). In essence, functional guilds are used to summarize the ecological structure of a community by grouping species according to similarities in specific biological and ecological traits deemed important by the investigator (Brown 2004). This approach allows for the creation and testing of models concerning the ecological structure of a system which may not be possible when examining taxonomic attributes alone. In addition to this, since the functional guild approach is independent of the taxonomic classification it facilitates cross-site comparison between communities which may support unique biota and thus could not be readily compared based upon phylogenic relationships (Gitay and Noble 1997).

Functional guilds have been used extensively in avian research since they were first introduced in the late 1960’s (Root 1967, e.g., Szaro 1986, O'Connell et al. 2000,

Bishop and Myers 2005). This approach has since been adopted in several other biological fields receiving particular attention in plant ecology (e.g., Shugart 1997,

Reich et al. 2003). With respect to estuarine ecosystems, the use of functional guilds was first proposed by McHugh (1967), and has been further developed by several authors including Haedrich (1983), Elliot and DeWailly (1995), Whitfield (1999) and Thiel et al.

(2003). To date, the functional guild approach has largely been applied to fish in

European estuaries (e.g., Elliott and DeWailly 1995, Mathieson et al. 2000, Thiel et al.

2003), with limited use in North America. Within the NWA, the use of functional guilds has been rare and the information presented often incidental to the main focus of the investigation (e.g., Tyler 1971, Able et al. 2002, Methven et al. 2001). Also due to the differing methods used to address similar functional traits (e.g., Able 2002, Nordlie

2003), existing research lacks the consistent criterion and terminology necessary to

95 facilitate comparisons among estuaries across a large spatial scale. In order to develop a better understanding of how different functional traits vary spatially in the NWA, a large scale comparison using consistent criteria and terminology is required.

The purpose of this study was to examine latitudinal variation in nearshore fish communities of the NWA. The objectives were to examine latitudinal variation in: 1) taxonomic structure and, 2) functional guild composition.

3.3 Materials and Methods

3.3.1 Sources of Data

Community data was incorporated from 15 nearshore studies conducted throughout the NWA ranging from Newfoundland, Canada (47° N) south to Virginia,

USA (36° N, Figure 3.1), encompassing the Labrador, Acadian, and Virginian zoogeographic provinces; as defined in Briggs (1974).

In order to focus on large scale spatial variation throughout the NWA and avoid confounding influences from additional spatiotemporal processes, nearshore studies were selected for analysis primarily due to similarities in sampling protocols. Previous research on nearshore communities have identified significant sources of spatiotemporal variation resulting from patterns in seasonal and diel usage by finfish as well as variation in capture efficiency of various gear types (e.g., Ayvazian et al. 1992, Lazzari et al.

1999, Methven et al. 2001). In order to compensate for these factors sampling protocols were limited to those which: a) spanned a minimum of April to November sampling at least every two months to increase the likelihood of capturing periodic species, b) were

96 carried out during daylight hours reducing the likelihood of enhancing richness resulting from exclusively nocturnal species (nocturnal collections omitted from analyses for

Methven et al. 2001 and Methven unpublished), and c) utilized beach seines of various sizes and/or shallow water trawls (<5m depth) to standardize depth and capture efficiencies and facilitate cross-site comparisons. To maximize the quantity of studies used in the analyses the current assessment ignores large scale temporal variability resulting from the comparison of studies conducted over three decades, as well as variability resulting from differences in habitats type.

3.3.2 Data Analyses

Species and abundance data were assembled for each of the 15 nearshore areas examined in the NWA. Taxonomic similarities in community structure were analyzed at the family and species levels of organization using the Bray-Curtis coefficient (Bray and

Curtis 1957). Data from each study were combined producing a binary matrix

(presence/absence of taxa) for family and species data, giving dominant and rare species equal weighting (Field et al. 1982). Sites were then clustered into groups using dendograms based upon the relative taxonomic similarity of their communities, so that sites within each group shared a greater similarity to each other than sites from other groups.

In order to examine changes in ecological structure with latitude, functional guilds were developed to classify species from each site into discrete groups (guilds) based upon shared biological and ecological characteristics. Each species examined was

97 assigned to a single guild within each of six guild types described below. The proportional contributions made by both the number of species and the number of individuals to each guild were calculated in order to facilitate cross-site comparison and standardize for sampling effort. Scatter plots and subsequent regressions were then produced for each of the 21 guilds against latitude using Systat 11 software. Regression lines were fitted using simple linear, simple exponential or Gaussian peak curves based on r2.

3.3.3 Functional Guild Classification

The following consists of a brief overview of guild classification, further detail can be found in section 2.3.5.

Ecological Type

• Marine Migrants (MM) spawn in the marine environment and typically make

extensive use of estuaries as a foraging ground or nursery area during the

juvenile stages before migrating offshore (e.g., Urophycis tenuis, white hake).

• Marine Stragglers (MS) spawn and complete their entire life cycles further

offshore but occasionally appear in the estuarine environment (e.g., Limanda

ferruginea, yellowtail flounder).

• Estuarine Residents (ER) spawn within the estuary and reside there throughout

ontogeny (e.g., Menidia menidia, Atlantic silverside).

• Estuarine Migrants (EM) spawn in nearshore areas but make extensive use of

marine or freshwater habitats throughout their life cycles (e.g., Gasterosteus

wheatlandi, blackspotted stickleback).

• Freshwater Migrants (FM) spawn in freshwater but frequently migrate into

coastal nearshore areas when conditions are favourable (e.g., Pungitius pungitius,

ninespine stickleback).

• Freshwater Stragglers (FS) spawn and complete their entire life cycles in

freshwater but occasionally appear in nearshore coastal areas (e.g., Notropis

heterolepis, blacknose shiner).

• Diadromous (DA) species which regularly migrate between fresh and salt water,

often residing in one environment while spawning in the other. This guild

includes anadromous (e.g., Osmerus mordax, rainbow smelt), catadromous (e.g.,

Anguilla rostra, American eel) and amphidromous fishes (e.g., Eleotris

acanthopoma, Sleeper).

Vertical Distribution

• Pelagic species (P) which occupy the upper portions of the water column with

little direct dependence upon the substrate (e.g., Clupea harengus, Atlantic

herring).

• Demersal species (D) which are closely associated with the bottom (e.g., Gadus

morhua, Atlantic cod).

Reproductive Type

• Viviparous species (V) produce free-living offspring that develop and obtain

nourishment from within the female’s body (e.g., Embiotocidae).

• Ovoviviparous species (W) produce free-living offspring which hatch from eggs

carried within the parent’s body without obtaining nourishment from the parent

(e.g., Syngnathidae).

• Oviparous species (O) produce eggs which hatch outside the adult’s body and

undergo a larval stage during ontogeny (e.g., Gadidae).

Egg Dispersal

• Pelagic egg producers (P) allow currents to facilitate the dispersal of eggs;

includes semi-demersal/pelagic eggs which drift with the current above the

substrate (e.g., Urophycis tenuis, white hake or Alosa pseudoharengus, alewife).

• Demersal egg producers (D) which deposit eggs on the substrate minimizing

dispersal (e.g., Menidia menidia, Atlantic silverside).

Residency

• Regular species (R) occur in nearshore areas throughout the year (e.g., Menidia

menidia, Atlantic silverside).

• Summer Periodic species (SP) frequent nearshore areas during the warmer

months of the year and are absent during winter (e.g., Urophycis tenuis, white

hake).

• Winter Periodic species (WP) frequent nearshore areas solely during the coldest

months of the year (Liparis atlanticus, Atlantic snail fish).

100

• Occasional species (O) occur rarely in nearshore areas (i.e., less than 10

individuals sampled per site) and seasonal patterns of occurrence can not be

confidently determined based on low catches.

Maturity

• Juvenile (J) includes species which occupy the nearshore environment prior to

reaching sexual maturity (e.g., Urophycis tenuis, white hake).

• Adult (A) includes species which occupy the nearshore environment after

reaching sexual maturity (e.g., Anguilla rostra, American eel).

• Mixed (J/A) includes species which occupy the nearshore environment during

both juvenile and adult life history stages (e.g., Menidia menidia, Atlantic

silverside).

3.4 Results

A total of 56 families and 110 species were observed among 15 nearshore areas in the NWA (Table 3.2). Species richness and the number of families followed a unimodal pattern with respect to latitude as values steadily increased until reaching a peak spanning from the southern edge of Cape Cod (site 9, 41.33°N) to New Jersey (site

11, 39.54°N) and then decreasing toward Cape Hatteras (site 15, 35.13°N, Figure 3.2,

Table 3.2).

101

3.4.1 Taxonomic Analyses

Cluster analyses indicated four main geographic groupings among taxa. At the family level, two groups initially diverged at 31.46% similarity (Figure 3.3). The sites found in each of the two divisions were geographically separated from each other by the zoogeographic boundary at Cape Cod (41.5°N); separating the northern sites (1-8,

Labrador and Acadian provinces) from the southern sites (9-15, Virginian province).

Subsequent diversions in each of these groups identified further geographic separation with sites in the Labrador (site 1) and Acadian (sites 2-8) zoogeographic provinces separating from each other, while in the Virginian province northern sites (9-11) separated from southern sites (12-15, Figure 3.1). These four groups were also evident in the species data (Figure 3.4) with the initial division at 16.79% separating southern sites in the Virginian province (12-15), from more northerly sites (1-11). The northern group subsequently broke down separating into the Labrador (site 1), Acadian (sites 2-8) and northern sites from the Virginian province (sites 9-11, Figure 3.4).

3.4.2 Functional Guild Analyses

Functional guild classifications for each of the 110 species encountered throughout the NWA are presented Table 3.3. In terms of overall guild structure based upon species composition (Table 3.4), NWA nearshore fish assemblages were dominated by marine migrants (MM: 46.4%) followed by estuarine residents (ER:

26.4%). The majority of these fishes were demersal (D: 63.6%) utilizing an oviparous reproductive strategy (O: 95.5%), produced pelagic eggs (P: 57.3%) and occurred either

102 infrequently or only during the warmer months of the year (O: 47.9%, SP: 36.1%) occupying the nearshore area exclusively during the juvenile stages (J: 54.0%). However marked differences were observed with respect to the total catch of fishes occupying these guilds (Table 3.4). In terms of individuals, assemblages were largely dominated by estuarine residents (ER: 88.1%) with marine migrants of less importance (MM: 5.8%).

The majority of individuals were also pelagic (P: 77.0%) despite the prevalence of demersal species. While the oviparous reproductive type still dominated (O: 99.8%), these individuals largely produced demersal eggs (96.1%), and belonged to species which occurred year round (R: 60.0%) in both juvenile and adult stages (J/A: 95.3%).

Several latitudinal gradients were also identified using regression analyses and are examined in detail below. However, with respect to the residency and maturity guilds, information required for classification was insufficient at some sites resulting in smaller sample sizes and subsequent power (residency: n = 9, ß: 0.88 – 0.94, maturity: n = 7, ß:

0.93 – 0.95). As a consequence, negative results should be view critically (Table 3.5).

Ecological Type: The proportion of species exhibiting a diadromous ecological type significantly increased with latitude (r2: 0.546, slope: 0.027, p: 0.002, Table 3.5). These species were largely replaced by marine migrant (MM) and nearshore residents (ER) in southern regions; however significant changes in slope for these variables were not observed (Table 3.5). A similar pattern was also identified with respect to total catch with diadromous individuals dominating the northern latitudes (50-44°N), while declining in the mid and southern latitudes (r2: 0.452, slope: 0.048, p: 0.006), initially being replaced by nearshore residents (ER) in the mid-latitudes (44-38°N) before being

103 replaced by marine migrants (r2: 0.557, slope: -0.055, p: 0.001) in the southern latitudes

(38-34°N, Figure 3.5,). The remaining ecological types occurred in low proportions throughout the 15 nearshore areas examined in the NWA and no significant changes were observed (Figure 3.5, Table 3.5).

Vertical Distribution: No statistically significant relationships were identified with regards to vertical distribution and latitude (Table 3.5). The proportion of pelagic individuals exhibited a general increase with latitude although a statistically significant trend was not observed (r2: 0.224, slope: 0.030, p: 0.075, Figure 3.6).

Reproductive Type: No statistically significant relationships between reproductive type and latitude were identified (Figure 3.7, Table 3.5). Nearshore finfish communities throughout the NWA were consistently dominated by oviparous fishes (>90% of species and individuals per site), while viviparous and ovoviviparous fishes occurred infrequently and in low abundance.

Egg Dispersal: A significant relationship was identified between egg dispersal and latitude (Table 3.5). The proportion species producing demersal eggs significantly increased with latitude (Species r2: 0.881, slope: 0.044, p: <0.001, Abundance r2: 0.624, slope 0.040, p: <0.001) while pelagic egg producers exhibited the opposite trend (Figure

3.6, Table 3.5).

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Residency: The proportion of summer periodic species significantly decreased with increasing latitude (r2: 0.546, slope: -0.013, p: 0.023, Table 3.5, Figure 3.9). However no significant relationships were identified in relation to the remaining residency types.

Only a single winter periodic species was observed (Liparis liparis, site 1).

Maturity: No statistically significant patterns were observed with maturity and latitude

(Table 3.5) however the proportion of species occurring as both juveniles and adults generally increased with latitude while juveniles generally decreased (Figure 3.10).

3.5 Discussion

Taxonomic structure of the 15 nearshore finfish assemblages examined in the

NWA reflected existing biogeographic provinces for coastal biota in the region (Briggs

1974); with detectable differences in taxa among the Labrador, Acadian and Virginian provinces. This supports current hypotheses that Cape Cod (41.5°N) and the Avalon

Peninsula (46.6°N) act as biogeographic boundaries delineating thermal regimes and subsequently dividing taxa based on their physiological tolerances to varying environmental conditions (Briggs 1974, Ayvazian et al. 1992). The influence of these biogeographic boundaries was particularly evident when taxa were examined at the family level, however on top of these established boundaries, an additional division was observed within the Delaware Bay region (38.8°N) of the Virginian province. This division was also apparent when taxa were compared at the species level, with sites south of Delaware Bay showing a low degree of similarity relative to the remaining sites

105 examined. The cause of this is divergence is mostly likely due to the role of the northern portion of the Virginian province as a transitional zone between the Acadian and

Virginian regions. Due to the mixing of cold water from the Labrador Current and warm water from the Gulf Stream in this region suitable conditions are produced for species native to either province. This premise is supported by considerable overlap in species composition observed from both Acadian and Virginian taxa in the region not observed elsewhere.

With respect to functional guild structure NWA nearshore fish assemblages were dominated by marine migrant species (MM: 46.4%) followed by estuarine residents

(ER: 26.4%) similar to previous findings by Ayvazian et al. (1992). The majority of these fishes were demersal (D: 63.6%), utilizing an oviparous reproductive strategy (O:

95.5%) consistent with observations for the Northeast Atlantic (NEA) made by Elliott and DeWailly (1995). The majority of these species produced pelagic eggs (P: 57.3%) and occurred either infrequently or only during the warmer months of the year (O:

47.9%, SP: 36.1%) occupying the nearshore area exclusively during the juvenile stages

(J: 54.0%). However marked differences were observed with respect to the total catch of fishes occupying these guilds similar to findings by Thiel et al. (2003) who compared the proportion of species and the proportion of individuals contributing to various ecological guilds. In terms of individuals, assemblages were largely dominated by estuarine residents (ER: 88.1%) with marine migrants of less importance (MM: 5.8%).

106 which occurred year round (R: 60.0%) in both juvenile and adult stages (J/A: 95.3%).

Several relationships were identified among various species traits and latitude:

Ecological Type: The majority of species encountered in the NWA were diadromous, estuarine residents or marine migrants; however their relative proportions changed with latitude. Diadromous fishes dominated the northern latitudes while estuarine residents dominated the mid latitudes and marine migrants the south. These findings were consistent with previous work on latitudinal variation of ecological guilds by Helfman et al. (1997) and Nordlie (2003). This trend was particularly evident when ecological guilds were examined based on the proportion of individuals occupying these guilds.

Remaining ecological types (MS, EM, FM, and FS) remained in very low proportions and subsequently did not constitute a major component of the nearshore fish assemblage of the NWA.

Vertical Distribution: Significant variation in vertical distribution was not detected in relation to latitude. Although this appears to be true with respect to the number of species, a general decrease in the proportion of demersal individuals with decreasing latitude was observed.

Reproductive Type: Oviparous fishes dominated the nearshore area of the NWA with viviparous and ovoviviparous fishes occurring rarely and in low abundance. Similar patterns were also observed by Elliott and DeWailly (1995) for European estuaries; however it should be noted that viviparous and ovoviviparous fishes have been show to

107 constitute important portions of other nearshore communities, such as the east Pacific

(e.g., Embiotocidae).

Egg Dispersal: The proportion of species and the proportion of individuals producing demersal eggs significantly increased with latitude which may reflect corresponding latitudinal changes in ecological structure. Since diadromous fishes and estuarine resident fishes dominate the northern latitudes and largely spawn within nursery areas

(whether nearshore or freshwater) they produce demersal eggs to limit dispersal, while marine migrant species which dominated the southern latitudes typically spawn pelagic eggs further offshore allowing ocean currents to distribute offspring throughout the intended nursery area.

Residency: Although few significant latitudinal trends were identified with respect to residency type, a significant increase in the proportion of summer periodic species was observed from north to south. This observation was consistent with Tyler’s (1971) previous predictions regarding changing residency types with latitude for coastal fishes of the NWA, however is not consistent with respect to the underlying processes responsible. Tyler’s (1971) hypothesis stated that more southern coastal waters have a greater annual temperature range resulting in less thermally stable environments and hence fewer species can occupy these areas year round. However, unlike the deeper coastal environments Tyler (1971) based his predictions on, temperatures in shallow nearshore areas exhibit less variability, and throughout the study area ranged by 15.0°C at 45°N (site 3) to 16.7°C at 35°N (site 15), exhibiting minimal change with latitude. As

108 a consequence, although the pattern observed fits Tyler’s (1971) prediction, it is not consistent with the mechanisms outlined in his hypothesis and additional factors such as increased competition would have to be responsible for the southern increase in periodic species observed for the nearshore area.

Maturity: Overall nearshore areas throughout the NWA were widely used as nursery areas consistent with previous findings throughout the region (e.g., Lazzari et al. 1999,

Methven et al. 2001, Beck et al. 2003). Although no statistically significant patterns were observed with latitude these analyses were based on a low sample size (n=7) and should be viewed critically. In general the proportion of fishes occurring exclusively in the juvenile stages decreased with latitude. This may indicate a greater reliance of fishes on the nursery function of nearshore areas among southern latitudes. This observation likely reflects the increased proportion of marine migrant fishes throughout these areas which commonly inhabit nearshore areas solely during the juvenile stage, prior to migrating into deeper waters during later life history stages.

The functional guild approach has been proven to be a valuable tool in describing the ecological structure of finfish assembalges (Elliott and DeWailly 1995, Whitfield et al. 1999, Mathieson et al. 2000, Thiel et al. 2003); however its suitability for making large scale comparisons is currently limited by inconsistent terminology as well as inadequate biological information. Due to the inherent flexibility of functional guilds in describing ecological traits (Brown 2004), considerable variation in terminology exists with investigators often using different approaches to describe similar concepts (e.g., ecological type: Ayvazian et al. 1992, Elliott and DeWailly 1995, Whitfield et al. 1999,

109

Nordlie 2003). Due to the fact these approaches are rarely standardized, making comparisons between studies is often impractical without reanalyzing data. These inconsistencies also extend to the functional guild concept itself, as multiple synonyms are currently used throughout ecological research (e.g., ‘species traits’, functional traits’, and ‘ecological guilds’ discussed in Wilson 1999) and as a consequence the existing body of literature is largely unorganized impeding accurate reviews of existing information. In order to facilitate future comparisons the adoption of a standardized approach will be necessary for finfish communities. A second obstacle for large scale analyses regards the quality of data currently available for accurate species classification. As discussed by Elliott and DeWailly (1995) the functional guild approach has a fundamental difficulty given that the biology of even common species has not been thoroughly documented, as a consequence classifications are often based on unconfirmed reports or characteristics of members of the same genus. As a result reliability of species classifications are difficult to assess due to the potential for misclassification and as a consequence designations need to be viewed critically.

Overall nearshore fish community structure of the NWA was consistent with previous observations made for coastal fishes of the region. Biogeographic provinces were analogous to those identified by Briggs (1974) with the exception of the northern portion of the Virginian province which exhibited elevated richness due to its location in a transition area for nearshore fishes. Latitudinal gradients were identified in relation to ecological type, egg dispersal and residency indicating the presence of latitudinal variation in functional guild structure of the NWA, however further research will be required in order to identify the processes responsible for these patterns.

110

3.6 Acknowledgements

I would like to thank my supervisors David Methven and Kelly Munkittrick, for their thoughts and guidance while preparing this chapter. I would also like to thank Jeff

Houlahan and members of my supervisory committee, Allen Curry and Simon

Courtenay for their feedback and additional input regarding the use of functional guilds for marine fish assemblages.

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Table 3.1: Sampling locations and protocols for data used in meta-analysis.

Study Authour/Location Latitude Longitude # of Sampling Sampling Gear No. Sites Period Resolution Type Dimensions (mesh) 1 Methven et al. 2001 47° 38' N 53° 43' W 1 07/1982 - 09/1983 Biweekly 1 Seine 9m x 1.5m (9mm) Canada, NL, Bellevue 07/1989 - 09/1990 2 Methven et al. Unpublished 45° 15' N 66° 01' W 2 11/2002 - 12/2003 Monthly Seine 9m x 1.5m (9mm) Canada, NB, Saint John 3 Chapter 2, Seasonal Data 45° 14' N 66° 05' W 3 08/2003 - 08/2004 Biweekly 1 Seine 9m x 1.5m (9mm) Canada, NB, Saint John 4 Chapter 2, Seasonal Data 45° 06' N 67° 03' W 3 08/2003 - 08/2005 Biweekly1 Seine 9m x 1.5m (9mm) Canada, NB, Passamaquoddy Bay 5 Lazzari et al. 1999 43° 45' N 69° 45' W 2 04/1990 - 12/1994 Biweekly1 Seine 36m x 1.8m (8mm) USA, ME, Kennebec Point Fyke 1.2m (7mm) 6 Ayvazian et al. 1992 43° 19' N 70° 30' W 10 04/1988 - 12/1989 Monthly Seine 15m x 2m (4.8mm) USA, ME, Wells Estuary Trawl 4.9m (4.8mm) 7 Wilbur 2004 42° 35' N 70° 40' W 4 06/1998 - 07/1999 Monthly Seine 15m x 1.2m (4.8mm) USA, MA, Gloucester 8 Able et al. 2002 41° 49' N 69° 56' W 3 08/1985 - 12/1985 Bimonthly2 Seine 7.5m (6mm) USA, MA, Nauset Marsh 9 Ayvazian et al. 1992 41° 33' N 70° 31' W 8 03/1988 - 12/1989 Monthly Seine 15m x 2m (4.8mm) USA, MA, Waquoit Bay Trawl 4.9m (4.8mm) 10 Hillman 1977 41° 18' N 72° 10' W 6 05/1969 - 12/1972 Bimonthly2 Seine 9m x 1.2m (6mm) USA, CN, Long Island Sound 11 Rountree and Able 1992 39° 32' N 74° 17' W 3 04/1988 - 11/1988 Biweekly1 Seine 18 x 1.2m (6.4mm) † USA, NJ, Great Bay 04/1989 - 10/1989 12 Layman 2000 37° 24' N 75° 41' W 1 08/1997 - 10/1998 Biweekly1 Seine 8m x 1.5m (4.8mm) USA, VA, Hog Island 13 Schauss 1977 37° 54' N 76° 05' W 16 02/1973 - 01/1974 Monthly Seine 3m x 1.2m (5mm) USA, VA, Lynnhaven Bay 14 Monteiro-Neto 1990 36° 48' N 75° 56' W 1 07/1973 - 06/1974 Monthly Seine 15.2 x 1.8m (6.4mm) USA, VA, Cape Henry 15 Monteiro-Neto 1990 35° 13' N 75° 31' W 1 07/1973 - 06/1974 Monthly Seine 15.2 x 1.8m (6.4mm) USA, VA, Cape Hatteras † Seine used in conjunction with a weir Biweekly 1: Every two weeks Bimonthly 2: Every two months 111

112

Table 3.2: Species encountered in each of the 15 nearshore areas examined in the Northwest Atlantic. The presence of a species at a particular site is indicated by a black dot.

Family Species Site Number Biogeographic Province 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Labrador Acadian Virginian Achiridae Trinectes maculatus Ammodytidae Ammodytes americanus Anguillidae Anguilla rostrata Atherinopsidae Membras martinica Menidia beryllina Menidia menidia Batrachoididae Opsanus tau Belonidae Scomberesox saurus Strongylura marina Tylosurus acus Carangidae Caranx crysos Caranx hippos Caranx latus Selene vomer Trachinotus carolinus Trachinotus falcatus Trachinotus goodei Chaetodontidae Chaetodon ocellatus Clupeidae Alosa aestivalis Alosa mediocris Alosa pseudoharengus Alosa sapidissima Brevoortia tyrannus Clupea harengus Sardinella aurita Congridae Conger oceanicus Cottidae Myoxocephalus aenaeus Myoxocephalus scorpius Cyclopteridae Cyclopterus lumpus Liparis atlanticus Cynoglossidae Symphurus plagiusa Cyprinidae Notropis bifrenatus 112

113

Table 3.2 (cont’d): Species encountered in each of the 15 nearshore areas examined in the Northwest Atlantic. The presence of a species at a particular site is indicated by a black dot. Family Species Site Number Biogeographic Province 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Labrador Acadian Virginian Cyprinidae Notropis heterolepis Cyprinodontidae Cyprinodon variegatus Diodontidae Chilomycterus schoepfii Elopidae Elops saurus Engraulidae Anchoa hepsetus Anchoa mitchilli Ephippidae Chaetodipterus faber Fistulariidae Fistularia tabacaria Fundulidae Fundulus diaphanus Fundulus heteroclitus Fundulus majalis Lucania parva Gadidae Enchelypous cimbrius Gadus morhua Gadus ogac Microgadus tomcod Pollachius virens Urophycis chuss Urophycis tenuis Gasterosteidae Apeltes quadracus Gasterosteus aculeatus Gasterosteus wheatlandi Pungitius pungitius Gerreidae Eucinostomus argenteus Gobiesocidae Gobiesox strumosus Gobiidae Ctenogobius boleosoma Evorthodus lyricus Gobiosoma bosc Hemiramphidae Hemiramphus brasiliensis Hyporhamphus unifasciatus Hemitripteridae Hemitripterus americanus Labridae Tautoga onitis 113

114

Table 3.2 (cont’d): Species encountered in each of the 15 nearshore areas examined in the Northwest Atlantic. The presence of a species at a particular site is indicated by a black dot. Family Species Site Number Biogeographic Province 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Labrador Acadian Virginian Labridae Tautogolabrus adspersus Lutjanidae Lutjanus griseus Monacanthidae Aluterus schoepfii Stephanolepis hispidus Moronidae Morone americana Mugilidae Mugil cephalus Mugil curema Nomeidae Psenes sp. Ophidiidae Ophidion marginatum Osmeridae Mallotus villosus Osmerus mordax Paralichthyidae Paralichthys dentatus Paralichthys squamilentus Pholidae Pholis gunnellus Pleuronectidae Limanda ferruginea Pleuronectes putnami Pseudopleuronectes americanus Poeciliidae Gambusia affinis Pomatomidae Pomatomus saltatrix Rachycentridae Rachycentron canadum Rajidae Amblyraja radiata Sciaenidae Bairdiella chrysoura Cynoscion nebulosus Cynoscion regalis Leiostomus xanthurus Menticirrhus littoralis Menticirrhus saxatilis Micropogonias undulatus Sciaenops ocellatus Scophthalmidae Scophthalmus aquosus Serranidae Centropristis striata

114

115

116

Table 3.3: Functional guild classification for each species encountered in the 15 nearshore areas examined.

Family Species Functional Guild Types Ecological Vertical Reproductive Egg Residency Maturity Type Distribution Type Dispersal Achiridae Trinectes maculatus ER D O P SP * Ammodytidae Ammodytes americanus ER D O D O, SP J/A Anguillidae Anguilla rostrata DA D O P O , R J, A, J/A Atherinopsidae Membras martinica ER P O D R * Menidia beryllina ER P O D O, SP J/A Menidia menidia ER P O D SP, R J/A Batrachoididae Opsanus tau ER D O D R J/A Belonidae Scomberesox saurus MS P O P * * Strongylura marina EM P O D O, SP J, J/A Tylosurus acus MS P O D * * Carangidae Caranx crysos MM P O P * * Caranx hippos MM P O P O J Caranx latus MM P O P * * Selene vomer MM D O P O J Trachinotus carolinus MM P O P SP * Trachinotus falcatus MM P O P * * Trachinotus goodei MM P O P * * Chaetodontidae Chaetodon ocellatus ER D O P * * Clupeidae Alosa aestivalis DA P O P O, SP J Alosa mediocris DA P O D * J Alosa pseudoharengus DA P O P O, SP J Alosa sapidissima DA P O P O J Brevoortia tyrannus MM P O P SP J, J/A Clupea harengus MM P O D O, SP J Sardinella aurita MM P O P * J Congridae Conger oceanicus MM D O P * J Cottidae Myoxocephalus aenaeus ER D O D O, SP J, J/A Myoxocephalus scorpius MM D O D O, SP J Cyclopteridae Cyclopterus lumpus MM D O D O, SP J Liparis atlanticus EM D O D WP J/A Cynoglossidae Symphurus plagiusa MM D O P SP J Cyprinidae Notropis bifrenatus FS D O D O * 116

117

Table 3.3 (cont’d): Functional guild classification for each species encountered in the 15 nearshore areas examined.

Family Species Functional Guild Types Ecological Vertical Reproductive Egg Residency Maturity Type Distribution Type Dispersal Cyprinidae Notropis heterolepis FS D O D O * Cyprinodontidae Cyprinodon variegatus ER D O D SP, R J/A Diodontidae Chilomycterus schoepfii ER D O P * * Elopidae Elops saurus MM P O P O * Engraulidae Anchoa hepsetus EM P O P O J, A Anchoa mitchilli EM P O P O, SP J, J/A Ephippidae Chaetodipterus faber ER P O P * * Fistulariidae Fistularia tabacaria MM D O P * * Fundulidae Fundulus diaphanus FS D O P O * Fundulus heteroclitus ER D O D O, SP, R J/A Fundulus majalis ER D O D SP, R J/A Lucania parva ER P O D R A Gadidae Enchelypous cimbrius MS D O P O * Gadus morhua MM D O P O, R J Gadus ogac MM D O D R J Microgadus tomcod DA D O D O, SP, R J/A Pollachius virens MM D O P O J Urophycis chuss MS D O P O J Urophycis tenuis MM D O P O, SP J Gasterosteidae Apeltes quadracus EM D O D SP J/A Gasterosteus aculeatus DA P O D O, SP, R J/A Gasterosteus wheatlandi EM P O D O, SP, R J/A Pungitius pungitius FM D O D O, R A Gerreidae Eucinostomus argenteus ER P O P SP J Gobiesocidae Gobiesox strumosus ER D O D O J Gobiidae Ctenogobius boleosoma ER D O D * J/A Evorthodus lyricus ER D O D SP J Gobiosoma bosc ER D O D O, SP A, J/A Hemiramphidae Hemiramphus brasiliensis MM P O P SP * Hyporhamphus unifasciatus EM P O P * * Hemitripteridae Hemitripterus americanus MM D O D O J Labridae Tautoga onitis MM P O P SP J 117

118

Table 3.3 (cont’d): Functional guild classification for each species encountered in the 15 nearshore areas examined.

Family Species Functional Guild Types Ecological Vertical Reproductive Egg Residency Maturity Type Distribution Type Dispersal Labridae Tautogolabrus adspersus MM D O P O, SP J, J/A Lutjanidae Lutjanus griseus MM P O P * J Monacanthidae Aluterus schoepfii MM D O D * * Stephanolepis hispidus MM D O D * J Moronidae Morone americana FM P O D SP * Mugilidae Mugil cephalus MM P O P O, SP J Mugil curema MM P O P SP, R J Nomeidae Psenes sp. MS P O P * * Ophidiidae Ophidion marginatum ER D O P * * Osmeridae Mallotus villosus EM P O D SP J/A Osmerus mordax DA P O D O, SP, R A, J/A Paralichthyidae Paralichthys dentatus MM D O P O J Paralichthys squamilentus MM D O P * * Pholidae Pholis gunnellus ER D O D O, SP J/A Pleuronectidae Limanda ferruginea MS D O P O A Pleuronectes putnami ER D O D O * Pseudopleuronectes americanus MM D O D O, SP, R J, J/A Poeciliidae Gambusia affinis FM D V NA SP J/A Pomatomidae Pomatomus saltatrix MM P O P O J Rachycentridae Rachycentron canadum MM D O P * J Rajidae Amblyraja radiata MS D O D O A Sciaenidae Bairdiella chrysoura MM D O P O J Cynoscion nebulosus ER D O P O J Cynoscion regalis ER D O P * * Leiostomus xanthurus MM D O P SP J Menticirrhus littoralis MM D O D SP * Menticirrhus saxatilis MM D O P SP * Micropogonias undulatus MM D O P O J Sciaenops ocellatus ER D O P O, SP J Scophthalmidae Scophthalmus aquosus MM D O P O J, J/A Serranidae Centropristis striata MM D O P O J/A 118

119

Table 3.3 (cont’d): Functional guild classification for each species encountered in the 15 nearshore areas examined.

Family Species Functional Guild Types Ecological Vertical Reproductive Egg Residency Maturity Type Distribution Type Dispersal Sparidae Stenotomus chrysops MM D O P O * Lagodon rhomboides MM D O P O J Sphyraenidae Sphyraena borealis MM P O P O J Stichaeidae Ulvaria subbifurcata MM D O D O J/A Stromateidae Peprilus triacanthus MM P O P * J/A Syngnathidae Syngnathus floridae ER D W NA * * Syngnathus fuscus ER D W NA O, SP A, J/A Syngnathus louisianae ER D W NA * * Synodontidae Synodus foetens MM D O P O J Tetraodontidae Sphoeroides maculatus ER D O D O, SP J Triakidae Mustelus canis MM D V NA * J Triglidae Prionotus carolinus MM D O P O * Prionotus evolans MM D O P O J/A Prionotus tribulus MM D O P * * Uranoscopidae Astroscopus guttatus EM D O P * * * insufficient data for classification

119

120

Table 3.4: Proportional composition of functional guilds based upon species richness (S) and total catch (Ni) for fishes examined in the NWA. See Methods for explanation of abbreviations.

Functional Guild Types Ecological Vertical Reproductive Egg Residency Maturity Type Distribution Type Dispersal

S Ni S Ni S Ni S Ni S Ni S Ni MM: 0.464 0.058 P: 0.364 0.770 V: 0.018 0.000 P: 0.573 0.037 R: 0.151 0.600 J: 0.540 0.046 MS: 0.064 0.000 D: 0.636 0.230 W: 0.027 0.002 D: 0.382 0.961 SP: 0.361 0.398 A: 0.103 0.001 ER: 0.264 0.881 O: 0.955 0.998 NA: 0.045 0.002 WP: 0.008 0.000 J/A: 0.356 0.953 EM: 0.082 0.024 O: 0.479 0.002 FM: 0.027 0.013 FS: 0.027 0.000 DA: 0.073 0.024 Totals 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000

120

121

Ecological Type MM 15 0.232 -0.019 0.069 0.557 -0.055 0.001 MS 15 0.055 0.002 0.401 0.004 0.000 0.817 ER 15 0.242 -0.012 0.063 0.005 0.005 0.810 EM 15 0.001 0.000 0.899 0.001 -0.001 0.900 FM 15 0.043 0.002 0.457 0.013 0.002 0.690 FS 15 0.006 0.000 0.788 0.011 0.000 0.713 DA 15 0.546 0.027 0.002 0.452 0.048 0.006

Vertical Distribution P 15 0.072 -0.006 0.333 0.224 0.030 0.075 D 15 0.072 0.006 0.333 0.224 -0.030 0.075

Reproductive Type V 15 0.151 -0.001 0.152 0.122 0.000 0.202 W 15 0.014 -0.001 0.671 0.112 -0.002 0.223 O 15 0.076 0.002 0.320 0.166 0.002 0.132

Egg Dispersal P 15 0.881 -0.044 <0.001 0.624 -0.040 <0.001 D 15 0.881 0.044 <0.001 0.624 0.040 <0.001 15 Residency R 9 0.020 0.003 0.714 0.093 0.024 0.425 SP 9 0.546 -0.013 0.023 0.113 -0.026 0.378 WP 9 0.250 0.003 0.171 0.250 0.000 0.171 O 9 0.054 0.007 0.547 0.060 0.002 0.525

Maturity J 7 0.148 -0.014 0.394 0.314 -0.022 0.190 A 7 0.310 0.011 0.195 0.173 0.000 0.354 J/A 7 0.008 0.003 0.852 0.320 0.022 0.186

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Figure 3.1: Location of nearshore studies used in large scale comparison. Biogeographic provinces identified by dashed lines and italics.

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20 Taxonomic Groups

0 50 48 46 44 42 40 38 36 34

Latitude (°N)

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Figure 3.3: Percent similarity of 15 nearshore areas examined in the northwest Atlantic based on family data as indicated by the Bray- Curtis index using a binary matrix. Zoogeographic provinces listed (Briggs 1974). See Table 3.1 for site details. 124

125

Figure 3.4: Percent similarity of 15 nearshore areas examined in the northwest Atlantic based on species data as indicated by the Bray- Curtis index using a binary matrix. Zoogeographic provinces listed (Briggs 1974).See Table 3.1 for site details. 125

126

1.0 MM MS r2: 0.232 2 0.8 r : 0.055

0.6

0.4

0.2

0.0

1.0 ER EM 2 2 0.8 r : 0.242 r : 0.001

0.6

0.4

0.2 Proportion of Species Proportion

0.0

1.0 FM FS 2 r2: 0.006 0.8 r : 0.043

0.6

0.4

0.2

0.0

1.0 50 48 46 44 42 40 38 36 34 DA 2 0.8 r : 0.546

0.6

0.4

0.2

0.0

50 48 46 44 42 40 38 36 34 Latitude (°N)

Figure 3.5: Proportion of species and individuals exhibiting specific ecological types across latitude. See text for guild definitions.

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1.0 MM MS r2: 0.899 2 0.8 r : 0.004

0.6

0.4

0.2

0.0

1.0 ER EM 2 2 0.8 r : 0.941 r : 0.001

0.6

0.4

0.2 Proportion of Proportion Individuals 0.0

1.0 FM r2: 0.013 FS 0.8 r2: 0.011

0.6

0.4

0.2

0.0

1.0 50 48 46 44 42 40 38 36 34 DA 2 0.8 r : 0.916

0.6

0.4

0.2

0.0

50 48 46 44 42 40 38 36 34 Latitude (°N)

Figure 3.5 (cont’d): Proportion of species and individuals exhibiting specific ecological types across latitude. See text for guild definitions.

128

1.0 P D D 2 r2: 0.072 0.8 r : 0.072

0.6

0.4

0.2 Proportion of Species

0.0

1.0 P D 2 2 0.8 r : 0.224 r : 0.224

0.6

0.4

0.2 Proportion of Individuals 0.0

50 48 46 44 42 40 38 36 34 50 48 46 44 42 40 38 36 34 Latitude (°N)

Figure 3.6: Proportion of species and individuals exhibiting pelagic (P) or demersal (D) vertical distributions across latitude. See text for guild definitions.

129

1.0 V W r2: 0.151 r2: 0.014 0.8

0.6

0.4

0.2

0.0

1.0 50 48 46 44 42 40 38 36 34 O 0.8 2 Proportion of Species Proportion r : 0.076

0.6

0.4

0.2

0.0

1.0 V W 2 r2: 0.122 r : 0.112 0.8

0.6

0.4

0.2

0.0

1.0 50 48 46 44 42 40 38 36 34 O 2 0.8 r : 0.166

Proportion of Individuals Proportion 0.6

0.4

0.2

0.0

50 48 46 44 42 40 38 36 34 Latitude (°N)

Figure 3.7: Proportion of species and individuals exhibiting viviparous (V), ovoviviparous (W) and oviparous (O) reproductive types across latitude. See text for guild definitions.

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1.0 P D r2: 0.881 2 0.8 r : 0.881

0.6

0.4

0.2 Proportion of Species

0.0

1.0 P D 2 r2: 0.990 0.8 r : 0.851

0.6

0.4

0.2 Proportion of Individuals 0.0

50 48 46 44 42 40 38 36 34 50 48 46 44 42 40 38 36 34 Latitude (°N)

Figure 3.8: Proportion of species and individuals exhibiting pelagic (P) or demersal (D) egg dispersals across latitude. See text for guild definitions.

131

1.0 R SP r2: 0.020 r2: 0.546 0.8

0.6

0.4

0.2

0.0

1.0 WP O 2 r2: 0.054 0.8 r : 0.250 Proportion of Species 0.6

0.4

0.2

0.0

1.0 R SP r2: 0.093 r2: 0.113 0.8

0.6

0.4

0.2

0.0

1.0 WP O 2 r2: 0.060 0.8 r : 0.250

Proportion of Individuals 0.6

0.4

0.2

0.0

50 48 46 44 42 40 38 36 34 50 48 46 44 42 40 38 36 34 Latitude (°N)

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1.0 J A r2: 0.148 2 0.8 r : 0.310

0.6

0.4

0.2

0.0

1.0 50 48 46 44 42 40 38 36 34 J/A 2 0.8 r : 0.008 Proportion of Species 0.6

0.4

0.2

0.0

1.0 J A 2 2 0.8 r : 0.314 r : 0.173

0.6

0.4

0.2

0.0

1.0 50 48 46 44 42 40 38 36 34 J/A 2 0.8 r : 0.320 Proportion of Individuals Proportion 0.6

0.4

0.2

0.0

50 48 46 44 42 40 38 36 34 Latitude (°N)

Figure 3.10: Proportion of species and individuals exhibiting juvenile (J), adult (A) and mixed (J/A) maturity types across latitude. See text for guild definitions.

133

3.7 Literature Cited

Ayvazian, S.G., L.A. Deegan, and J.T. Finn. 1992. Comparison of habitat use by estuarine fish assemblages in the Acadian and Virginian provinces. Estuaries. 15(3): 368-383.

Bishop, J.A., and W.L. Myers. 2005. Associations between avian functional guild response and regional landscape properties for conservation planning. Ecological Indicators. 5: 33-48.

Bray, J.R. and J.T. Curtis. 1957. An ordination of the upland forest communities of southern Wisconsin. Ecological Monographs. 27: 325-349.

Briggs, J.C. 1974. Marine Zoogeography. McGrawHill, New York. 475 pp.

Brown, C.S., 2004. Are Functional Guilds More Realistic Management Units Than Individual Species for Restoration? Weed Technology. 18: 1566–1571.

Elliot, M., and F. DeWailly. 1995. The structure and components of European estuarine fish assemblages. Netherlands Journal of Aquatic Ecology. 29(3-4): 397-417.

Elliott, M., and K.L. Hemingway. 2002. Fishes in Estuaries. Blackwell Science. Oxford, UK. 636 pp.

Field, J.G., K.R. Clarke, and R.M. Warwick. 1982. A practical strategy for analyzing multispecies distribution patterns. Marine Ecology Progress Series. 8: 37-52.

Haedrich, R.L. 1983. Estuarine Fishes. In Estuaries and Enclosed Seas. Ecosystems of the World 26 (Ketchum, B.H., ed.). Elsevier Scientific, New York. pp. 183-207.

134

Helfman, G.S., B.B., Collette, and D.E. Facey. 1997. The Diversity of Fishes. Blackwell Science Inc., Malden, USA. 528p.

Hoss, D.E., and G.W. Thayer. 1993. The importance of habitat to the early life history of estuarine dependent fishes. American Fisheries Society Symposium. 14: 147-158.

Layman, C.A. 2000. Fish assemblage structure of the shallow ocean surf-zone on the eastern shore of Virginia barrier islands. Estuarine, Coastal and Shelf Science. 51: 201-213.

McHugh, J.L. 1967. Estuarine nekton. In Estuaries. (Lauff, G.H. ed.). American Association For the Advancement of Science, Washington, DC. 83: 581-620.

Methven, D.A., R.L. Haedrich, and G.A. Rose. 2001. The fish assemblage of a Newfoundland estuary: Diel, monthly and annual variation. Estuarine, Coastal and Shelf Sciences. 52: 669-687.

Methven, D.A., L. Peters and C.J. Arens. Unpublished. Structure of the nearshore fish structure in the lower Bay of Fundy. unpublished manuscript.

O’Connell, T.J., L.E. Jackson, and R.P. Brooks. 2000. Bird guilds as indicators of ecological condition in the Central Appalachians. Ecological Applications. 10: 1706-1721.

Reich, P. B., D. Tilman, and J. Craine. 2003. Do species and functional groups differ in acquisition and use of C, N and water under varying atmospheric CO2 and N

135

availability regimes? A field test with 16 grassland species. New Phytol. 150:435– 448.

Root, R.B. 1967. The niche exploitation pattern of the blue-gray gnatcatcher. Ecological Monographs. 37: 317-350.

Rountree, R.A., and K.W. Able. 1992. Fauna of polyhaline subtidal marsh creeks in southern New Jersey: Composition, abundance and biomass. Estuaries. 15: 171- 185.

Schauss, R.P. 1977. Seasonal occurrence of some larval and juvenile fishes in Lynnhaven Bay, Virginia. The American Midland Naturalist. 98: 275-282.

Shugart, H. H. 1997. Plant and ecosystem functional types. In T. M. Smith, H. H. Shugart, and F. I. Woodward, eds. Plant Functional Types: Their Relevance to Ecosystem Properties and Global Change. Cambridge, UK: Cambridge University Press. pp 20–43.

Szaro, R.C. 1986. Guild management: an evaluation of avian guilds as a predictive tool. Environmental Management. 10: 681-688.

Tyler, A.V. 1971. Periodic and resident components in communities of Atlantic fishes. Journal of the Fisheries Research Board of Canada. 28: 935-946.

Whitfield, A.K. 1999. Ichthyofaunal assemblages in estuaries: A South African case study. Reviews in Fish Biology and Fisheries. 9: 151-186.

Wilbur, A.R. 2004. The relative abundance, distribution, composition, and life history characteristics of fishes in Gloucester Harbour. In; Gloucester Harbour Characterization: Environmental History, Human Influences, and Status of Marine Resources. Massachusetts Office of Coastal Zone Management, pp 41–71.

Wilson, J.B. 1999. Guilds, functional types and ecological groups. Oikos. 86: 507-522.

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4 CHAPTER 4: GENERAL SUMMARY AND CONCLUSIONS

137

4.1 Summary

There were two main objectives to this investigation. The first objective was to assess temporal and spatial variation in the nearshore fish assemblage structure of an under-described portion of the Canadian Atlantic; the southwest Bay of Fundy. The second objective was to use this data in conjunction with existing nearshore records from throughout the NWA and conduct a meta-analysis in order to identify prevailing trends in taxonomic and functional guild structure over a large geographic area;

Newfoundland (47° 38' N) to Cape Hatteras (35° 13' N).

4.1.1 Southwest Bay of Fundy Nearshore Fish Assemblage

Four aspects of assemblage structure were examined in the southwest Bay of

Fundy: a) temporal variability at seasonal and b) tidal/diel scales; c) spatial variability throughout the region and; d) the identification of prevalent ecological characteristics through the use of functional guilds. Significant sources of spatial and temporal variation were identified in the fish assemblage structure of the southwest Bay of Fundy at each of the seasonal, tidal/diel and regional scales examined. At a seasonal scale the assemblage consisted of 18 species and exhibited a high degree of dominance. Seven species accounted for 96.18% of the total catch with M. menidia comprising 53.95%, O. mordax

18.70%, C. harengus 9.25%, P. americanus 3.86%, M. tomcod 3.86%, M. scorpius

3.30%, and G. wheatlandi 3.26%. This degree of dominance appears to be typical of the region and comparable patterns were also observed in the Gulf of Maine by Ayvazian et al. (1992), Lazzari et al. (1999), Able et al. (2002), and Wilbur (2004). Most species occurring in the assemblage were demersal fishes of marine origin and were derived

138 from pelagic eggs. These fishes primarily utilized the nearshore area periodically throughout the warmer months of the year (May – December), largely as a nursery ground.

At the scale of months species richness and abundance were strongly correlated with water temperature but not salinity, exhibiting highs from June through October (S >

8, Ni > 400) and lows December through April (S < 4, Ni < 200). These observations are typical of temperate fish assemblages and are consistent with previous findings on seasonal variation conducted by Lazzari et al. (1999), Methven et al. (2001) and Able et al. (2002) throughout the northwest Atlantic.

Considerable variation in assemblage structure was also observed at a 24 hour scale as species richness and abundance were largely influenced by the tide and time of day. The greatest values for species richness and abundance were observed during low tide, while peaks in abundance occurred at twilight. These results were comparable to previous studies which examined 24 hour variability of nearshore fish assemblages in

Scotland (Gibson et al. 1996) and South Africa (Lasiak 1984).

Spatial variability at the scale of sites within the southwest Bay of Fundy assemblage was largely influenced by substrate type with more structurally complex substrates such as gravel and rock supporting assemblages with greater species richness and abundance than soft substrates such as sand and mud. However spatial proximity among sites had little direct influence on the assemblage structure observed. Habitat type was also identified as the driving factor influencing assemblage composition by Lazzari and Tupper (2001) in the Gulf of Maine.

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Overall, variation in the nearshore fish assemblage of the southwest Bay of

Fundy was influenced by several physical and biological factors operating at multiple spatial and temporal scales. These processes have direct implications for the management of nearshore regions and must be considered when designing sampling protocols for monitoring finfish in order to minimize natural variation in assemblage structure as well as adequately assess patterns and processes responsible for finfish variance.

4.1.2 Northwest Atlantic

The taxonomic structure of the nearshore fish assemblage in the NWA was consistent with previous observations made for coastal fishes of the region. Findings supported the biogeographic provinces proposed by Briggs (1974, Labrador, Acadian,

Virginian) with the exception of the northern portion of the Virginian province which exhibited elevated richness due to its location in a transition area for nearshore fishes, subsequently supporting species from each of the Acadian and Virginian provinces.

With respect to functional guild structure, NWA nearshore fish assemblages supported unique guild structures depending on whether the proportion of species or their relative abundance was examined. In terms of species composition the NWA assemblage was largely dominated by marine migrants (MM: 46.4%). The majority of these fishes were demersal (D: 63.6%), utilized an oviparous reproductive strategy

(95.5%) and produced pelagic eggs (P: 57.3%). These species occurred either infrequently throughout the year or were limited to the warmer months (O: 47.9%, SP:

140

36.1%, May through December), occupying the nearshore area exclusively during the juvenile stages (J: 54.0%).

Marked differences in guild structure were observed when this data was analyzed to incorporate the relative abundance of each species. From this perspective the nearshore assemblages were dominated by estuarine resident fishes (ER: 88.1%). The majority of these individuals were also pelagic (77.0%) despite the overall prevalence of demersal species. Also, while the oviparous reproductive type remained dominant (O:

99.8%), the majority of these individuals produced demersal eggs (D: 96.1%) and were represented by members of both the juvenile and adult life history stages (95.3%).

Latitudinal gradients were also evident over the range of studies examined (47°

38' N through 35° 13' N) with diadromous species being dominant in the northern assemblages and marine migrant species dominating in southern areas. A progressive change in egg dispersal was also observed with demersal eggs being replaced by pelagic eggs from north to south. However further research will be required in order to identify the processes responsible for these trends.

4.2 Conclusions

4.2.1 Functional Guilds

The functional guild approach has been proven to be a valuable tool for describing the ecological structure of finfish assemblages (Elliott and DeWailly 1995,

Whitfield et al. 1999, Mathieson et al. 2000, Thiel et al. 2003). However the suitability of the functional guild approach for making large scale comparisons is currently limited

141 by inconsistent terminology among studies as well as inadequate biological information for many species. Due to the inherent flexibility of functional guilds in describing ecological traits (Brown 2004), considerable variation in terminology exists with investigators often using different approaches to describe similar concepts (e.g., ecological type: Ayvazian et al. 1992, Elliott and DeWailly 1995, Whitfield et al. 1999,

Nordlie 2003). Due to the fact these approaches are rarely standardized, comparisons between studies is often impractical without reanalyzing data.

These inconsistencies also extend to the functional guild concept itself, as multiple synonyms are currently used throughout ecological research (e.g., ‘species traits’, functional traits’, and ‘ecological guilds’ discussed in Wilson 1999) and as a consequence the existing body of literature is largely unorganized impeding accurate reviews of existing information. In order to facilitate future comparisons the adoption of a standardized approach will be necessary for finfish (Whitfield et al. 1999, Elliott

2002).

A second obstacle for large scale analyses regards the quality of data currently available for accurate species classification. As discussed by Elliott and DeWailly

(1995) the functional guild approach has a fundamental difficulty given that the biology of even common species has not been thoroughly documented, and as a consequence classifications are at times based on assumptions, unconfirmed reports or characteristics of closely related species. As a result reliability of species classifications are difficult to assess due to potential misclassification and as a consequence species designations must be viewed critically throughout the functional guild literature.

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4.2.2 Implications for Management of Nearshore Areas

Physical and biological processes operating at multiple spatial and temporal scales introduce natural variability into an ecosystem and have considerable influence on the fish assemblage structure observed in nearshore environments. As a consequence, it is important to consider spatiotemporal variation when designing sampling protocols for monitoring these species. Otherwise natural processes may introduce sources of variation which confound accurate interpretation of the results. Based on the findings of this study the optimal time and place to sample in the southwest Bay of Fundy while maintaining the highest levels of richness and abundance is to sample at sites with complex substrates (e.g., gravel, algal coverage), at low tide, throughout the warmest months of the year (May – December). Sampling during alternate periods may underestimate the species richness and abundance of the fish assemblage (Stoner 1991).

4.2.3 Future Research

As monitoring of finfish assemblages continues to become an integral part of environmental and fisheries research, further study will be required to determine how marine nearshore fish assemblages are influenced by anthropogenic effects as well as identifying patterns and processes responsible for temporal variation at scales of decades and centuries.

The effects of contaminants on fish assemblage structure and ecosystem health has received considerable attention in freshwater ecosystems (Munkittrick 2000); however comparably little information exists regarding how these factor alter estuarine and marine assemblages. Current research in marine environments has largely focused

143 on natural processes known to influence fish community structure such as temperature and salinity (e.g., Haedrich 1983, Methven et al. 2001). Meanwhile our understanding of the influence factors such as toxic substances, oxygen content and light intensity have on community structure remains limited despite the considerable influence these parameters potentially have on the value of specific habitats to fishes (Ryder and Kerr 1989, Peters and Cross 1992).

A second area of interest for future research will be identifying the processes responsible for natural variability in nearshore finfish communities over large temporal scales. Due to the fact humans perceive time on a diel to annual time frame, research often lacks perspective beyond these scales. As a consequence nearshore research to date has largely focused on spatiotemporal variability throughout the course of one or two years. However evidence has shown that these communities operate in response to processes operating at scales of decades to centuries where the number of standardized data sets available is greatly reduced. In order to detect long term changes in assemblage structure future research will require a long-term perspective which will permit delineation between natural and anthropogenic induced changes (Lekve et al. 1999).

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4.3 Literature Cited