MOVEMENT PATTERNS AND TROPHIC STRUCTURE OF A RESERVOIR FISH COMMUNITY ASSESSED USING STABLE ISOTOPE ANALYSIS by Jonathan Adam Freedman
Bachelor of Science, University of Guelph, 2001
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
Master of Science
In the Graduate Academic Unit of Biology
Supervisors: Allen Curry, Ph.D., Canadian Rivers Institute, Biology Department, UNB Fredericton Kelly Munkittrick, Ph.D., Canadian Rivers Institute, Biology Department, UNB Saint John
Examining Board: Karen A. Kidd, Ph.D., Biology Department, UNB Saint John, Chair Will C. van den Hoonaard, Ph.D., Department of Sociology, UNB Fredericton
This thesis is accepted by the Dean of Graduate Studies
THE UNIVERSITY OF NEW BRUNSWICK
September, 2005
© Jonathan A. Freedman, 2005
ABSTRACT
Pulp mill and municipal sewage effluents can affect fishes in many ways and environmental monitoring programs, often using a sentinel-species approach, have been developed to assess these effects. With applications to environmental monitoring studies in mind, the goals of my thesis were to use stable isotope analysis to determine fish community structure in the presence of pulp mill and sewage treatment plant effluents, and to assess the movements and site-fidelity of common fish species in this area of Mactaquac Lake at
Nackawic, New Brunswick. My results indicate that pulp mill- and sewage effluent-exposed sites have lower species richness, abundance, and diversity.
Fishes that are present show marked differences in trophic position and dietary
sources than those at non-exposed reference sites. Yellow perch and white sucker showed high site-fidelity while white perch showed high inter-site movements. Brown bullhead and banded killifish showed intermediate or uncertain degrees of movement. These results suggest that the pulp mill effluent and municipal wastewater effluent do affect the fish communities, while yellow perch and white sucker would make the best sentinel species. The use of local reference sites is also supported for future studies at the pulp mill in Nackawic.
ii ACKNOWLEDGMENTS
I would like to thank my parents for their ongoing support (both moral and financial) of my continuing academic endeavours. They’ve always believed in me, and I know that I wouldn’t be where I am today without them.
None of this research could have happened without the field and lab assistance of many people; I would like to thank Alexa Alexander, Eric Chernoff,
Marcia Chiasson, Chad Doherty, Mark Gautreau, Kristie Heard, Emily Kitts,
Olivia Logan, Jenny Reid, Kirk Roach, Jennifer Shaw, and Karma Tenzin, all of whom went well above and beyond the call of duty. You’re all a part of this thesis, and I can’t thank you enough for all of your help.
Tim Jardine, Anne McGeachy, Christine Patten, and Mireille Savoie of the
Stable Isotopes in Nature lab provided invaluable expertise and advice.
All of the students and staff of the Biology Department and the Canadian
Rivers Institute who together have made this an excellent and enjoyable experience for me.
The denizens of Bailey Hall room 229, for much needed advice and commiserations, and for (almost) always taking me with a grain of salt and suffering my occasional foolishness gladly; especially Sherisse McWilliam-
Hughes who sat next to me for two years with nary a word of complaint, but a willing and excellent source of advice and suggestions.
The Behavioural Ecology and Evolution Research Society which sated my thirst every Friday, and provided untold (and occasionally unremembered) inspiration. Calix meus inebrians.
iii I would like to thank my committee members Dr. Joseph Culp, Mr. Roy
Parker, and Ms. Eileen Blair. Roy and Joseph for their support, for bringing
Environment Canada expertise to the table, and for years of EEM experience, and Eileen for bringing her knowledge of the industry and for bringing funding to the table from the mill.
Finally, I would like to thank my supervisors, Drs. Allen Curry and Kelly
Munkittrick, whose support and input throughout this project was always excellent, if not always timely. I’ve learned a lot from you, and I really appreciate all that you’ve done for me.
iv TABLE OF CONTENTS
ABSTRACT ...... ii
ACKNOWLEDGMENTS ...... iii
TABLE OF CONTENTS ...... v
LIST OF TABLES ...... viii
LIST OF FIGURES ...... ix
1 General Introduction ...... 1
1.1 Motivation and Rationale for Project ...... 1
1.2 Description of Study Site ...... 2
1.3 Why Study Fish Communities and Movements? ...... 3
1.3.1 Methods for Studying Fish Communities and Movements...... 5
1.4 Stable Isotope Analysis ...... 6
1.4.1 Stable Isotope Baselines ...... 8
1.4.2 Selecting Stable Isotopes and Tissues ...... 9
1.5 Objectives...... 12
1.6 Literature Cited ...... 13
2 Fish assemblages and trophic structure in a temperate reservoir
receiving anthropogenic inputs ...... 22
2.1 Abstract ...... 22
2.2 Introduction...... 23
2.3 Methods...... 26
2.3.1 Study Site ...... 26
2.3.2 Fish Community Sampling...... 27
v 2.3.3 Stable Isotope Analysis ...... 28
2.3.4 Data Analysis...... 30
2.4 Results...... 32
2.4.1 Community Analysis ...... 32
2.4.2 Stable Isotope Analysis ...... 33
2.5 Discussion ...... 36
2.5.1 Fish Communities ...... 36
2.5.2 How are stable isotope signatures affected by PME?...... 39
2.5.3 Conclusions and Integration ...... 45
2.6 Literature Cited ...... 48
3 Tracking movement patterns and site fidelity of fishes in a
temperate reservoir using stable isotopes ...... 73
3.1 Abstract ...... 73
3.2 Introduction...... 74
3.3 Methods...... 76
3.3.1 Study Site ...... 76
3.3.2 Fish Sampling ...... 77
3.3.3 Stable Isotope Sample Preparation ...... 78
3.3.4 Data Analysis...... 80
3.4 Results...... 80
3.4.1 How Much do the Fishes Move?...... 80
3.4.2 Is Fish Condition Affected Near the PME Discharge? ...... 82
3.5 Discussion ...... 82
vi 3.5.1 How much do the fish move?...... 82
3.5.2 Are the fish affected by PME? ...... 86
3.5.3 Conclusions ...... 87
3.6 Literature Cited ...... 89
4 General Discussion...... 106
4.1 Integration and Applications of Findings ...... 107
4.2 Applications to environmental monitoring studies...... 109
4.3 Conclusions and Suggestions for Future Research...... 111
4.4 Literature Cited ...... 113
Curriculum Vitae
vii LIST OF TABLES
Table 1. Total numbers of fish species caught at 12 sites in Mactaquac Lake, NB, giving common name, scientific name, and abbreviated name for each species...... 54 Table 2. Mean proportion of reliance on littoral resources (“Litt.,” from δ13C analysis) and mean trophic position (“T.P.,” from δ15N analysis) for fish species from 12 sites in Mactaquac Lake, NB. Species abbreviations are as described in Table 1, while the suffixes “sm,” “med,” and “lg” denote small (<15cm fork-length for WS, <10cm for other species), medium (10-18cm for WP, 10-16cm for YP), and large (>10 cm for CS, FF, GS and PSS, >15cm for WS, >18cm for WP, and >16cm for YP) sized fish, respectively...... 57 Table 3. Fish community and stable isotope sampling sites, with site name, abbreviation, and location...... 95 Table 4. Percentage of each species classified to each site type using discriminant analysis. Bold denotes the percentage correctly assigned...... 96 Table 5: Comparison of Environmental Effects Monitoring endpoints in white sucker (Catostomus commersoni) and yellow perch (Perca flavescens) from the Cycle 3 Adult Fish Survey at Nackawic, Mactaquac Lake, NB…………………………………………………..112
viii LIST OF FIGURES
Figure 1: Map of the study sites in Mactaquac Lake, NB. Solid circles with captions “PME” and “STP” denote pulp mill and sewage treatment plant effluent outfalls, respectively...... 21 Figure 2: Map of study sites in Mactaquac Lake, NB. US: upstream sites, DS: downstream sites, FB: far-bank sites, STP: sewage treatment plant discharge site, NS: Nackawic stream site. Solid circles with captions “PME” and “STP” denote pulp mill and sewage treatment plant effluent outfalls, respectively...... 63 Figure 3: Total Catch (# individuals caught per site), Species Richness (# species caught per site), and Shannon-Wiener Diversity (H’loge) of fish caught at 12 sites in Mactaquac Lake, NB. Total pooled values are given, as are those for different capture techniques: gill-nets, trap-nets, and beach seines. Trap nets were not used at FB1 or STP, and seines were not used at FB1...... 64 Figure 4: Whittaker plot of species rank abundance and total catch of fish caught in Mactaquac Lake, NB...... 65 Figure 5: Relative proportion of catch for 5 common fish species at 12 sites in Mactaquac Lake, NB. All other species are grouped into the “Other Species” category...... 66 Figure 6: Line graphs of mean δ13C and δ15N (± SE) for baselines (mussels and snails) and five common fish species from sites in Mactaquac Lake, NB...... 67 Figure 7: Bivariate plots of δ13C and δ15N for fish assemblages at 12 sites in Mactaquac Lake, NB. Error bars indicate ± SE; fish species abbreviations are given in Table 1; “Sn” indicates snails and “Ms” indicates mussels; and the suffixes “sm,” “med,” and “lg” denote small-(<15cm fork-length for WS, <10cm for other species), medium- (10-18cm for WP, 10-16cm for YP), and large- (>10 cm for CS, FF, GS and PSS, >15cm for WS, >18cm for WP, and >16cm for YP) sized fishes, respectively. Symbols indicate feeding group (□ – baseline, ● – benthic invertivore, ○ – pelagic invertivore, ▲ – piscivore)...... 70 Figure 8: Map of study sites in Mactaquac Lake, NB. US: upstream sites, DS: downstream sites, FB: far-bank sites. Solid circle with caption “PME” denotes pulp mill effluent outfall………………………………………….97 Figure 9: Line graphs of mean δ13C and δ15N (± SE) for baselines (mussels and snails) and five common fish species from sites in Mactaquac Lake, NB...... 98 Figure 10: Scatter plots of stable isotope data, with ELM bivariate ellipses (solid line – DS sites, dashed – FB, dotted – US) for data points grouped according to site type for (a) banded killifish, (b) brown bullhead, (c) white sucker, (d) white perch, and (e) yellow perch. ELM bivariate ellipses represent an estimate of the standard error of the mean for all data points of that type...... 101
ix Figure 11: Fulton’s condition factor (K) for five common fish species in Mactaquac Lake, NB……………………………………………………..105
x 1 GENERAL INTRODUCTION
1.1 Motivation and Rationale for Project
The Canadian Environmental Effects Monitoring (EEM) program was instituted under the Fisheries Act in 1992 to test whether pulp and paper mills were associated with impacts in their receiving environments, when the effluent is otherwise in compliance with existing regulations. Pulp and paper mills are required to have full environmental monitoring programs every three years, which include studies on fishes and benthic invertebrates. Samples of two sentinel fish species are taken from the receiving environment, and assessed for reproductive fitness, stress, and overall condition in comparison to fish caught at an undisturbed/unexposed (reference) site. Differences among the parameters between the exposure and reference sites indicate environmental effects of the effluent on the fishes. To ensure exposure to effluent, ideal sentinel species for
EEM are benthic (bottom-dwelling) feeders, and show home-range fidelity and limited movement patterns (Munkittrick et al. 2000).
The Saint John River flows over 600 km from its headwaters in northern
Maine to the Bay of Fundy. The river is restricted by a number of hydroelectric dams, and receives effluents from numerous pulp and paper mills, food processing plants and sewage outfalls (Curry and Munkittrick 2005). A series of studies on the impacts of effluents on fish populations has been underway since
1999, working progressively downstream (Galloway et al. 2003; Gray et al. 2004;
Curry and Munkittrick 2005; Doherty et al. 2005).
1 The river reach near Nackawic, New Brunswick, receives effluent from a
large pulp mill, and is influenced to varying degrees by both upstream and
downstream hydroelectric facilities. In the first cycle of EEM studies at the St.
Anne-Nackawic Pulp Mill (in 1995) yellow perch (Perca flavescens) and white
sucker (Catostomus commersoni) were used as the sentinel species (BEAK
1996), while the Cycle 2 study (in 1999) assessed only yellow perch (BEAK
2000). The reference site for the adult fish survey for the EEM cycles 1 and 2 at
the Nackawic pulp mill was the Beechwood reservoir, located approximately 120
km upstream from Nackawic (Beak 1996, 2000). Due to concerns that differing
habitat and environmental variables and fish community composition rendered
Beechwood an inappropriate reference site, two alternative reference sites were
identified for the Cycle 3 survey – Meductic about 15 km upstream, and the lower
arm of Mactaquac Lake, about 40 km downstream from Nackawic (Stantec
2004). In the long-term, however, it was decided to identify local reference sites
– located in close geographic proximity to the exposure area but effectively
isolated in terms of fish movements. To better differentiate PME-mediated
effects from background effects, a fish community survey would also be
undertaken to help understand the trophic structure of the fish community in
Mactaquac Lake.
1.2 Description of Study Site
The Saint John River watershed encompasses approximately 55 100 km2 of New Brunswick, Quebec, and Maine. Mactaquac Lake is an impoundment of
2 the Saint John River formed by the construction of the Mactaquac hydroelectric
dam in 1968, and the impoundment extends 104 km upstream to Woodstock,
encompassing an area of 8 350 ha. Mactaquac dam is located approximately 85
km upstream of the mouth of the Saint John River, and 13 km upstream of
Fredericton. Located at a bend in the lacustrine reach, approximately 37 km upstream of the dam, are the town of Nackawic and its associated pulp mill
(Figure 1).
The pulp mill at Nackawic was a bleached kraft hardwood mill which made pulp for use in photographic paper. The mill’s output averaged approximately
719 air-dried tonnes per day from 1996-2003, and over the same time discharged approximately 65 000 m3 of waste water per day into the receiving environment (Stantec 2004). The mill’s effluent underwent primary
(desedimentation) and secondary (aeration) treatment over an average of 17
days before being discharged into the receiving environment by a multi-port
diffuser located approximately 175 m offshore (Stantec 2004). The mill shut
down indefinitely in the autumn of 2004, after all sampling for this project had
been completed.
1.3 Why Study Fish Communities and Movements?
The community is one of the fundamental units of organization for organisms. A community comprises a series of populations each of which is made up of individuals from separate species. Groups of communities, together with their respective environments, in turn, comprise an ecosystem. A food web
3 describes species interactions such as predator-prey-competitor relationships,
and is effectively an interconnected series of food chains. As such, food webs
can indicate energy and nutrient transfers within a community, and comprise an
integral part of community ecology.
Movements of fishes, and of other animals, are a fundamental part of their
ecology. Fish movements can take place on a scale of anywhere from a few
millimetres to thousands of kilometres, for feeding or breeding, and largely
depend on the size and other life history characteristics of the individual species
(Bond 1996). The factors influencing these movements can be biotic or abiotic,
intrinsic or extrinsic and, as with communities, can often confound one another.
Fish community structure is influenced by both biotic factors such as
biogeography, prey-availability, and niche-availability; and abiotic factors such as
habitat, temperature, water velocity, turbidity, and depth. Anthropogenic impacts
can influence community structure, generally by affecting the factors listed
above. Dams and other obstructions can prevent fish movement. Local
populations of anadromous species can be extirpated if they are unable to migrate to reproduce. Over-fishing of certain species, such as apex predators, can have a trickle-down effect on the fish community (de Bruyn et al. 2004,
Vander Zanden et al. 1999). As predation or competitive pressure is relieved, some species can thrive and overwhelm other species (de Bruyn et al. 2004).
Likewise, the introduction of non-native species can have severe repercussions on the native biotic community, either by preying on native species, or by competitive exclusion (Vander Zanden et al. 1999).
4
1.3.1 Methods for Studying Fish Communities and Movements
Species richness is a count of the total number of species, and is commonly
used in basic management practices. However, it does not take into account
abundance of these species or whether they are endemic or exotic, etc (Krebs
1999). Total abundance is the total number of individuals at a site, while relative
abundance is the number of individuals in samples compared to other samples.
Species richness and abundance, when used together, can be used to calculate a variety of indices. Species diversity, evenness, and heterogeneity all provide similar information, namely how diverse the community is and how much it may be dominated by certain species (Krebs 1999).
Lucas and Baras (2000) reviewed many of the techniques which can be
used to study the spatial behaviour of fishes. They subdivided these into
capture-independent and capture-dependent methods. Capture-independent
methods include: visually observing fishes (such as at fishways, or while diving),
and hydroacoustic techniques (such as “fish-finders”). Capture-dependant
methods include: relative measures of catch-per-unit-effort (CPUE) which can
either result from active research sampling or creel-type commercial surveys; use
of natural marks, and mark-recapture studies (Skinner 2005); radio- and sonic-
telemetry; and passive integrated transponder (PIT) tags (Cucherousset et al
2005, Rousel et al. 2004). It is perhaps telling of the relative novelty of stable
isotope analysis (SIA) in studies of fish movement that it merits a single
paragraph mention in a 33 page review (Lucas and Baras 2000).
5
1.4 Stable Isotope Analysis
Dietary analysis by gut-content sampling provides an indication of what a
fish has eaten in the previous hours. This can be very important in determining
the diet of the fish, and where it fits in the food-web. However, dietary items may
be difficult to identify after periods of digestion, and this technique provides only a
snapshot of what the fish ate immediately before capture. It cannot reveal long-
term trends in the diet.
Stable isotope analysis (SIA) is a relatively novel technique, only having
been applied in ecological studies in the past 25 years (e.g., Minagawa & Wada
1984, Peterson & Fry 1987, Hesslein et al. 1993, Hobson 1999, Galloway et al.
2003). SIA can be used to determine diet and trophic dynamics in a wide range
of animals, including fishes. Different tissues assimilate and turnover stable
isotopes at different rates (Pinnegar & Polunin 1999) and so the selection of
appropriate tissue allows this technique to be used for long- or short-term studies.
The stable isotope of 15N accumulates as one moves “up the food chain”
to higher trophic levels, resulting in higher δ15N values. This is likely due to the
preferential excretion of the lighter isotope 14N when forming nitrogenous waste
products (Jardine et al. 2003). There is some debate as to the average trophic
enrichment per trophic level. Minagawa and Wada (1984) showed an average
3.4‰ increase with each trophic level in combined lab and field studies, and this
figure is widely assumed throughout the literature. However, Vanderklift et al.
6 (2003) reviewed a number of lab-based enrichment studies, and arrived at a figure of approximately 2.5‰ for fish. Recent field studies (Vander Zanden and
Rasmussen 1999, Post 2002), however, confirmed the average 3.4‰ enrichment for temperate fishes in the natural environment. While it is clear that there is a great deal of variation in stepwise trophic enrichment, it seems reasonable to assume an average value of 3.4‰ in aquatic systems.
There have been many food web studies involving stable isotopes published recently (e.g., Grey et al. 2002, Schaus et al. 2002, Harvey et al.
2003), and the use of stable isotopes to trace fish movement has been gaining in popularity and use in recent years (e.g., Hobson 1999, Hansson et al. 1997).
Elements such as carbon and nitrogen naturally occur in different isotopes, differentiated based on the number of neutrons which they contain, and those atoms which retain their proton and neutron complements over time are known as stable isotopes. The ratio between these isotopes (13C/12C, 15N/14N), when compared to a standard, is known as the stable isotopic signature. The ratio of the rare, heavy isotope to the common, light isotope is expressed as the δ (delta) value (i.e. δ13C, δ15N) and is calculated using the following formula (using δ13C as an example):
13 13 12 13 12 δ C = {[( C/ Csample)/( C/ Cstandard)] -1} * 1000
7 where “sample” refers to the ratio within the sample and “standard” refers to a
universal standard used for the isotope being analysed (carbonate derived from
PeeDee Belemnite for δ13C, atmospheric nitrogen for δ15N; Jardine et al. 2003).
Different food-webs have different, and often unique, signatures based on a
number of intrinsic and extrinsic factors (e.g., terrestrial vs. freshwater vs. marine derived nutrients; anthropogenic effects), and these signatures are picked up by animals feeding within that food web. By analysing a small sample of tissue from a fish, its stable isotopic signature can be determined. When compared with
other individuals, both con-specifics and members of other species, and from
within and between food-webs, differences can be seen. Based on these
differences, and when corrected to a baseline of known trophic position (e.g.,
primary producer or primary consumer) the food-web being used by the
individual can be determined.
1.4.1 Stable Isotope Baselines
When attempting to derive food web structures using SIA, it is important to
establish a nitrogen baseline. This allows for the determination of trophic
position, and for comparison between different food webs. In many studies,
primary producers (littoral: algae, macrophytes, detritus; pelagic: plankton,
suspended particulate organic matter) are sampled directly. The drawback with
this is that they may show extensive temporal variation in isotopic signatures
(e.g., Post 2002) and thus require sampling over a broad temporal scale. It has
therefore been suggested (Cabana and Rasmussen 1996, Vander Zanden and
8 Rasmussen 1999, Post 2002) that long-lived primary consumers be used to
establish baseline values due to their known trophic level and assimilation of nutrients over a long temporal scale. Examples include snails (which feed at the
base of the littoral food web) and mussels (feeding at the base of the pelagic food web).
Unionid mussels have been shown to feed predominantly on fine
particulate organic matter (FPOM) derived from allochthonous (originating from
terrestrial nutrients) inputs in small stream systems (Christian et al. 2004).
Unionid mussels in rivers and lakes were shown to use bacterial carbons rather
than algal carbons as their main dietary source (Nichols and Garling, 2000).
Interspecies variation can be significant in the δ15N signatures of unionid
mussels, and some unionids may feed as omnivores rather than always as
primary consumers (Nichols and Garling 2000).
1.4.2 Selecting Stable Isotopes and Tissues
There are a variety of stable isotopes which can and have been be used
to infer movements of fish. Some of the more common isotopes used include 13C
15 13 and N. C varies between terrestrial C3 and C4 plants, between aquatic
benthic and pelagic food-webs, and between marine and freshwater sources
(Peterson & Fry 1987, Thorp at al. 1998). 15N varies between marine and
freshwater food-webs, and is indicative of trophic position. Other stable isotopes
which have been used include 2H, 18O, 17Cl, and 34S. δ15N also provides
9 information of trophic relationships due to the fact that 15N is accumulated with
each increase in trophic level, while δ13C provides information about food source.
Anthropogenic inputs can influence the isotopic signature of exposed
sites. Numerous studies have shown that human-induced changes in species composition (Vander Zanden et al. 1999, Johnson et al. 2002), sewage (e.g.,
Hobbie et al. 1990, Costanzo et al. 2001, Lake et al 2001, Wayland and Hobson
2001, deBruyn et al. 2003, Savage & Elmgren 2004), agricultural run-off (e.g.,
Harrington et al. 1998), aquaculture (e.g., Grey et al. 2004) and pulp and paper
effluent (e.g., Wayland and Hobson 2001, Galloway et al. 2003) are enriched in
δ15N, and that this enrichment manifests by elevating the δ15N signature of local
primary producers (such as algae), and consumers (such as invertebrates, fish, and birds). While many studies have looked at the impact of anthropogenic impacts at the food-web level, few studies have used this technique to trace movements of fishes exposed to nitrogen point sources. Hansson et al. (1997) used sewage treatment plant discharge rich in 15N as a marker to trace the
movements of small fish species in the Baltic Sea near Sweden. Harvey and
Kitchell (2000) used cities on Lake Superior as nitrogen point sources to
determine food-web dynamics as well as spatial heterogeneity and relative
movements of fishes. Harrington et al. (1998) used agriculturally enriched δ15N
to trace the movements of Atlantic salmon. δ13C may be depleted in pulp mill
effluent, due to the terrestrial carbon input resulting from the processing of trees.
Briers et al. (2004) artificially enriched a stream in δ15N to mark over 1.5 million
10 larval stoneflies; adults were recaptured and dispersal from the natal stream was assessed.
One of the benefits to stable isotope analysis is that it is not always necessary to sacrifice the fish to obtain a sample. In studies of δ13C, scales
alone can be used to determine diet. However, tissues such as scales and
bones are high in inorganic carbonate, which must be removed using acid
washing in order to analyse δ13C. This process significantly affects δ15N values,
so other tissues must be chosen in order to analyse δ15N. Stable isotope
turnover rates and variability differ among tissues, and can be affected by growth
rates. Pinnegar and Polunin (1999) showed white muscle tissue to be less
variable in δ13C and δ15N than red muscle, liver, or heart tissue. Low levels of
lipids in white muscle also forestall the need to remove these compounds, which
can increase variability in the sample. White muscle can be removed from larger
fish species using a biopsy of a small amount of tissue, without sacrificing the fish (Jake Vander Zanden, pers. comm. Center for Limnology, University of
Wisconsin at Madison). Smaller species and individuals, however, generally must still be sacrificed.
Turnover rates differ greatly among tissues as well. Liver tissue has been shown to have a rapid turnover rate, while bone has a very slow turnover rate.
White muscle tissue in adult fish has a turnover rate generally on the order of months (Jardine et al. 2003). In juvenile fish, however, this turnover rate is much
more rapid, and may take less than a month (Hesslein et al. 1993, Sakano et al.
2004). Migrating fish, and female fish which are allocating resources to eggs
11 may show relatively rapid turnover in their stable isotopic signature, as reserves are reallocated (Doucett at al. 1999). This maternally enriched δ15N signature is
expressed in newly-hatched young (Vander Zanden et al. 1998, Curry 2005). As
fish grow in size, many species undergo an ontogenetic dietary shift, which can affect the stable isotopic signature. When dealing with fish of different sizes, this must be taken into account (e.g., Genner et al. 2003, Johnson et al. 2004).
1.5 Objectives
The primary objectives of this thesis were to determine how local fish assemblages respond to pulp mill and municipal wastewater effluent; and to describe the movement patterns and site-fidelity of common fish species in the area of the pulp mill in Mactaquac Lake. Secondary objectives were to assess
the suitability and applicability of stable isotope analysis in freshwater fish
community and movement studies in temperate reservoirs receiving
anthropogenic inputs, and to use these findings to determine suitable sentinel
species and reference sites for environmental monitoring programs at this site.
This thesis is organized into 4 chapters: a general introduction, two research chapters, and a general discussion chapter. Chapter two describes fish community responses to pulp mill and municipal sewage effluents. Chapter three investigates the movement patterns of five fish species common to Mactaquac
Lake. Chapter four is a general discussion which summarizes and integrates chapters two and three, and details application of these results to environmental monitoring studies.
12 1.6 Literature Cited
BEAK. 1996. Cycle 1 EEM final interpretative report for St. Anne-Nackawic Pulp
Company Limited, Nackawic, New Brunswick. Beak International
Incorporated, Brampton, ON.
BEAK. 2000. Second Cycle EEM final interpretative report for St. Anne-Nackawic
Pulp Company Limited, Nackawic, New Brunswick. Beak International
Incorporated, Brampton, ON.
Bond, C.E. 1996. Biology of fishes. Saunders College Publishing, Toronto. 750
pp.
Briers, R.A., J.H.R. Gee, H.M. Cariss & R. Geoghegan. 2004. Inter-population
dispersal by adult stoneflies detected by stable isotope enrichment.
Freshwater Biology 49: 425-431.
Cabana, G. & J.B. Rasmussen. 1996. Comparison of aquatic food chains using
nitrogen isotopes. Proceedings of the National Academy of Sciences 93:
10844-10847.
Christian, A.D., B.N. Smith, D.J. Berg, J.C. Smoot & R.H. Findlay. 2004. Trophic
position and potential food sources of 2 species of unionid bivalves (Mollusca:
Unionidae) in 2 small Ohio streams. Journal of the North American
Bethological Society 23: 101-113.
Costanzo, S.D., M.J. O'Donohue, W.C. Dennison, N.R. Loneragan & M. Thomas.
2001. A new approach for detecting and mapping sewage impacts. Marine
Pollution Bulletin 42: 149-156.
13 Cucherousset, J., J. Roussel, R. Keeler, R. Cunjak & R. Stump. 2005. The use of
two new portable 12-mm PIT tag detectors to track small fish in shallow
streams. North American Journal of Fisheries Management 25: 270-274.
Curry, R.A. 2005. Assessing the reproductive contributions of sympatric
anadromous and freshwater-resident brook trout. Journal of Fish Biology 66:
741-757.
Curry, R.A. & K.R. Munkittrick. 2004. Fish community responses to multiple
stressors along the Saint John River, New Brunswick, Canada. In: J.N.
Rinne, R. Calamusso & R. Hughes (ed.) Changes in large river
assemblages in North America: Implications for management and
sustainability of native species, North American Journal of Fisheries
Management, In Press deBruyn, A.M.H., D.J. Marcogliese & J.B. Rasmussen. 2003. The role of sewage
in a large river food web. Canadian Journal of Fisheries and Aquatic Sciences
60: 1332-1344. deBruyn, A.M.H., K.S. McCann & J.B. Rasmussen. 2004. Migration supports
uneven consumer control in a sewage-enriched river food web. Journal of
Animal Ecology 73: 737-746.
Doherty, C.A. 2004. Movement patterns and biology of white sucker in a riverine
environment exposed to multiple stressors. M.Sc. Thesis, University of New
Brunswick, Fredericton. 100 pp.
Doucett, R.R., R.K. Booth, G. Power & R.S. McKinley. 1999. Effects of the
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20 N PEI DS4 NS NB * QC ME Mactaquac Lake Saint John River N DS3 1 000 1 000 m NB. Solid circles with captions “PME” and “STP” FB3 DS2 DS1 FB2 Pulp Mill PME US3 US2 FB1 STP US1 denote pulp mill and sewage treatment plant effluent outfalls, respectively. STP Nackawic Figure 1: Map of the study sites in Mactaquac Lake, NS Sewage Sewage Treatment Plant
21 2 FISH ASSEMBLAGE AND TROPHIC STRUCTURE IN A
TEMPERATE RESERVOIR RECEIVING ANTHROPOGENIC
INPUTS1
2.1 Abstract
Effluent from anthropogenic inputs can affect the fish communities in aquatic
ecosystems by altering species richness, diversity, and trophic structure. To
investigate the effects of a bleached kraft pulp mill and a municipal sewage
discharge on the fish community of a temperate reservoir, I combined standard
ecological methodologies with stable isotope analysis. While standard
methodologies and stable isotope analysis have been separately used in studies
to answer similar questions, their integration provides greater resolution than
either could alone. Species richness, diversity, and total catch were found to be
lower at sites exposed to pulp mill effluent, while sewage-exposed assemblages
had intermediate richness and diversity. Assemblages from reference sites
tended to have the highest scores in these indices. Stable isotope analysis of
δ13C and δ15N revealed that many species fed at higher relative trophic positions in the presence of effluents, and showed shifts towards increased reliance on
littorally derived resources. This may, in part, be due to decreased species
1 Jonathan A. Freedman, R. Allen Curry, & Kelly R. Munkittrick
22 diversity at these sites (leading to competitive release) and to nutrient enrichment manifest from the effluent discharge.
2.2 Introduction
Pulp mill effluent often has a nutrient enrichment effect (eutrophication) on receiving environments (Scrimgeour & Chambers 2000, Karels & Niemi 2002).
Increased nutrients to the base of the food web can then effect changes to higher trophic levels. However, these changes may not be consistent throughout the food web as they may affect some habitats, species, and trophic levels more than others (deBruyn et al. 2002, deBruyn et al. 2004, Karels & Niemi 2002,
Kovacs et al. 2002, Greenfield & Bart Jr. 2005) and the length of the food chain may be affected (Cabana & Rasmussen 1996). At low levels of nutrient enrichment, taxonomic diversity and overall abundance of macroinvertebrates increase, while they decrease as nutrient enrichment increases to toxic levels
(Culp et al. 2000).
Fish species which are sensitive to pollution, such as cyprinids, are affected to a greater degree than are pollution-tolerant species such as catostomids
(Karels & Niemi 2002, Kovacs et al. 2002, Greenfield & Bart Jr. 2005). Studies of the effects of anthropogenic inputs to aquatic ecosystems have found decreased cyprinid (minnow) abundance and diversity (Karels & Niemi 2002, deBruyn et al.
2004, Greenfield & Bart Jr. 2005) and decreased percid abundance (Karels &
Niemi 2002, Greenfield & Bart Jr. 2005) at sites exposed to these inputs. deBruyn et al. (2004) found increases in catostomid (sucker) and piscivore
23 abundance in a sewage-exposed system, while Greenfield and Bart (2005) found a decrease in sucker abundance in a stream exposed to pulp mill effluent.
It can be difficult to differentiate the relative effects of anthropogenic inputs
from natural biotic and abiotic factors on fish communities (Jackson et al. 2001,
Aguilar et al. 2003). Studies have shown that sewage (Lake et al. 2001,
Wayland & Hobson 2001, deBruyn et al. 2003), agricultural run-off (Harrington et
al. 1998, Gray et al. 2004), and pulp & paper effluent (Farwell 1999, Wayland &
Hobson 2001, Galloway et al. 2003) influence the δ15N signatures of local
primary producers (such as algae and phytoplankton), and consumers (such as
invertebrates, fishes, and birds). The presence or absence of predators, prey,
and competitors affect the trophic level of fishes, either by ecological constraints
such as niche exclusion or through competitive release (Vander Zanden et al.
1999); or by altering food web length and complexity (Cabana & Rasmussen
1996).
A relatively novel technique in determining community structure, stable
isotope analysis can be used to delineate food-web patterns and trophic
interactions (e.g., Cabana & Rasmussen 1996, Campbell et al. 2000, Grey et al.
2002, Vander Zanden & Vadeboncoeur 2002, Anderson & Cabana 2005). Stable
isotope analysis relies on the simple principle of “you are what you eat,” but
taken to another level – “you are also what your prey eats.” The most commonly
used isotopes in ecological studies are 13C and 15N. δ13C varies between
different primary producers – for instance terrestrial plants have different
signatures than aquatic plants, while phytoplankton differs from periphyton in
24 aquatic systems (REF???). These differences are conserved to higher trophic
levels, with a mean trophic fractionation of approximately 1‰ (Peterson & Fry
1987, Post 2002), allowing the basal links of food webs to be identified. δ15N is enriched by approximately 3.4‰ with each increasing trophic level (Minagawa &
Wada 1984, Peterson & Fry 1987, Post 2002), allowing for an estimate of trophic position when the baseline value of the primary producer is known.
Given that pulp mill effluent and municipal wastewater effluent are point- source anthropogenic inputs which affect nutrient dynamics, I sampled the fish community at 12 sites with varying degrees of effluent exposure, within a relatively small (~10 km) spatial scale. The structures of the fish assemblages at each site were assessed using both “standard” ecological methodologies
(species abundance, richness and diversity) and stable isotope analysis of δ13C and δ15N. While the “standard” methodologies were used to detect changes in
species composition and diversity associated with the effluent discharge sites,
stable isotope analyses was used to detect any changes in the trophic ecology
associated with these anthropogenic inputs, and will correlate any changes seen
in the ecological indices with anthropogenic effects.
I hypothesized that species which are susceptible to anthropogenically-
mediated nutrient enrichment will show marked trends in this study.
Furthermore, changes in abundance of these species and functional guilds at
impacted sites will alter the trophic dynamics by competitive release and niche
exclusion, while pollution-tolerant competitors will show converse trends.
Species feeding in the pelagic zone should be affected immediately downstream
25 from the PME discharge while littoral and benthic species should be affected
further downstream. By comparing and contrasting the results from both
analyses, we gain a greater understanding of the trophic dynamics and community structure than we could from either method alone.
2.3 Methods
2.3.1 Study Site
Mactaquac Lake is an impoundment of the Saint John River that was
formed by the creation of the Mactaquac hydroelectric dam in 1968. Maximum
depth of the lacustrine reach is approximately 28 m, and width ranges from 500
m to 1 000 m. The town of Nackawic is located approximately 40 km upstream
from the dam. The pulp mill is a bleached kraft hardwood mill whose effluent
undergoes primary and secondary treatment in several lagoons, which aerate the
effluent and allow particulate matter to settle out. The effluent holding time is
approximately 17 days, after which it is released into the lake by an offshore
multi-port diffuser located approximately 175 m offshore at a depth of several
meters, depending on the water level in the lake. The daily discharge rate
averaged approximately 61 500 m3 per day in 2003 (Stantec 2004).
The town of Nackawic discharges municipal sewage via a near-shore outfall located on the south bank of the river, approximately 1.5 km upstream of the mill’s discharge. The effluent receives secondary treatment by extended aeration, with a discharge rate of approximately 400 m3 per day. Fish were
26 sampled at twelve sites, located upstream (US), downstream (DS), and across the river (FB) from the mill’s effluent discharge, downstream of the sewage outfall
(STP), and in Nackawic stream (NS) (Figure 2).
2.3.2 Fish Community Sampling
Fish sampling took place from 16 to 25 June 2003 and 14 to 25 June
2004. Standardized sampling effort was used across all sites, except where otherwise indicated. One trap net with a 30m lead and 5cm mesh size was set in
3-5m of water, and retrieved the following morning after approximately 24 hours.
Sites FB1 or STP were not sampled by trap-net due to lack of suitable habitat.
Gangs of four 30.5m gillnets were set in mesh sizes ranging from 2.54 to 8.89cm for three repetitions of 30 minutes. Ten minnow traps and 1 Windermere trap were set overnight, for approximately 24 hours. Beach seines, 30m long with a mesh size of 1 cm were used to seine approximately 50m of shore. Where possible, one continuous seine was performed. At sites where the structure of the habitat rendered this impossible, two or three seines covering approximately
50 m of shoreline were performed. Site FB1 was not seined due to steep drop- offs. Targeted boat electrofishing was also used at some sites to collect samples for SIA, but these data were not included in the community analysis because boat electrofishing was not used at all sites. All fish were identified to species, with the exception of alewife (Alosa pseudoharangus) and blueback herring
(Alosa aestivalis) which could not be identified to species except through lethal sampling, and were grouped as Alosa spp. All fish not utilized for stable isotope
27 analysis were released. All research was approved by the University of New
Brunswick Animal Care Protocol Committee and was conducted under a
Canadian Department of Fisheries and Oceans Sampling permit.
2.3.3 Stable Isotope Analysis
2.3.3.1 Baselines
To reduce the temporal variability inherent in sampling primary producers
with high turnover such as phytoplankton and algae, it has been recommended
that long-lived primary consumers such as mussels and snails be used to
estimate stable isotopic baselines (Vander Zanden & Rasmussen 1999, Post
2002). To estimate both the pelagic and littoral food web baselines, we sampled
a filter-feeder (mussels, Mollusca: Unionidae) and an algal grazer (snails,
Gastropoda). Three mussels from each site were collected by hand, beach
seine, and Ekman grab, and immediately put on ice and frozen for later analysis.
Mussel foot tissue, selected for its relatively low variability (McKinney et al.
1999), was removed in the lab. Three snails from each site were collected by
hand from submerged woody debris and vegetation, kept alive for one day post-
collection to empty their guts, and then killed by freezing. They were then removed from their shells, rinsed in filtered water to remove any shell remnants, and dried whole.
28 2.3.3.2 Fish
Where available, three individuals of each fish species were sampled for
stable isotope analysis at each site, although in cases where insufficient numbers
were caught only one or two individuals were sampled. In species known to
have ontogenetic and size-mediated dietary shifts three individuals of each of the different size classes were sampled. Fish were sacrificed in the field, and
samples of dorsal white muscle tissue were excised from larger bodied fish, while
whole smaller fish were retained for analysis. Samples were stored in “whirl-pac”
sterile polyethylene bags, placed on ice in the field and kept frozen in the lab until
preparation. At the time of sample preparation, smaller fish were eviscerated,
skinned, de-finned, and decapitated.
2.3.3.3 Sample preparation
Samples were placed into 7 ml or 20 ml glass scintillation vials, and dried
in a drying oven for 48 h at 60o C. They were homogenized by being ground to a
fine powder using pestle and mortar. All implements were cleaned and
disinfected using acetone between samples. Samples were weighed into 0.2 mg
(± 10 %) aliquots, placed into 5 mm x 3.5 mm tin capsules, and analyzed for δ13C
and δ15N using either a Thermo-Finnigan Delta Plus or Delta XP isotope-ratio
mass spectrometer interfaced with a Carlo Erba NC2500 Elemental Analyzer via
the Conflo II or Conflo III, respectively.
δ15N and δ13C are determined from the same sample, and are calculated
using the formula:
29
δX = [(Rsample/Rstandard)-1] x 1000 (1)
where X refers to the rare, heavy isotope, and R is the ratio of the heavy isotope
(15N, 13C) to the light isotope (14N, 12C) in the sample and in a standard. The
standard for nitrogen is atmospheric nitrogen (AIR), and for carbon is carbon
dioxide derived from calcium carbonate in the Pee Dee Bee formation of South
Carolina (PDB). Approximately one sample in 15 was subsampled and analyzed
twice. Additionally, a standard sample of a yellow perch from Nackawic was
analyzed in every run and used to test for variation between runs. Four
International Atomic Energy Agency (IAEA) standards (N1, N2, CH6 and CH7) and three elemental standards (Acetanilide, Cyclohexanone, and Nicotinamide) were analyzed during each run. The standard deviation of the personal standard was
0.09 for δ13C and 0.17 for δ15N. The standard deviations of isotopic standards
ranged from 0.07 to 0.17 for δ13C and 0.07 to 0.26 for δ15N; and for elemental
standards ranged from 0.04 to 0.29 for δ13C and 0.08 to 0.23 for δ15N.
2.3.4 Data Analysis
Data from both sampling periods (2003 & 2004) were pooled for analyses
of species richness (number of species per site), abundance (number of
individuals per species per site), and diversity. Shannon-Wiener diversity (H’
loge) was used to calculate differences in diversity between sites. Results from the different sampling techniques were both analyzed separately and pooled
30 together for analysis. Non-parametric Kruskal-Wallis H tests were used to detect
differences between isotopes at different sites. Statistical analysis was performed using SYSTAT 10.2 (SPSS Inc., Chicago Il., U.S.A.) and Primer 5.2.2
(Primer-E Ltd., Plymouth UK).
Relative reliance on littoral and pelagic carbon sources by fishes was calculated using the formula:
13 13 13 13 -1 %litt. = (δ Ccons – δ Cpel) *( δ Clitt – δ Cpel) *100 (2)
13 13 where %litt. is the percent reliance on littoral sources expressed in δ C, δ Ccons
13 13 is the carbon signature of the consumer (fish), and δ Cpel and δ Clitt are the
carbon signatures of the pelagic and littoral baselines respectively of each site.
Relative trophic position was calculated using the formula:
15 15 -1 TP = 2 + (δ Ncons – δ Nbase)*3.4 (3a)
15 where TP is trophic position, δ Ncons is the nitrogen value for the consumer
15 (fish), and δ Nbase is the nitrogen baseline adjusted for differences in food source
(littoral or pelagic) using the formula:
15 15 15 δ Nbase = (%litt * δ Nlitt) + (%pel * δ Npel) (3b)
31
15 15 where %litt and %pel are calculated using equation 2, and δ Nlitt and δ Npel are,
respectively, the littoral and pelagic baseline nitrogen signatures of their sites.
Equation 3a was modified by adding 2, since primary consumers (trophic level 2)
were used to estimate baselines.
2.4 Results
2.4.1 Community Analysis
With 5 056 fish of 21 species caught during the community survey (Table
1), Shannon-Wiener diversity (H’loge) of the overall community was 1.86. One of
the sites immediately downstream of the pulp mill’s outfall (DS2) had the lowest
diversity (H’loge = 1.13) and species richness (S = 6) while the next site
downstream, DS3, had the lowest total catch (N = 285) and second lowest species richness (S = 9) of the ten sites where all sampling gears were used
(Figure 3). As a result of reduced effort (no trap net at either site, and no seine at
FB1), STP and FB1 had the lowest total catches (N = 59 and 136, respectively) but had relatively high diversity (H’loge = 1.77 and 1.45, respectively) due to the relatively high species richness at these sites (S = 8 at both sites, Figure 3).
The community had a log-normal distribution when plotted on a Whittaker plot, (Figure 4) as the eight most common species together comprised 98.6% of the total catch (Table 1 and Figures 4 & 5). White perch were the most abundant
species comprising 38.8% of the total catch, and comprised at least 25% of the
32 total catch at every site except US1, NS and STP (Figure 5). The fish assemblages at DS2 (67.4 %), FB2 (67.2 %), and DS4 (66.1 %) were heavily dominated by white perch likely accounting, at least in part, for the relatively low diversity at these sites (Figure 4). FB1 (25.7 %) and STP (16.7 %) had relatively high proportions of white sucker (Figure 5), likely as a result of the high proportion caught using gill-nets in the reduced sampling at these sites.
At NS, 821 fish were caught while the next highest site (US3) yielded only
600 fish (Table 1, Figure 4). This was largely driven by extremely high catches of juvenile and small-bodied fishes at NS while seining. Of the 821 total fish caught at this site, 369 were juvenile golden shiners while there were 117 banded killifish
(Table 1, Figure 5). Seining at the three US sites produced the lowest diversity of any site or capture method (Figure 3). While total seine catch was quite high
(N = 130 to 200), the littoral assemblages at these sites were dominated by banded killifish (Table 1, Figure 5). Fish assemblages at US sites STP and DS1 had higher proportions of banded killifish (21.2 – 42.3%, mean 27.4%) than those at other sites (0.3 – 16%, mean 8.3%).
2.4.2 Stable Isotope Analysis
Mussel δ15N was highest at DS2-DS4 (10.05 – 10.18 ‰) and was lowest at US3 (8.06 ‰) and US1 (8.85 ‰) (Figure 6). This suggests an impact of PME on the pelagic δ15N baseline at exposed sites. DS1 and STP were below the overall mean, suggesting that DS1 may not be exposed to the effluent, while the municipal wastewater effluent may not have a 15N enrichment effect. δ13C was
33 most enriched in mussels from FB1 (-31.99 ‰) and FB3 (-32.04 ‰), and most
depleted at US1-US3 (-30.76 – -30.89 ‰) (Figure 6). The upstream sites appear
to be clearly distinct in δ13C, but there was low variability among sites, with a maximum difference of just 1.28 ‰ in δ13C. There was a noticeable effect of
PME in mussels from DS3 and DS4 where significant differences were seen in
both δ13C and δ15N (Kruskal-Wallis, p=0.01 and p=0.03, respectively) compared
to other sites.
δ15N was lowest among snails from US3 (6.19 ‰) and NS (6.81 ‰) and
there was a decreasing trend from DS1-DS3 (6.88 – 7.29 ‰). Snails from DS
sites were all below the overall mean for littoral δ15N, while those from STP (8.14
‰) and US2 (7.90 ‰) were enriched (Figure 6). Snails from US2 (-26.9 ‰), NS
(-26.16 ‰), and FB1 (-25.87 ‰) were significantly depleted in δ13C than those
from other sites, while the most enriched were from US1 (-20.60 ‰), DS4 (-21.07
‰), and FB2 (-21.04 ‰) (Figure 6). Kruskal-Wallis tests revealed significant
differences between sites for both δ13C (p=0.007) and δ15N (p=0.01).
Neither δ13C nor δ15N revealed significant differences among banded
killifish (Kruskal-Wallis, p=0.6 and p=0.4 for δ13C and δ15N, respectively)
although banded killifish appeared to show enrichment in δ15N from DS1-3, and
enriched δ13C at DS sites relative to US and FB sites (Figure 6). Trophic position was highest in banded killifish from DS3 (TP: 3.85), where they also had a much stronger reliance on littoral resources than at other DS sites (%litt: 0.95; Table 2,
Figure 7), suggesting some impact of PME on the littoral resources.
34 While brown bullhead δ15N values were enriched at DS2, they were
relatively depleted at DS3, suggesting either that the bullhead at DS3 were not
impacted by the PME, or that they were affected in a different way (Figure 6).
Kruskal-Wallis tests revealed a significant difference in δ13C (p=0.04) but not in
δ15N (p=0.7) for this species. Brown bullhead from NS and STP sites had low
δ13C values, although these were quite variable. US sites were relatively depleted in δ15N, while the most enriched δ15N values were from DS2, which was
also depleted in 13C relative to the other DS sites. Bullhead from DS2 had the
highest trophic position (3.2) as well a lower reliance on littoral resources than
those from other DS sites (Table 2). By contrast, bullhead from DS3 had the
greatest reliance on littoral resources (47%) but an intermediate trophic position
(2.72) (Figure 7).
White sucker from FB1 were depleted in both 13C and 15N, while
individuals from FB3 were depleted in 15N relative to those from other sites
(Figure 6). While δ13C and δ15N were enriched at DS2 and DS3 relative to the
other DS sites, no significant differences were seen (Kruskal-Wallis, p=0.06 for
both δ13C and δ15N). Littoral reliance was highest at US2, DS2 and DS3 while
trophic position was highest at DS2 and DS3 and lowest at FB1 and FB3 (Table
2, Figure 7). Large pumpkinseed sunfish did not appear to be affected at DS
sites, but showed less reliance on littoral resources and lower trophic positions at the US sites (Table 2).
White perch δ13C at DS1 was enriched compared to the other sites, while
DS2 was depleted in δ15N compared to the other DS sites (Figure 6). Neither
35 δ13C nor δ15N revealed significant differences between sites (Kruskal-Wallis,
p=0.5 and p=0.25 for δ13C and δ15N, respectively). Trophic position in medium-
size white perch was highest at DS1, while trophic position in most other species
were impacted more at DS2 and DS3 (Table 2, Figure 7).
δ13C was less depleted in yellow perch from DS4 and DS2, and was most
depleted in FB1 and STP (Figure 6). DS2, DS4, NS, and FB3 had enriched δ15N values, while STP was depleted. While there was high variability at most sites, yellow perch at DS2 showed enriched isotopic signatures consistent with exposure to nutrient enrichment. Significant differences were seen in δ13C
(p=0.01) but not in δ15N (p=0.7). All size classes of yellow perch showed
increased reliance on littoral resources and increased trophic position at DS2 and
DS3 (Table 2) compared with sites other than those with strongly negative δ13C
baseline signatures (NS, FB1, US2). Medium sized yellow perch from DS1 had
the lowest trophic position (2.34) and reliance on littoral resources (20%),
followed closely by STP (2.62 and 23%, respectively) (Table 2, Figure 7).
2.5 Discussion
2.5.1 Fish Communities
The total abundance of fish close to the pulp mill’s outfall was reduced by
about 40% compared to other sites on that river bank, with associated declines in
species richness. Minnow species (Cyprinidae) were uncommon in the sampling
except at the stream site (NS), and appeared to be less abundant and diverse at
36 DS2 (0 individuals) and DS3 (1 individual each of 2 species) than at most other
sites (Table 1). Other studies of the effects of pulp mill effluent on fish
communities have identified similar trends. A 25-year study of fish community
dynamics in Florida streams revealed a higher total catch in a PME impacted
stream relative to a nearby reference stream. However, overall species diversity
and species richness were lower in the impacted stream as the local
assemblages were dominated by two species (Lepomis macrochirus and
Gambusia affinis) together comprising almost three-quarters of the total catch while cyprinids, catostomids and percids were greatly reduced (Greenfield & Bart
Jr. 2005). A study of a lacustrine fish community in relation to pulp and paper mill effluents in Finland found that while total abundance of fishes was higher at impacted sites, cyprinids (Phoxinus phoxinus) were less common and therefore appeared to be more sensitive to the effluents than other species (Karels & Niemi
2002).
Karels and Niemi (2002) also found that European perch (Perca fluviatilis) populations had rebounded from historical values due to improved filtration and cleaning of the effluent suggesting that they too are impacted by PME. deBruyn
et al. (2004) found that in a large river system impacted by municipal sewage, all
trophic levels responded to nutrient enrichment. However, smaller fish species
such as cyprinids were controlled by an increasing abundance of piscivores
resulting in a community dominated by catostomids (suckers) which were
generally too large for the piscivores to eat. This in turn led to an increase in
abundance of the prey of the smaller fish as top-down control was released. As
37 with this study site, theirs was an open system allowing for migration among sites. Unlike these previous studies, however, found that catostomid (white sucker) and percid (yellow perch) abundance did not appear to be impacted by
PME as both fell close to the overall mean values for these species at all sites
(Table 1). Low abundance of piscivores at DS2 and DS3 suggests that the relative absence of minnows was likely not a result of top-down control by predators. The relatively high abundance of white sucker at DS3 (Table 1,
Figures 3, 5), may be due to benthic nutrient enrichment from the PME settling to the bottom of the lake. In contrast, brown bullhead were most abundant at DS1, suggesting that bethic nutrient enrichment is driving abundance for this species.
No apex predators such as smallmouth bass or chain pickerel were caught at DS2 or DS3, but it is difficult to ascertain whether this absence is PME mediated, or due to sampling bias. Rare species may have been underestimated in this study. Large, uncommon species may frequently move among sites and the fact that they happen to have been caught at a site does not necessarily indicate residence. For instance, four large striped bass were caught in one trap net at one site, while no striped bass were caught at any other site (Table 1).
Additionally, some species may be underrepresented in the sampling due to their resistance to the sampling methods. American eels appeared to be quite abundant in an electrofishing survey, but only one was caught during the sampling. Many species, such as banded killifish, travel in schools (Scott &
Crossman 1973) so missing a school of fishes during the seine could well result in underestimating their total abundance at a given site and capture success may
38 be dependant more on chance than actual abundance. The absence of apex
predators and other rare species from some sites may be a result of sampling bias against rare species rather than actual absence.
The presence of large numbers of juvenile golden shiners at NS (Table 1,
Figure 5) suggest that this area may be used as a nursery for this species. Eight of the 11 total fallfish, and 2 of 3 northern redbelly dace were also caught at NS, together with 117 banded killifish and many juvenile pumpkinseed sunfish (Table
1). There were both submerged and emergent aquatic vegetation, so a great deal of habitat was available for these species and life-stages. The presence of piscivores such as chain pickerel, smallmouth bass, large white perch and large yellow perch suggests that this potential food source was well-exploited (Table
1).
2.5.2 How are stable isotope signatures affected by PME?
DS sites showed enriched pelagic (mussel) δ15N but depleted littoral
(snail) δ15N, while STP showed the opposite trend with depleted pelagic δ15N and enriched littoral δ15N (Figure 6). While the littoral zone is more impacted by
allochthonous terrestrial 15N sources, which largely accounts for system-wide
differences between littoral and pelagic baselines, this does not explain these
site-specific differences. It instead suggests that PME has a greater enriching
effect on pelagic δ15N baselines (phytoplankton), but potentially a depleting effect
on littoral primary production (periphyton). The STP discharge, on the other
hand, impacts the littoral zone more than the pelagic zone. These differences
39 probably result from differences in the effluent discharges; the pulp mill’s effluent
is discharged from a deep-water, offshore diffuser, while the sewage discharges
from near-shore (Stantec 2004). Both mussels (Cabana & Rasmussen 1996,
Lake et al. 2001) and snails (Cabana & Rasmussen 1996) show increased δ15N signatures with increased anthropogenic inputs. At some sites in this study enrichment or depletion was seen in both pelagic and littoral zones, as US1 and
US3 were both depleted in 15N. δ15N at US3 was significantly depleted in both
snails and mussels (Figure 6), suggesting a contaminant with a depleted δ15N signature such as ammonia or inorganic nitrogen which can result from sewage
(deBruyn et al. 2003), agriculture (Anderson & Cabana 2005), or human development (Cabana & Rasmussen 1996, McKinney et al. 2002) entering the lake at this source. The pulp mill uses ammonia as a nutrient in its effluent treatment system (Stantec 2004), but this would not enter the lake at this site but from the offshore diffuser, and no other effects attributable to PME in either community structure or stable isotopes were seen at this site.
There was a discrepancy in the magnitude of differences between the pelagic and littoral baselines for δ13C. Pelagic δ13C signatures ranged from -
30.76 at US1 to -32.04 at FB3, while littoral δ13C signatures ranged from -20.60
at US1 to -29.60 at US2 (Figure 6). This suggests a greater variety of carbon
sources, or more variable fractionation due to water flow conditions, in the littoral
zone relative to the pelagic zone. Terrestrial carbon has been shown to have
δ13C signatures ranging from -25 (Farwell 1999) to -30 (Benedito-Cecilio et al.
2000), and so may account for the lower values seen at sites US2, FB1 and NS if
40 allochthonous inputs are greater at these sites. Dube et al. (pers. comm. Dube,
M. Aquatic Ecosystem Impacts Research Branch, National Water Research
Institute, Environment Canada, Saskatoon SK, Canada) found effluent signatures
ranging from -25.5 to -14.7 for δ13C and from -4.0 to +2.6 for δ15N in a study of eleven pulp mills.
Higher water velocity has been shown to deplete 13C in algae, as slower
water flow creates a thicker boundary layer effectively limiting diffusion of 13C- enriched CO2 into the water (Hecky & Hesslein 1995, Trudeau & Rasmussen
2003). US2 and FB1 are both located at the junction of the riverine and
lacustrine reaches and are not as sheltered as some other sites, while NS is
located on a point at a bend in the Nackawic stream just before it enters
Mactaquac Lake. While we did not measure water velocity, these sites likely
experience lotic conditions (higher flow), thus potentially causing depletion in 13C relative to the other, lentic, sites. Since the δ13C of mussels was not affected, the
stable isotope signatures of phytoplankton appear to be less influenced by the
water velocity than those of the epiphyton and periphyton, as there would not be
boundary-layer limitations affecting the CO2 diffusion in the pelagic zone.
δ13C was enriched at DS sites relative to non-exposed sites in banded killifish, brown bullhead, and yellow perch, while δ15N was enriched in banded
killifish, brown bullhead, white sucker, and yellow perch but was depleted in white
perch (Figure 7). This suggests a clear effect of PME on the stable isotopic
signatures of fishes at these sites, consistent with other studies (Wayland &
Hobson 2001, Galloway et al. 2003, Skinner et al. in press). Banded killifish and
41 brown bullhead from STP were relatively depleted in δ13C, and yellow perch were
depleted in both δ13C and δ15N. White sucker were enriched in δ13C and δ15N at
STP, while banded killifish were enriched in δ15N. Wayland and Hobson (2001)
found enriched δ15N signatures at sites downstream from pulp mills, but
inconsistent results in δ13C with some sites showing enriched δ13C, and others
showing depleted δ13C signatures. Galloway et al. (2003) found depleted δ15N but enriched δ13C in slimy sculpin collected downstream from a pulp mill, but
increases in both δ13C and δ15N downstream from a paper mill. Wassenaar and
Culp (1996) found carbon and nitrogen signatures consistent with terrestrial
sources in the food web downstream from a pulp mill, and suggested that this
was due to incorporation by the microbial loop and epilithic algae, and transferred
to consumers. Fishes have been shown to have higher δ15N values downstream
from a sewage outfall (Hansson et al. 1997, deBruyn et al. 2003).
Increased trophic position is commonly seen in higher consumers at sites
exposed to nutrient enrichment (Cabana & Rasmussen 1996, Vander Zanden et
al. 1997, deBruyn et al. 2003). Eutrophication provides increased nutrients to
primary producers at the base of the food web, allowing for an increase in the
abundance, and potentially the diversity, of primary consumers (Gu et al. 1996,
deBruyn et al. 2002, deBruyn et al. 2003, Anderson & Cabana 2005). This
increased abundance of food sources can then lead to a trophic cascade and
increased abundance of higher-level consumers. Increased food web complexity
results in more linkages and therefore higher consumers experience shifts to
higher trophic positions (REFS HERE??? Post, Cabana). Human population
42 density increases δ15N, likely due to sewage inputs, and can affect food chains
leading up to fish by about one trophic level (Cabana & Rasmussen 1996).
In this study, small (< 10cm total length) littoral species, such as banded
killifish (mean TP = 3.25) and fourspine stickleback (TP = 3.39), fed at similar
trophic positions to species which are largely piscivorous such as smallmouth
bass (3.42), chain pickerel (3.33), large yellow perch (3.25), and large
pumpkinseed sunfish (3.21)(Table 2, Figure 7). These species were near the
apex of the aquatic food web; δ15N signatures of muskellunge and striped bass
from another study on the Saint John River revealed that muskellunge appear to
feed at a similar trophic position as smallmouth bass, with striped bass
approximately 0.3 trophic levels higher (R.A. Curry, unpublished data).
Intermediate δ13C values in these species suggest that they feed on both pelagic
and littoral prey and incorporate the stable isotopic signatures of both. This does not appear to be related to the PME as all sites show this same trend, and higher relative trophic positions in littoral species may indicate greater complexity of the
littoral food web relative to the pelagic food web (Figure 7). This may be
compounded by the littoral baseline being lower than the pelagic in δ15N, which is
consistent with other studies (Vander Zanden & Rasmussen 1999, Post 2002), and thus amplifying the relative trophic position of littoral fish species. Large
white perch appear to be wholly dependent on pelagic δ13C resources and, while
hypothesized to be largely piscivorous based on the literature (Scott & Crossman
1973), had a mean trophic position of just 2.98 (Table 2). This suggests that
either these white perch are feeding on alternate prey, or that their prey fish are
43 feeding at the level of primary consumers. This latter option seems probable,
due to the low trophic positions of pelagic forage fish such as small white perch
and northern redbelly dace (Figure 7).
Due to relatively steep grades of the banks of the river and anoxic
conditions in deeper water (Stantec 2003), the pelagic zone may be less
productive than the restricted littoral zone and, as such, the invertebrate food
web may be longer and more complex in the littoral zone than in the pelagic
zone. Alternatively, the littoral fish species may be exploiting alternative
resources which are high in δ15N. For instance, sticklebacks have been known to
eat eggs of their own and other fish species (Scott & Crossman 1973). While we
found no evidence in the literature that banded killifish consume fish eggs, they
are a logical source of nutrients to be exploited by such a generalist species.
Since fish eggs have been shown to show maternal δ15N (Doucett et al. 1999,
Curry 2005), consuming fish eggs as a portion of the diet could enrich their δ15N
signature. However, it is doubtful that they consume enough fish eggs to have
such a major effect on their stable isotopic signature.
Additionally, the trophic positions of pelagic-feeding species such as white
perch may be overestimated (Figure 7). It is assumed that the unionid mussels
used for a baseline are feeding at a trophic level of two (primary consumer)
which is consistent with studies by Cabana and Rasmussen (1996), Vander
Zanden and Rasmussen (1999) and Post (2002). However, it has been shown that some unionid mussels are omnivorous, consuming both zooplankton and phytoplankton, and thus enriching their trophic position to the range of 2.5 rather
44 than 2 (Nichols & Garling 2000). Assuming that this is the case, and there is an
element of omnivory in the baseline mussels, the estimated trophic positions for
pelagic fish species may be up to 0.5 too low. However, since other studies have
found a similar pattern of δ15N among a range of invertebrate taxa, including mussels and snails, in temperate lakes (Vander Zanden & Rasmussen 1999,
Post 2002), we feel comfortable in assuming that the mussels are indeed feeding as secondary consumers.
2.5.3 Conclusions and Integration
In this study, fish abundance and diversity were negatively related to PME
exposure. Cyprinids were less common at PME exposed sites, suggesting
increased sensitivity to PME or to PME mediated nutrient enrichment, and may therefore be indicative of impacted communities. This and other studies (Kovacs et al. 2002, Greenfield & Bart Jr. 2005) have shown that cyprinid abundance may therefore be an appropriate indicator species for impacted systems. White perch were the most common and widespread species, and were especially dominant at DS sites, where diversity, richness and abundance were lower overall (Figure
3). While the abundance of species such as yellow perch did not appear to be affected by PME, changes in their trophic positions and carbon sources suggest that there is in fact an impact. Yellow perch condition was significantly higher at
DS2 than at other sites (See Chapter 3) suggesting that these effects are
biologically significant.
45 Since the littoral food web does not appear to be subsidized by PME, the
reason for shifts to increased littoral reliance in some species at the DS sites is
unknown. I would hypothesize that, if anything, the pelagic food web would be
impacted to a greater extent than the littoral food web due to the incorporation of
PME derived nutrients by phytoplankton in the water column. This is
demonstrated by higher δ15N values in mussels from DS sites relative to non-
PME impacted sites. Snails, on the other hand, show a slight decrease in δ15N values at DS sites. The assimilation of PME-derived nutrients into the microbial- based food web may play a significant role in these differences.
Some of the conclusions from either methodology could be inferred from the other. For instance, increased species diversity would suggest higher food- web complexity, and vice-versa. However, stable isotope analysis reveals very little about relative species abundances both within and between sites. It cannot provide as much information about the diversity of the sites as the traditional methodologies. Differences in relative abundance, species richness and diversity are important to the understanding of the structure of the assemblage and are not revealed by stable isotope analysis alone.
The traditional methodologies provide almost no information about the trophic dynamics or food-web structure of the assemblages, except that which can be inferred from knowing the ecology of the species. For instance, in this study smallmouth bass and chain pickerel were hypothesized to be piscivores, as were large yellow perch and white perch. However, stable isotope analysis revealed that white perch feed primarily on pelagic resources while yellow perch
46 consume primarily littorally derived nutrients, and smallmouth bass and chain
pickerel assimilate signatures from both littoral and pelagic zones (Figure 7).
There is individual variation in that while most large white perch are indeed
piscivores, some appear to feed as primary consumers (at sites DS2 and FB2;
Figure 7). Stable isotope analysis also revealed no trophic interactions between white perch and yellow perch. Stable isotope analysis and traditional ecological methodologies provide different, but complementary information. As such, they should be used in collaboration with one another to answer appropriate
ecological questions.
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53
Table 1. Total numbers of fish species caught at 12 sites in Mactaquac Lake, NB,
giving common name, scientific name, and abbreviated name for each
species.
54 Abbrev. Common Name Scientific Name US1 US2 US3 Cyprinidae CC Creek Chub Semotilus atromaculatus 0 0 0 CS Common Shiner Luxilus cornutus 0 2 0 FF Fall Fish Semotilus corporalis 0 1 1
GS Golden Shiner Notemigonus crysoleucas 1 2 5
NRBD Northern Redbelly Dace Phoxinus eos 0 0 0 PD Pearl Dace Margariscus margarita 0 0 0
Planktivore AL Alewife and blueback herring Alosa spp. 29 85 34
Small littoral species 4SSB Fourspine Stickleback Apeltes quadracus 4 1 0 BKF Banded Killifish Fundulus diaphanus 196 129 142
Benthivores BBH Brown Bullhead Ameirus nebulosus 68 54 19 WS White Sucker Catostomus commersoni 23 30 28
Omnivores/trophic ontogeny AS Atlantic Salmon Salmo salar 0 0 0 BT Brook Trout Salvelinus fontinalis 0 0 0 PSS Pumpkinseed Sunfish Lepomis gibbosus 5 14 5 WP White Perch Morone americana 16 127 310 YP Yellow Perch Perca flavescens 118 64 55
Piscivores SMB Smallmouth Bass Micropterus dolomieui 1 3 0 SB Striped Bass Morone saxatilis 0 0 0 AE American Eel Anguilla rostrata 1 0 0 CP Chain Pickerel Esox niger 0 1 1 MUSK Muskellunge Esox masquinongy 1 1 0
TOTALS 463 514 600
55 Abbrev. DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP TOTAL Cyprinidae CC 0 0 1 0 0 0 0 0 0 1 CS 0 0 0 0 0 1 1 0 2 6 FF 0 0 0 0 0 1 0 8 0 11 GS 2 0 1 5 0 3 1 380 0 400 NRBD 1 0 0 0 0 0 0 2 0 3 PD 0 0 0 0 0 0 1 0 0 1
Planktivore AL 34 29 9 37 13 11 25 22 4 332
Small littoral species 4SSB 1 0 0 0 1 1 0 0 0 8 BKF 110 6 10 14 0 1 82 117 13 820
Benthivores BBH 121 11 18 30 2 17 2 59 1 402 WS 18 18 37 22 35 9 36 19 10 285
Omnivores/trophic ontogeny AS 0 0 0 0 0 0 1 0 0 1 BT 0 0 0 2 0 1 0 0 0 3 PSS 19 6 6 15 3 8 3 62 3 149 WP 147 240 162 334 59 195 290 74 7 1961 YP 62 46 41 44 22 38 57 70 19 636
Piscivores SMB 4 0 0 2 1 3 2 2 0 18 SB 0 0 0 0 0 0 4 0 0 4 AE 0 0 0 0 0 0 0 0 0 1 CP 1 0 0 0 0 1 1 6 0 11 MUSK 0 0 0 0 0 0 1 0 0 3
TOTALS 520 356 285 505 136 290 507 821 59 5056
56
Table 2. Mean proportion of reliance on littoral resources (“Litt.,” from δ13C
analysis) and mean trophic position (“T.P.,” from δ15N analysis) for fish
species from 12 sites in Mactaquac Lake, NB. Species abbreviations
are as described in Table 1, while the suffixes “sm,” “med,” and “lg”
denote small (<15cm fork-length for WS, <10cm for other species),
medium (10-18cm for WP, 10-16cm for YP), and large (>10 cm for CS,
FF, GS and PSS, >15cm for WS, >18cm for WP, and >16cm for YP)
sized fish, respectively.
57 US1 US2 US3 DS1 DS2 DS3 Species Litt. T.P. Litt. T.P. Litt. T.P. Litt. T.P. Litt. T.P. Litt. T.P. Cyprinidae CC 0.55 3.12 CS sm 0.04 2.33 CS lg 0.79 3.19 0.41 3.17 FF sm 0.64 2.84 FF lg 0.84 3.49 0.37 3.12 0.57 3.16 GS sm 0.26 2.93 0.36 2.88 0.44 2.87 0.46 3.00 GS lg 1.00 3.54 0.44 2.53 0.52 2.72 NRBD 0.00 2.44 PD
Small littoral species 4SSB 0.55 3.82 1.00 3.76 0.65 3.48 BKF 0.66 3.50 1.00 3.61 0.60 3.30 0.82 3.48 0.82 3.62 0.95 3.85
Benthivores BBH 0.23 2.38 0.40 2.25 0.39 2.78 0.38 2.94 0.28 3.20 0.47 2.72 WS sm 0.93 3.22 WS 0.30 2.70 0.88 2.92 0.40 2.79 0.32 2.84 0.41 3.17 0.43 3.03
Omnivores BT PSS sm 0.46 3.46 0.35 3.44 PSS lg 0.39 3.31 0.67 3.62 0.58 2.98 0.75 3.75 0.72 3.73 0.80 3.81 WP sm 0.00 1.99 0.01 2.05 WP med 0.01 2.53 0.41 2.86 0.07 2.75 0.14 3.42 0.18 2.65 0.03 2.69 WP lg 0.13 3.58 0.28 3.60 0.18 3.62 0.27 2.74 0.25 3.58 YP sm 0.10 2.98 0.54 3.14 0.55 3.16 0.59 3.55 0.69 3.77 YP med 0.86 3.60 0.79 3.36 0.20 2.34 0.82 3.84 YP lg 0.45 3.76 0.80 3.75 0.42 3.47 0.66 3.79 0.80 3.85 0.64 3.63
Piscivores CP 1.00 4.25 0.57 3.10 0.56 3.84 SMB 0.49 3.88
58 DS4 FB1 FB2 FB3 NS STP Species Litt. T.P. Litt. T.P. Litt. T.P. Litt. T.P. Litt. T.P. Litt. T.P. Cyprinidae CC 0.50 2.49 CS sm CS lg 0.23 3.15 FF sm 0.64 2.82 FF lg 0.47 3.20 0.57 3.12 GS sm 0.34 3.01 0.69 3.21 0.40 2.27 0.57 3.21 0.36 2.96 GS lg 0.47 2.44 0.57 2.71 0.68 3.22 1.00 3.29 0.64 2.44 NRBD 0.02 2.30 PD 0.55 3.04
Small littoral species 4SSB 0.65 3.60 BKF 0.83 3.58 0.92 3.64 0.70 3.44 0.96 3.71 0.96 3.59 0.72 3.54
Benthivores BBH 0.38 2.79 0.29 2.56 0.44 3.04 0.15 2.85 0.00 2.74 WS sm 1.00 3.31 WS 0.25 2.83 0.15 1.87 0.30 2.87 0.25 1.99 0.02 2.57 0.42 2.95
Omnivores BT 0.56 3.24 PSS 0.51 3.74 0.84 3.56 0.52 3.39 0.49 3.37 0.88 3.81 0.36 3.16 PSS lg 0.42 3.72 0.79 3.63 0.80 3.99 0.78 3.63 WP sm WP 0.12 2.82 0.22 2.76 0.06 2.51 0.17 3.00 0.28 3.02 0.02 2.22 WP lg 0.17 3.13 0.21 2.53 0.25 3.26 0.43 4.04 YP sm 0.34 3.27 0.30 3.06 0.37 3.50 0.26 3.09 YP med 0.79 3.67 0.36 3.08 0.27 3.34 0.92 3.92 0.23 2.62 YP lg 0.42 3.23 0.51 3.50 0.80 3.93
Piscivores CP 0.51 3.50 0.61 4.06 0.68 3.79 SMB 0.41 3.67 0.42 3.70 0.71 3.92
59
US1 US2 US3 DS1 N S.D. S.D. N S.D. S.D. N S.D. S.D. N S.D. S.D. Species %litt T.P. %litt T.P. %litt T.P. %litt T.P. Cyprinidae CC CS sm 2 0.059 0.136 CS lg 2 0.2700.141 1 FF sm FF lg 1 1 1 GS sm 4 0.084 0.154 1 2 0.0020.013 GS lg 1 5 0.1590.515 3 0.1740.244 NRBD 1 PD
Small littoral species 4SSB 3 0.071 0.118 1 2 0.0870.137 BKF 3 0.067 0.201 3 0.000 0.151 3 0.130 0.247 3 0.116 0.041
Benthivores BBH 3 0.107 0.341 3 0.368 0.230 3 0.086 0.284 3 0.045 0.250 WS sm 3 0.1250.268 WS 3 0.265 0.466 3 0.205 0.581 3 0.162 0.756 3 0.185 0.683
Omnivores BT PSS sm 2 0.276 0.292 3 0.0310.116 PSS lg 5 0.210 0.351 3 0.367 0.387 3 0.142 0.498 3 0.170 0.158 WP sm 3 0.000 0.052 3 0.021 0.231 WP 3 med 0.011 0.206 1 2 0.001 0.218 3 0.077 0.069 WP lg 2 0.042 0.482 2 0.108 0.604 1 YP sm 1 2 0.029 0.164 3 0.332 0.151 YP med 2 0.1910.418 1 1 YP lg 3 0.083 0.117 3 0.280 0.077 3 0.185 0.234 3 0.118 0.492
Piscivores CP 1 1 1 SMB 2 0.0140.100
60 DS2 DS3 DS4 FB1 N S.D. S.D. N S.D. S.D. N S.D. S.D. N S.D. S.D. Species %litt T.P. %litt T.P. %litt T.P. %litt T.P. Cyprinidae CC 1 1 CS sm CS lg FF sm 1 FF lg 1 2 0.100 0.042 3 0.115 0.188 GS sm 1 3 0.143 0.095 3 0.112 0.320 3 0.018 0.216 GS lg 2 0.016 0.059 NRBD PD
Small littoral species 4SSB BKF 3 0.027 0.018 3 0.039 0.044 3 0.040 0.228 2 0.021 0.024
Benthivores BBH 3 0.178 0.261 3 0.025 0.114 3 0.102 0.447 WS sm WS 3 0.085 0.341 3 0.375 0.592 3 0.090 0.353 2 0.136 0.197
Omnivores BT 1 PSS sm 1 2 0.071 0.081 4 0.126 0.167 PSS lg 2 0.040 0.098 3 0.045 0.066 2 0.113 0.333 2 0.296 0.575 WP sm WP med 4 0.138 0.347 1 4 0.073 0.207 3 0.167 0.494 WP lg 1 2 0.022 0.241 1 YP sm 2 0.117 0.101 2 0.241 0.038 3 0.102 0.168 YP med 1 3 0.051 0.082 3 0.216 0.590 YP lg 3 0.224 0.036 3 0.101 0.139
Piscivores CP SMB 2 0.028 0.145
61 FB2 FB3 NS STP N S.D. S.D. N S.D. S.D. N S.D. S.D. N S.D. S.D. Species %litt T.P. %litt T.P. %litt T.P. %litt T.P. Cyprinidae CC CS sm CS lg 1 FF sm 3 0.0810.072 FF lg 2 0.084 0.056 GS sm 1 4 0.2060.149 3 0.0350.056 GS lg 3 0.100 0.2191 1 1 NRBD 1 PD 1
Small littoral species 4SSB 1 BKF 2 0.063 0.1583 0.041 0.083 3 0.073 0.116 3 0.092 0.138
Benthivores BBH 3 0.134 0.1772 0.233 0.159 3 0.264 0.564 3 0.000 0.347 WS sm 1 WS 3 0.154 0.4673 0.2190.498 2 0.032 0.247 3 0.085 0.226
Omnivores BT PSS sm 4 0.134 0.069 2 0.030 0.115 3 0.160 0.130 3 0.267 0.343 PSS lg 1 2 0.0460.120 WP sm WP 2 3 4 3 med 0.107 0.131 0.126 0.360 0.282 0.377 0.026 0.323 WP lg 1 2 0.0150.528 1 YP sm 4 0.181 0.3311 4 0.0190.199 YP med 3 0.080 0.333 4 0.154 0.117 5 0.176 0.242 YP lg 3 0.056 0.278 4 0.239 0.442 6 0.209 0.376
Piscivores CP 1 1 3 0.2160.411 SMB 2 0.038 0.085 1
62 N PEI DS4 NS les with captions “PME” NB * QC wnstream sites, FB: far-bank ME Mactaquac Lake Saint John River stream site. Solid circ N DS3 1 000 1 000 m FB3 DS2 Lake, NB. US: upstream sites, DS: do upstream sites, DS: Lake, NB. US: DS1 FB2 Pulp Mill PME US3 US2 FB1 STP US1 STP and “STP” denote pulp mill sewage treatment plant effluent outfalls, respectively. STP: sewage treatment plant discharge site, NS: Nackawic Nackawic NS Sewage Sewage Treatment Plant Figure 2: Map of study sites in Mactaquac
63 Total Catch Species Richness Shannon-Wiener Diversity 1000 16 2.0 14 800 12 1.5 10 600 8 1.0 400 6 4 0.5 200 2
0 0 0.0 2 1 3 1 3 1 3 2 2 P 2 1 3 1 3 B B NS B NS B B NS US1 US US3 DS DS2 DS DS4 F FB2 F STP US US2 US DS1 DS DS3 DS4 FB1 F FB3 ST US1 US US3 DS DS2 DS DS4 F FB2 F STP 250 10 2.0 Gill-Net Gill-Net Gill-Net 1.8 200 8 1.6 1.4 150 6 1.2 1.0 100 4 0.8 0.6 50 2 0.4 0.2 0 0 0.0 2 3 2 4 1 2 P 1 3 2 4 1 3 1 3 2 3 2 B T NS B2 NS B NS US1 US US DS1 DS DS3 DS FB F FB3 S US US2 US DS1 DS DS3 DS FB F FB STP US US2 US DS1 DS DS DS4 FB1 F FB3 STP
500 12 1.8 Trap-Net Trap-Net Trap-Net 1.6 10 400 1.4 8 1.2 300 1.0 6 0.8 200 4 0.6 0.4 100 2 0.2 0 0 0.0 1 3 2 4 1 3 1 3 3 1 2 3 P 2 1 3 2 B2 NS B NS B1 B3 TP NS US US2 US DS1 DS DS3 DS FB F FB STP US US2 US DS1 DS2 DS DS4 FB F FB ST US1 US US3 DS DS2 DS DS4 F FB F S 700 10 1.4 Seine Seine Seine 1.2 8 600 1.0 6 0.8
0.6 200 4 0.4 100 2 0.2
0 0 0.0 2 3 2 4 1 3 P 2 1 3 2 P 2 1 3 1 3 T NS B T NS B B NS US1 US US DS1 DS DS3 DS FB FB2 FB S US1 US US3 DS DS2 DS DS4 FB1 F FB3 S US1 US US3 DS DS2 DS DS4 F FB2 F STP
Figure 3: Total Catch (# individuals caught per site), Species Richness (# species
caught per site), and Shannon-Wiener Diversity (H’loge) of fish caught
at 12 sites in Mactaquac Lake, NB. Total pooled values are given, as
are those for different capture techniques: gill-nets, trap-nets, and
beach seines. Trap nets were not used at FB1 or STP, and seines
were not used at FB1.
64
10000
1000
100 # indivs (log) indivs #
10
1 0 3 6 9 12 15 18 21 species rank order
Figure 4: Whittaker plot of species rank abundance and total catch of fish caught
in Mactaquac Lake, NB.
65
1.0
Other Species
0.8 YellowPerch White Suckers
White Perch 0.6 Banded Killifish Brown Bullhead
0.4 Proportion of Catch Proportion
0.2
0.0 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP Site
Figure 5: Relative proportion of catch for 5 common fish species at 12 sites in Mactaquac Lake, NB. All other species are grouped into the “Other Species” category.
66
Figure 6: Line graphs of mean δ13C and δ15N (± SE) for baselines (mussels and
snails) and five common fish species from sites in Mactaquac Lake, NB.
67
-18 9.0 Snails SE Snails SE
8.5 -20
8.0 -22
7.5 d15N d13C -24 7.0
-26 6.5
-28 6.0 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP
-30.0 11.0 Mussels SE Mussels SE 10.5 -30.5
10.0 -31.0
9.5 -31.5 d13C d15N 9.0
-32.0 8.5
-32.5 8.0
-33.0 7.5 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP
-22 12.8 Banded Killifish, SE Banded Killifish, SE 12.6 -23 12.4
12.2 -24 12.0
-25 11.8 d13C d15N 11.6 -26 11.4
11.2 -27 11.0
-28 10.8 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP
-24 13 Brown Bullhead SE Brown Bullhead SE -26 12
-28 11
-30 10 d13C d15N -32
9 -34
8 -36
-38 7 US1 US2 US3 DS1 DS2 DS3 DS4 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB2 FB3 NS STP
68 -24 15 White Perch >14cm SE White Perch >14cm SE 14 -26
13 -28
12 -30 d13C d15N 11
-32 10
-34 9
-36 8 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS
-22 13 White Sucker SE White Sucker SE -24 12
11 -26
10 -28 9 d13C -30 d15N 8
-32 7
-34 6
-36 5 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP
-20 16 Yellow Perch >12cm SE Yellow Perch >12cm SE -22 15
-24 14
-26 13 -28 12 d13C -30 d15N 11 -32
10 -34
-36 9
-38 8 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP Site Site
69 Figure 7: Bivariate plots of δ13C and δ15N for fish assemblages at 12 sites in
Mactaquac Lake, NB. Error bars indicate ± SE; fish species
abbreviations are given in Table 1; “Sn” indicates snails and “Ms”
indicates mussels; and the suffixes “sm,” “med,” and “lg” denote small-
(<15cm fork-length for WS, <10cm for other species), medium- (10-
18cm for WP, 10-16cm for YP), and large- (>10 cm for CS, FF, GS and
PSS, >15cm for WS, >18cm for WP, and >16cm for YP) sized fishes,
respectively. Symbols indicate feeding group (□ – baseline, ● – benthic
invertivore, ○ – pelagic invertivore, ▲ – piscivore).
70 16 16 DS1 FB1
14 SMB 14 CP YP lg WP med PSS sm PSS lg PSS lg 12 12 PSS sm 4SSB YP med BKF BKF BBH WS GS sm GS sm FF 10 NRBD 10 Ms WP med
GS lg Ms YP med CC 8 8 Sn Sn
WS
6 6 -34 -32 -30 -28 -26 -24 -22 -20 -34 -32 -30 -28 -26 -24 -22 -20
16 16 DS2 FB2
14 14 YP lg SMB
YP sm CP 4SSB 12 BBH 12 FF lg PSS lg BKF CS lg PSS sm BKF WS YP sm YP lg Ms GS sm FF lg 10 10 WP med WS WP lg BBH WP med Ms GS lg WP lg 8 8 Sn Sn
6 6 -34 -32 -30 -28 -26 -24 -22 -20 -34 -32 -30 -28 -26 -24 -22 -20
16 16 DS3 FB3 CP 14 14 WP lg PSS lg YP sm YP sm WP lg YP med YP med YP lg BKF 12 PSS lg WP med PSS sm BKF 12 YP lg BBH GS lg WS CC 10 PD WP med Ms GS sm 10 Ms GS sm 8 BBH FF sm Sn WS 8 6 Sn
6 4 -34 -32 -30 -28 -26 -24 -22 -20 -34 -32 -30 -28 -26 -24 -22 -20
71 16 16 DS4 US1
PSS lg 14 14 WP lg YP lg 4SSB SMB PSS sm YP med YP sm PSS sm 12 WP lg FF lg 12 BKF BKF BT YP sm PSS lg WP med GS sm GS sm WP med 10 Ms WS 10 BBH WS
GSlg Ms BBH 8 8 Sn Sn
6 6 -34-32-30-28-26-24-22-20 -34 -32 -30 -28 -26 -24 -22 -20
16 16 NS US2
WP lg CP 14 14 SMB YP lg YP med WP lg PSS lg CP YP lg YP med 4SSB 12 PSS sm 12 GS lg WP med GS sm BKF FF lg BBH YP sm BKF GS lg CS lg 10 10 Ms WP med WS sm WS Ms FF sm WS Dace 8 8 BBH WP sm Sn Sn
6 6 -34 -32 -30 -28 -26 -24 -22 -20 -34 -32 -30 -28 -26 -24 -22 -20
16 16 STP US3
14 14 WP lg YP lg PSS lg 12 12 BKF YP sm YP med PSS sm BKF FF lg CS lg BBH WP med GS sm YP sm CP WS WS 10 GS med 10 PSS lg Ms CS sm BBH YP med GS lg GS lg Sn WP sm WP med 8 8 Ms
Sn 6 6 -34 -32 -30 -28 -26 -24 -22 -20 -34 -32 -30 -28 -26 -24 -22 -20
72 3 TRACKING MOVEMENT PATTERNS AND SITE FIDELITY OF
FISHES IN A TEMPERATE RESERVOIR USING STABLE
ISOTOPES2
3.1 Abstract
We investigated the movement patterns of five common fish species in
Mactaquac Lake, New Brunswick, Canada, using stable isotope analysis of δ13C and δ15N. We took advantage of the unique signatures resulting from a point-
source input (a pulp mill’s effluent discharge) to investigate movements at a
relatively small spatial scale (~10 km). Discriminant analysis of the stable isotopes revealed that while white perch (Morone americana) appear to show a great deal of movement within the system, yellow perch (Perca flavescens) show high home-range fidelity. Brown bullhead (Ameirus nebulosus) and white sucker
(Catostomus commersoni) show intermediate degrees of movement and site fidelity, although in the case of the white sucker this may be confounded by a vernal spawning migration. Banded killifish (Fundulus diaphanus) appear to show relatively low site fidelity, but this may be evidence of a lack of exposure to
2 Jonathan A. Freedman, R. Allen Curry, & Kelly R. Munkittrick
73 the effluent rather than of actual fish movement. Analysis of fish condition
supports these findings.
3.2 Introduction
Understanding the movements and migrations of fishes plays a fundamental role in how we interpret the ecological data of fish communities.
Recently, biogeochemical markers such as stable isotopes have been used to trace animal movement a posteriori by inferring past animal movement from the
stable isotopic signature (Hansson et al. 1997, Hobson 1999, Rubenstein &
Hobson 2004). Stable isotope analysis (SIA) is a relatively novel technique in
biology and is emerging as a very powerful tool for assessing a variety of
ecological parameters including food web dynamics (Cabana & Rasmussen
1996, Campbell et al. 2000, Vander Zanden & Vadeboncoeur 2002), tracing
contaminants (Vander Zanden & Rasmussen 1996, Kidd et al. 1999, Campbell et
al. 2000), and detecting animal movements and site fidelity (Hansson et al. 1997,
Hobson 1999, Farwell 1999, Galloway et al. 2003, Gray et al. 2004, Harrod et al.
2005). The stable isotopic signature is the ratio of the rare, heavy isotope (e.g.
13C, 15N) to the common, lighter isotope (e.g. 12C, 14N). While 13C remains fairly
constant across trophic levels, 15N is enriched at the rate of approximately 3.4‰
with each increasing trophic level (Minagawa & Wada 1984, Peterson & Fry
1987, Vander Zanden & Rasmussen 1999, Post 2002).
Differences in stable isotopic signatures develop and are manifest at the
lowest trophic positions and are retained, in varying degrees, by higher trophic
levels. It has therefore proven relatively easy to ascertain movements between
74 different habitats such as marine and freshwater (Hesslein et al. 1991, Kline et al.
1998, Curry 2005, Harrod et al. 2005), due to large differences in the baseline isotopic signatures between marine and freshwater primary producers. However, determining movements within a system or habitat can be more challenging as there is less variation in the baseline isotopic signatures, and differences are therefore more subtle. Anthropogenic inputs can be used as natural markers to identify movements between impacted and non-impacted sites as they can affect the food web and isotopic baselines. Run-off from agriculture (Harrington et al.
1998, Gray et al. 2004), waste from aquaculture facilities (Grey et al. 2004), and effluent from sewage (Hansson et al. 1997, Wayland & Hobson 2001, deBruyn et al. 2003) and pulp mills (Wayland & Hobson 2001, Galloway et al. 2003, Skinner et al. in press) can result in unique isotopic signatures at higher trophic levels.
This is likely due, in part, to increased primary production (Scrimgeour &
Chambers 2000, Karels & Niemi 2002, deBruyn et al. 2003) and from the
increased input of terrestrial carbon sources (Farwell 1999, Wassenaar & Culp
1996).
I investigated the movements of common fish species at a relatively small
spatial scale (~10 km), using stable isotope analysis of δ13C and δ15N, in a
lacustrine reach of the Saint John River receiving point-source anthropogenic
inputs. Relative movements of five common fish species were analyzed using
discriminant analysis of the stable isotopic signatures (Litvin & Weinstein 2004,
Harrod et al. 2005). Brown bullhead (Ameirus nebulosus) and white sucker
(Catostomus commersoni) are moderately large-bodied benthic generalists,
75 banded killifish (Fundulus diaphanus) are small-bodied-littoral generalists, while
white perch (Morone americana) and yellow perch (Perca flavescens) are pelagic
and littoral omnivores, respectively (Scott and Crossman 1973)
We sampled fish from sites located both upstream and downstream, and
on the far-bank, from a pulp mill effluent (PME) discharge. Since PME can affect
fish condition fact, the condition of the fish was analyzed to determine what, if
any, effect the PME had on the fish, since this would also confirm exposure to
the effluent. Since the depth (>25 m) and width (~1 km) of the river may provide a barrier to smaller and benthic fish species, we hypothesize that these species
will show less cross-river movement than larger and pelagic species.
3.3 Methods
3.3.1 Study Site
Mactaquac Lake is an impoundment of the Saint John River formed by the
creation of the Mactaquac hydroelectric dam in 1968 upstream of Fredericton,
NB. Maximum depth of the lacustrine reach reaches approximately 25 m, and width ranges from 500 m to 1 km. The town of Nackawic is located at the upper lacustrine reach of the system, approximately 60 km upstream from the dam.
The pulp mill at Nackawic is a bleached-kraft hardwood mill which produces high quality pulp used to make photographic paper. The mill’s effluent is treated in several lagoons, and is released into the lake by an offshore multi-port diffuser.
76 Ten sites were sampled, located upstream, downstream, and across the river
from the mill’s effluent discharge (Table 3, Figure 8).
3.3.2 Fish Sampling
Sampling took place from 16 to 25 June 2003 and 14 to 25 June 2004. To
catch fish of different sizes and habits we employed a variety of sampling
methods at all sites, except where otherwise noted. One trap-net with a 30 m
lead and ~5 cm mesh size were deployed in 3-5 m of water, and retrieved the
following morning after approximately 24 hours. Trap nets were not set at sites
FB1 or STP, due to steep drop-offs and lack of suitable habitat. Gangs of four
gillnets (22 m, mesh 2.2 cm – 10 cm) were set for three repetitions of 30 minutes.
Ten minnow traps and one Windermere trap were set overnight and retrieved
after approximately 24 hours. Beach seines (30 m), with a mesh size of
approximately 1cm, were used to seine approximately 50m of shore. Site FB1
was not seined due to steep drop-offs. Boat electrofishing was used at some sites to collect samples for SIA.
Target fishes were identified to species: banded killifish (Fundulus diaphanus), brown bullhead (Ameirus nebulosus), white perch (Morone americana), white sucker (Catostomus commersoni), and yellow perch (Perca flavescens). Due to ontogenetic dietary shifts in white perch and yellow perch, only individual white perch longer than 14 cm, and yellow perch longer than 12 cm, were analysed for stable isotopes. Lengths and weights (to the nearest 1.0
77 mm and 0.1 g respectively) were recorded from the first 25 fish sampled. These
were used to calculate Fulton’s condition index, K, using the formula
(1) K = 100 x (W / L3)
where W is fish weight in g, and L is length of the fish in cm.
Three adult individuals of each target species were sampled for stable
isotope analysis. Fish were sacrificed in the field, and samples of dorsal white muscle tissue were excised from larger bodied fish, while whole smaller fish were retained for analysis. Samples were placed on ice in the field and kept frozen in
the lab until preparation. At this time, smaller fish were eviscerated, skinned, de-
finned, and decapitated. All fish not utilized for stable isotope analysis were
released. All research was approved by the University of New Brunswick Animal
Care Protocol Committee and was conducted under a Canadian Department of
Fisheries and Oceans Sampling permit.
3.3.3 Stable Isotope Sample Preparation
Samples were placed into 7 ml or 20 ml glass scintillation vials, and dried
in a drying oven for 48 h at 60o C. They were then ground to a fine powder using
pestle and mortar. All implements were disinfected using acetone between
samples. Samples were weighed into 0.2 mg (± 10 %) aliquots, placed into 5
mm x 3.5 mm tin capsules, and analyzed for δ13C and δ15N using either a
78 Thermo-Finnigan Delta Plus or Delta XP isotope-ratio mass spectrometer interfaced with a Carlo Erba NC2500 Elemental Analyzer via the Conflo II or
Conflo III, respectively. δ15N and δ13C are determined from the same sample, and are calculated using the formula:
(2) δX = [(Rsample/Rstandard)-1] x 1000
where X refers to the rare, heavy isotope, and R is the ratio of the heavy isotope
(15N, 13C) to the light isotope (14N, 12C) in the sample and in a standard. The
standard for nitrogen is atmospheric nitrogen (AIR), and for carbon is carbon
dioxide derived from calcium carbonate in the Pee Dee Bee formation of South
Carolina (PDB). Approximately one sample in 15 was sub-sampled and
analyzed twice. Additionally, a personal standard (yellow perch from Nackawic)
was analyzed in every run to test for variation.
Four International Atomic Energy Agency standards (N1, N2, CH6 and CH7)
and three elemental standards (Acetanilide, Cyclohexanone, and Nicotinamide)
were used throughout each run. The standard deviation for the personal
standard was 0.09 for δ13C and 0.17 for δ15N. The standard deviations for
isotopic standards ranged from 0.07 to 0.17 for δ13C and 0.07 to 0.26 for δ15N;
and for elemental standards ranged from 0.04 to 0.29 for δ13C and 0.08 to 0.23
for δ15N.
79 3.3.4 Data Analysis
Discriminant analysis was performed on the stable isotope signatures of each of the fish species to determine what proportion of individuals captured at each site could be correctly assigned to that site, and from which movements among sites could be extrapolated. If the individual was assigned to its site of capture it was deemed to be resident, while if it was assigned to another site, it was assumed that it was a migrant from that site. To increase relative sample size, fishes were pooled according to whether they were from downstream (DS), upstream (US), or far-bank (FB) sites, and analyzed according to “site type.”
Analysis therefore tested for movements between “site-types” rather than between individual sites. Gaussian bivariate plots of δ13C and δ15N were
analyzed using the ELM function, which is analogous to the standard error, and
calculates a bivariate confidence interval in the form of an ellipse around the
centroid of the mean. Condition factor (K) was analyzed using ANOVA, and a posthoc Tukey pairwise comparison was used to test for differences among unpooled sites. All statistical analysis was performed using SYSTAT 10.2 (SPSS
Inc., Chicago Il., U.S.A.).
3.4 Results
3.4.1 How Much do the Fishes Move?
Discriminant analysis revealed that most banded killifish (62%, p<0.005)
were assigned to their site of capture (Table 4). Incorrect assignments suggest
80 that there is some movement across the river, but relatively little upstream or
downstream movement. No DS killifish were assigned to US sites. Low variation
in δ15N values (Figures 9, 10) suggest that banded killifish may not be exposed to
the effluent. Brown bullhead show some movement across the river, but
relatively little movement upstream or downstream (Figures 9, 10). Only 58%
were correctly assigned to their capture site (p<0.05), but there appears to be
some cross-bank movement (Table 4). The bivariate plot for white suckers
shows that US suckers overlap with both DS and FB, but there appears to be
separation between FB and DS sites (Figures 9, 10). While 70% of white suckers from DS sites were correctly assigned, and none to FB sites, just 58%
(p=0.6) were correctly assigned overall (Table 4).
The majority of white perch were incorrectly assigned to their sites, and
FB sites showed the greatest fidelity with 56% of the fish correctly assigned
(Table 4). Overall, only 32% (p=0.7) of white perch were correctly assigned.
There are no discernable patterns in the distribution of signatures for white perch,
as they show tremendous variation in δ15N signatures across sites (Figures 9,
10). The bivariate ellipses for yellow perch (Figures 9, 10) suggest that the FB and DS sites are distinct from one another. This is supported by 87% of yellow perch caught at the DS sites being classified to their capture site (p<0.0005),
while none were assigned to upstream sites and just 16% were incorrectly
assigned between FB and DS (Table 4). However, many fish from US were
assigned to FB and DS.
81 3.4.2 Is Fish Condition Affected Near the PME Discharge?
Banded killifish condition (ANOVA, p<0.05) revealed no significant differences among sites, although condition was lowest at DS sites and STP, and was highest at US2 and US3 (Figure 11). Brown bullhead condition (ANOVA, p<0.0005) was highest at DS1-4 and was lowest at FB1 (Figure 11), with significant differences (Tukey <0.05) between DS1 and US1, US3. White perch condition (ANOVA, p<0.0005) was highest at FB2, and lowest at STP and US1
(Figure 11). There were significant differences (Tukey <0.05) between FB2 and
FB3, NS, US1, and between US1 and US2-3. White sucker condition (ANOVA, p<0.05) was highest at DS3, DS4, and FB1, and was lowest at NS and STP
(Figure 11), with a significant difference between DS4 and NS (Tukey p<0.05).
Yellow perch condition (ANOVA, p<0.000005) was highest at DS2 and was lowest at STP (Figure 11). Site DS2 was significantly different (Tukey p<0.05) from every site other than DS4, while STP was also significantly different from
US2, US3, and FB2.
3.5 Discussion
3.5.1 How much do the fish move?
Banded killifish appear to move both up- and downstream and across the river to a limited, but greater than expected, extent. The lower-than-expected site fidelity may be due to lack of exposure to the effluent, as killifish feed on a variety of small invertebrates in the inshore/littoral area, and I have shown in
82 chapter 2 that PME does not appear to affect this species. They school in quiet areas, over sand, gravel, or detritus where there are submerged aquatic plants.
They are multiple spawners and do not migrate to spawn (Scott & Crossman
1973, Becker 1983). As such, the model may be overestimating killifish movement due to lack of differentiation in isotopic signature resulting from lack of exposure to the effluent rather than being indicative of large-scale movement.
Skinner et al. (in press) found a leptokurtic distribution of movement in closely related mummichog (Fundulus heteroclitus) wherein the majority of fish did not move, but a small minority showed large-scale movements of several kilometres.
This distribution has also been found in other species of killifish (Fraser et al.
2001), so banded killifish may well have similar movement patterns.
Brown bullhead appear to have moderate amounts of movement across the river, although we would have expected less across-river movement and more up- or downstream movement due to their benthic habits. It has been shown that while they tend to move along the shore, they may have a net displacement of almost 1000 m and a total distance travelled of up to 5 500 m over several hours in Lake Ontario (Kelso 1974). A mark-recapture study in
Folsom Lake, California found that brown bullhead moved an average of 2.7 km and a maximum of 26.1 km before being recaptured (Emig 1966, cited in Becker
1983). They prefer warmer and shallower water, with vegetation and sand-mud substrates, but they are very tolerant to a wide range of environmental factors such as temperature, oxygen and pollution (Scott & Crossman 1973, Becker
1983). In Lake Taupo, New Zealand, they may be found as deep as 22 m, but
83 tend to prefer vegetated areas and so depth may be limited to an extent by the
depth profile of aquatic vegetation (Dedual 2002). Generalist omnivores, they
are considered to feed at or near the bottom, although Dedual (2002) found that they used the upper 2-4 m of the water column while foraging at night. They
construct nests to spawn, and are not known to migrate long distances (Scott &
Crossman 1973).
White sucker show mostly up- and downstream movement, with relatively little cross-river movement, which we would expect since they tend to prefer shallow areas within lakes, although older and larger fish may be found in deeper
water (Scott & Crossman 1973, Becker 1983). Kelso (1976) found that non- spawning white sucker in Lake Erie, Ontario, travelled of up to almost 4 000 m over the course of several hours, with a net displacement of up to approximately
700 m. In South Bay, Lake Huron, white suckers moved on average 0.6-12.9 km
from the tagging site, while one moved 56 km before being caught 5 years later
(Coble 1967, cited in Becker 1983). There was high variability amongst the white sucker, as evidenced by the high p-value which may be due to the time of sampling, since white sucker are known to make a vernal spawning migration from the main branch into smaller tributaries. While studies have revealed that they generally do return to their locale of origin (Doherty et al. In Press), this has
not been investigated at the scale of this project. At the time of sampling (two to four weeks after spawning), white sucker may either not yet have returned to their sites of origin, or may have settled at other sites. As a result, they may not have had time to assimilate new isotopic signatures (Hesslein et al. 1993). That
84 the majority of individuals were correctly assigned suggests that they do tend to
show fairly high site fidelity when returning post-spawning. White sucker show
high variation in δ13C values and are generalist benthic feeders, so the wide
range of prey taken may account for some of the variation and difficulty in placing
fish.
White perch appear to show very low site fidelity, and move both across
the river as well as up- and downstream. The river does not appear to provide a
barrier to white perch movement. This may be expected due to their habits – the
δ13C isotopic signature of white perch suggests that they feed almost entirely in
the pelagic food web, while the other fish studied show more of a littoral
influence. As a facultative anadromous species which frequently inhabits large
water bodies and estuaries they may be a stronger swimming species than the others studied. They feed primarily at night when they move inshore and to the surface in schools, while they tend to be found in deeper water during the day.
As white perch grow, they undergo an ontogenetic dietary shift, from plankton to aquatic insect larvae to piscivory. The dietary shift from invertebrates appears to occur around 15-20 cm FL, although at almost any size a range of prey will be taken (Scott & Crossman 1973, Becker 1983). Although we sampled fish of a relatively constant size for the stable isotopic analysis, variation in the signatures
suggests that individual variation in feeding habits and timing of the ontogenetic
shift may confound the analysis.
Yellow perch showed very little cross-river movement, and no upstream
movement, although there was some downstream movement. This is not
85 surprising since they are considered a shallow-water species, although they will
undergo diel and seasonal movements inshore-offshore, and vertically in the water column in response to temperature and food (Scott & Crossman 1973,
Becker 1983). Kelso (1976) found that yellow perch in Lake Erie, Ontario, travel up to 1800 m in several hours, with a net displacement of up to approximately 1
000 m. A tagging study in Green Bay, WI, revealed that while most yellow perch remained in the tagging area, approximately 27.8% moved distances up to 81 km
(Mraz 1951, cited in Becker 1983). These movements did not appear to be
spawning-related. They prefer areas with significant vegetation, and their diet
consists primarily of invertebrates at smaller sizes, but shifts to a more
piscivorous diet as the fish grows, with the dietary shift being manifest at around
15 cm in length (Scott & Crossman 1973, Becker 1983). As with the white perch,
individual variation in this ontogenetic shift may confound the analysis.
3.5.2 Are the fish affected by PME?
During Canada’s Environmental Effects Monitoring (EEM) program, fishes exposed to PME were commonly found to have high condition factors relative to
fishes from non-impacted sites at most locations (Lowell et al. 2003). Positively
correlated with other biologically significant parameters such as liver weight and
weight-at-age, these changes are thought to be indicative of nutrient enrichment
(Lowell et al. 2003), and suggest that the PME is affecting the fish at many sites.
The EEM report indicated a trend towards increased weight and condition in both
white sucker and yellow perch from exposed sites (Lowell et al. 2003).
86 Nutrient enrichment can be manifest in higher condition factor, which is
supported by these findings of higher condition factor at DS sites in yellow perch,
brown bullhead and white sucker. DS2 yellow perch have high relative δ15N values, suggesting that they may feed at a higher trophic level than yellow perch at other sites. White sucker and brown bullhead from DS4 have the highest condition, suggesting that while yellow perch may benefit from nutrient enrichment immediately downstream of the effluent, the food of brown bullhead and white sucker is enriched further downstream.
3.5.3 Conclusions
Based on this study, white perch are a cosmopolitan species, moving a great deal among sites, both up- and down-stream, while yellow perch showed high site-fidelity and little movement among sites. Banded killifish, brown bullhead, and white sucker showed intermediate inter-sites movements, although in the case of banded killifish this may result from a lack of differentiation among isotope signatures due to exposure to the effluent rather than large-scale movements. Brown bullhead and white sucker are both moderately large
benthivorous species, and their movements may be limited by the depth of the
river and anoxic conditions in the hypolimnion.
It is important to note that the absence of differences in stable isotopic
signatures among fish at different sites does not necessarily indicate that the sites are interconnected, but may signify lack of exposure to effluent, or a reliance on similar food sources. If differences are seen among stable isotope
87 signatures, however, then this suggests that there is little or no movement between the sites. Individual specialization is a potentially confounding factor in these analyses, as differences in isotopic signatures may be driven more by variation in individual feeding habits rather than inter-site differences. However, since this study has shown differences in the signatures of yellow perch, white sucker and brown bullhead among sites, this is unlikely to be a major problem in these species. The lack of variation among signatures in banded killifish suggests that this is not an issue in this species either. There are some individuals from each species which have signatures suggestive of feeding on a different food source (Figure 9), but these probable specialists are in the minority and most individuals seem to be generalists. My results show that stable isotope analysis, when analyzed using discriminant analysis, is able to successfully identify small-scale fish movements when pulp mill effluent is used as a stable isotopic tracer. Since these results can also be used to trace energy and nutrient flows through trophic dynamics, and as such make stable isotope analysis a versatile technique.
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94 Table 3. Fish community and stable isotope sampling sites, with site name,
abbreviation, and location.
Site Site Name Location abbreviation DS1 Downstream 1 200 m DS of PME discharge DS2 Downstream 2 1000 m DS of PME discharge DS3 Downstream 3 2300 m DS of PME discharge DS4 Downstream 4 5000 m DS of PME discharge FB1 Far Bank 1 1000 m US, in riverine reach FB2 Far Bank 2 500 m DS FB3 Far Bank 3 2500 m DS US1 Upstream 1 2500 m US, in riverine reach US2 Upstream 2 1000 m US, across bay US3 Upstream 3 1000 m US
95 Table 4. Percentage of each species classified to each site-type using
discriminant analysis. Bold denotes the percentage correctly assigned.
Species Site of n Assigned Site Capture DS (%) FB (%) US (%)
Banded Killifish DS 11 55 27 18
FB 7 29 57 14
US 8 0 38 63
Brown Bullhead DS 11 45 36 18
FB 4 25 50 25
US 9 11 11 78
White Perch DS 14 29 43 29
FB 9 33 56 11
US 11 36 45 18
White Sucker DS 10 70 0 30
FB 8 25 50 25
US 8 25 25 50
Yellow Perch DS 15 87 13 0
FB 16 19 75 6
US 15 40 33 27
96 N PEI DS4 NS NB * QC ME Mactaquac Lake Saint John River N DS3 1 000 1 000 m FB3 DS2 ME” denotes pulp mill effluent outfall. DS1 ctaquac Lake, NB. US: upstream sites, DS: downstream sites, FB: far-bank upstream sites, DS: ctaquac Lake, NB. US: FB2 Pulp Mill PME US3 US2 FB1 US1 sites. Solid circle with caption “P Nackawic Figure 8: Map of study sites in Ma
97
Figure 9: Line graphs of mean δ13C and δ15N (± SE) for baselines (mussels and
snails) and five common fish species from sites in Mactaquac Lake, NB.
98 -18 9.0 Snails SE Snails SE
8.5 -20
8.0 -22
7.5 d15N d13C -24 7.0
-26 6.5
-28 6.0 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP
-30.0 11.0 Mussels SE Mussels SE 10.5 -30.5
10.0 -31.0
9.5 -31.5 d13C d15N 9.0
-32.0 8.5
-32.5 8.0
-33.0 7.5 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP
-22 12.8 Banded Killifish, SE Banded Killifish, SE 12.6 -23 12.4
12.2 -24 12.0
-25 11.8 d13C d15N 11.6 -26 11.4
11.2 -27 11.0
-28 10.8 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP
-24 13 Brown Bullhead SE Brown Bullhead SE -26 12
-28 11
-30 10 d13C d15N -32
9 -34
8 -36
-38 7 US1 US2 US3 DS1 DS2 DS3 DS4 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB2 FB3 NS STP
99 -24 15 White Perch >14cm SE White Perch >14cm SE 14 -26
13 -28
12 -30 d13C d15N 11
-32 10
-34 9
-36 8 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS
-22 13 White Sucker SE White Sucker SE -24 12
11 -26
10 -28 9 d13C -30 d15N 8
-32 7
-34 6
-36 5 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP
-20 16 Yellow Perch >12cm SE Yellow Perch >12cm SE -22 15
-24 14
-26 13 -28 12 d13C -30 d15N 11 -32
10 -34
-36 9
-38 8 US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP US1 US2 US3 DS1 DS2 DS3 DS4 FB1 FB2 FB3 NS STP Site Site
100
Figure 10: Scatter plots of stable isotope data, with ELM bivariate ellipses (solid
line – DS sites, dashed – FB, dotted – US) for data points grouped
according to site type for (a) banded killifish, (b) brown bullhead, (c)
white sucker, (d) white perch, and (e) yellow perch. ELM bivariate
ellipses represent an estimate of the standard error of the mean for all
data points of that type.
101 13
12
N 15 δ
11 SITE TYPE DS FB 10 US -27 -26 -25 -24 -23 -22 δ13C
Banded Killifish
13
11
N 15 δ
9 SITE TYPE DS FB 7 US -34 -32 -30 -28 -26 -24 δ13C
Brown Bullhead
102 13
12
11
N
15 10 δ
9
8 SITE TYPE 7 DS FB 6 US -34 -32 -30 -28 -26 -24 δ13C
White Sucker
15
14
13
N 12 15 δ 11
10 SITE TYPE 9 DS FB 8 US -34 -32 -30 -28 -26 -24 δ13C
White Perch
103
16
14
N 12 15 δ
10 SITE TYPE DS FB 8 US -32 -30 -28 -26 -24 -22 δ13C
Yellow Perch
.
104 1.2 Banded Killifish 1.1
1.0
0.9
Condition (K) Condition 0.8
0.7
0.6
S2 S3 S4 B3 NS US1 U US3 DS1 DS2 D D FB1 FB2 F STP 1.7 Brown Bullhead
1.6
1.5 Condition (K) Condition 1.4
1.3 1 S S3 S1 S3 S4 B2 NS U US2 U D DS2 D D FB1 F FB3 STP 1.5 White Sucker
1.4
1.3 Condition (K) Condition 1.2
1.1 1 2 3 2 3 4 2 S S S B3 N U US US DS1 D DS DS FB1 FB F STP 1.6 White Perch
1.5
1.4 Condition (K) Condition 1.3
1.2 P S2 S3 S2 S3 S4 B1 NS T US1 U U DS1 D D D F FB2 FB3 S 1.6 Yellow Perch 1.5
1.4 Figure 11: Fulton’s condition factor (K)
1.3 for five common fish species
Condition (K) Condition 1.2
1.1 in Mactaquac Lake, NB.
1.0 1 P S2 S2 B1 B2 NS US U US3 DS1 D DS3 DS4 F F FB3 ST
105 4 GENERAL DISCUSSION
Fish populations integrate the effects of stressors associated with their
environment directly through changes to the fishes’ condition, reproductive
fitness, and health; or indirectly by affecting predators, prey, competitors, and parasites (Valtonen et al. 1997). Many environmental monitoring programs rely on surveys of sentinel species, comparing physiological parameters (such as relative gonad weight, liver weight, and condition) between impacted and reference sites (Munkittrick et al. 2000). An ideal reference site should be located in close proximity, and therefore be subject to the same environmental variables, as the impacted site, but be spatially isolated in terms of fish movements.
One major assumption of these studies is that the individual fish have been exposed to the contaminant, and are resident in the impacted area.
Likewise, it is assumed that fish at the reference site have not been exposed to the stressor of interest. There are a number of challenges to developing a good monitoring program, and typical problems encountered include inadequate reference sites, the presence of confounding discharges, and mobility of fish between reference and exposure sites (Munkittrick et al., 2002).
Concerns were raised that the reference site selected for the Cycle 1 and
Cycle 2 Environmental Effects Monitoring (EEM) programs at Nackawic was not appropriate for several reasons. The Beechwood reservoir was chosen because it is a large reservoir on the Saint John River, is geographically separated from
106 Nackawic, and both sentinel species (white sucker and yellow perch) are present
(BEAK 1996, 2000). However, it is approximately 120 km upstream from
Nackawic, has different hydrodynamic properties, different confounding discharges, and different fish community composition (Stantec 2004). Many of the physiological parameters measured during the Cycle 1 and 2 programs at
Nackawic revealed opposite trends from what would have been expected based the results from programs at other locations (BEAK 1996, 2000, Lowell et al.
2003, Munkittrick et al. 2002) and it was unclear whether these results were due to the pulp mill effluent, or to other environmental factors. It was therefore decided to attempt to identify local reference sites for future cycles of the EEM program. In addition, the town of Nackawic’s municipal waste water discharge is in close proximity (~1.5 km upstream on the opposite bank of the river), resulting in another potentially confounding effect.
The primary objectives of this thesis were to examine fish community responses to pulp mill and municipal sewage effluent, and to ascertain fish movement patterns and site fidelity. These two objectives were largely to be described using stable isotope analysis, and the utility of this technique to these questions was also to be determined. Finally, the applications of these results to environmental monitoring studies were to be described.
4.1 Integration and Applications of Findings
Fish species richness, abundance, and diversity appear to be negatively correlated with pulp mill effluent - cyprinids (minnows) were virtually absent from
107 impacted sites, while white perch were ubiquitous and did not appear to be affected by the effluent. Nutrient enrichment appears to be manifest, in part, by altering the trophic positions and littoral-pelagic balance of food sources of many species, notably yellow perch whose condition is also higher at downstream sites.
Baseline isotopic signatures reveal that the pelagic food web is impacted more than the littoral, which suggests that the pulp mill effluent plume does not reach the bank. This is supported by the lack of a clear isotopic signal from pulp mill effluent in littoral species such as banded killifish, whose condition also does not appear to be affected at downstream sites. Pulp mill effluent is an effective tracer of fish movements due to its distinct stable isotopic signal, and is not noticeably confounded by upstream anthropogenic inputs.
While the analysis in many stable isotope studies is primarily descriptive and qualitative, the use of multivariate statistics to analyze isotopic data quantitatively is increasing. Recent studies have used discriminant analysis to determine post-movement settlement patterns of juvenile weakfish (Cynoscion regalis) in marine estuaries (Litvin & Weinstein 2004) and movement patterns of
European eels (Anguilla anguilla) between marine and freshwater (Harrod et al.
2005). This technique has not been applied to studies within freshwater systems due, in part, to the small isotopic differences among habitats compared to the differences between marine and freshwater. However, despite the small sample sizes in this study, discriminant analysis proved effective at determining site-
108 fidelity and movements of fishes when some sites are exposed to anthropogenic inputs.
4.2 Applications to environmental monitoring studies
A variety of methods have been used to assess the impact of effluents on the aquatic environment. Those dealing with fish have generally either assessed changes at the individual level (sentinel species approach) or the community level (Kovacs et al. 2002). At the individual level, studies have traditionally dealt with physical factors such as overall condition, relative gonad size, and reproductive condition (Munkittrick et al. 2000, Galloway et al. 2003, Lowell et al.
2003); and biochemical factors such as hepatic mixed function oxidase and plasma steroid levels in one or two locally abundant sentinel species (Munkittrick et al. 2000, Kovacs et al. 2002). While we can assess the effects of anthropogenic activities on individual fishes and fish populations, this information may have more ecological relevance when put into the larger context of the community (Kovacs et al. 2002). Many community studies use a combination of species richness, abundance (often standardized as catch-per-unit-effort), and diversity indices to measure the community structure and to compare differences among sites. These approaches may collapse information into a single number, such as Indices of Biotic Integrity (Mebane et al. 2003, Kovacs et al. 2002,
Hughes et al. 2004).
My findings suggest that yellow perch would be best suited as a sentinel species for future environmental monitoring studies at this site, since they show
109 limited movement, and appear to be influenced by the PME at the exposed sites
(Table 5). Yellow perch have been used as a sentinel species at this site in past monitoring programs (Table 5, BEAK 1996, BEAK 2000, Stantec 2004), but were compared with distant and possibly unsuitable reference sites. The use of a far- bank reference for this species in future surveys is supported by my findings.
There is a current trend in Environmental Effects Monitoring studies towards small-bodies fish species (Galloway et al. 2003, Lowell et al. 2003, Gray et al.
2004). Since banded killifish show limited movement patterns and are small bodied, they would appear to be a good candidate for further studies. The closely-related mummichog (Fundulus heteroclitus), is an estuarine species that is widely used in EEM studies and this species has been shown to have limited movements and show physiological responses to PME (Skinner 2005).
However, this study has shown that banded killifish are either not exposed, or are not affected by the pulp mill effluent at this site.
White perch have extensive movements, and so may not be a suitable sentinel species. White sucker, which have been used in previous monitoring studies at this site (Table 5, BEAK 1996, Stantec 2004), and widely across
Canada (Lowell et al. 2003), are confounded at this site by their annual vernal spawning migration to smaller tributaries, but probably show high site fidelity outside of that migration and may be a suitable sentinel species (Doherty 2004).
EEM studies at this site showed differences in most physiological parameters between the exposure and reference sites, so they are impacted by exposure to the PME upon return from the spawning migration (Table 5). If cross-river
110 movements are minimal, a far-bank reference site would be suitable for this
species at this site. Brown bullhead appear to move too much, and assessing
reproductive health in this species may be complicated by the males making and
guarding nests, so standard methodologies for assessing reproductive effort may
not work well.
The use of local reference sites is supported here for some species. A
far-bank reference site would appear to be suitable for environmental monitoring
using brown bullhead, white sucker or yellow perch, while an upstream reference
site would be more suitable for banded killifish. While most of these results can
only be directly applied to this study site, the methodologies and general
framework therein may be applicable, in part, to similar studies at other sites.
Additionally, these results will add to our general knowledge of the movement
patterns of specific fish species, to the effects of anthropogenic inputs and
nutrient enrichment on fish communities, and to the application of stable isotope analysis in ecological studies.
4.3 Conclusions and Suggestions for Future Research
This project comprised both general and applied research, and these are the key
findings and suggestions for future research from this thesis:
• Fish community structure and trophic dynamics are affected by pulp mill
effluent and municipal wastewater, with lower species richness, diversity
and abundance;
111 • Several species, such as yellow perch, feed at higher trophic positions
and on a higher proportion of littoral resources at sites downstream from
the pulp mill effluent discharge;
• Movement patterns suggest that adult yellow perch (>12cm)show high
site-fidelity and are the best option as a sentinel species. White sucker
are probably the best choice for a second sentinel species;
• Ecological studies, including those involving stable isotope analysis,
investigating fish species which undergo trophic ontogeny (such as yellow
perch and white perch) must factor these dietary shifts into the analysis;
• For future Environmental Effects Monitoring studies at Nackawic, the
researchers should consider using reference sites located on the far-bank
from the exposure sites;
• While the conclusions with regards to environmental monitoring studies
stemming from this thesis can only apply directly to studies at the pulp mill
at Nackawic, they should be taken into consideration when planning
studies at other sites as the general principles and findings of this project
would likely prove applicable; and
• Stable isotopes are a useful tool for ecological studies; providing added
resolution for community studies and helping to discern movement
patterns when point-source inputs are used as markers. Multivariate
analyses, where appropriate, can and should be used to analyze such
data.
112 4.4 Literature Cited
BEAK. 1996. Cycle 1 EEM final interpretative report for St. Anne-Nackawic Pulp
Company Limited, Nackawic, New Brunswick. Beak International
Incorporated, Brampton, ON.
BEAK. 2000. Second Cycle EEM final interpretative report for St. Anne-Nackawic
Pulp Company Limited, Nackawic, New Brunswick. Beak International
Incorporated, Brampton, ON.
Doherty, C.A. 2004. Movement patterns and biology of white sucker in a riverine
environment exposed to multiple stressors. M.Sc. Thesis, University of New
Brunswick, Fredericton, NB. 100 pp.
Galloway, B.J., K.R. Munkittrick, S. Currie, M.A. Gray, R.A. Curry & C.S. Wood.
2003. Examination of the responses of slimy sculpin (Cottus cognatus) and
white sucker (Catostomus commersoni) collected on the Saint John River
(Canada) downstream of pulp mill, paper mill, and sewage discharges.
Environmental Toxicology and Chemistry 12: 2898-2907.
Gray, M.A., R.A. Cunjak & K.R. Munkittrick. 2004. Site fidelity of slimy sculpin
(Cottus cognatus): insights from stable carbon and nitrogen analysis.
Canadian Journal of Fisheries and Aquatic Sciences 61: 1717-1722.
Harrod, C., J. Grey, T.K. McCarthy & M. Morrissey. 2005? Stable isotope
analyses provide new insights into ecological plasticity in a mixohaline
population of European eel. Oecologia 144: 673-683.
113 Hughes, R.M., S. Howlin & P.R. Kaufmann. 2004. A biointegrity index (IBI) for
coldwater streams of western Oregon and Washington. Transactions of the
American Fisheries Society 133: 1497-1515.
Kovacs, T.G., P.H. Martel & R.H. Voss. 2002. Assessing the biological status of
fish in a river receiving pulp and paper mill effluents. Environmental Pollution
118: 123-140.
Litvin, S.Y. & M.P. Weinstein. 2004. Multivariate analysis of stable-isotope ratios
to infer movements and utilization of estuarine organic matter by juvenile
weakfish (Cynoscion regalis). Canadian Journal of Fisheries and Aquatic
Sciences 61: 1851-1861.
Lowell, R.B., S.C. Ribey, I.K. Ellis, E.L. Porter, J.M. Culp, L.C. Grapentine, M.E.
McMaster, K.R. Munkittrick & R.P. Scroggins. 2003. National assessment of
the pulp and paper environmental effects monitoring data. NWRI Contribution
No. 03-521, 143 pp.
Mebane, C.A., T.R. Maret & R.M. Hughes. 2003. An Index of Biological Integrity
(IBI) for Pacific northwest rivers. Transactions of the American Fisheries
Society 132: 239-261.
Munkittrick K.R., S.A. McGeachy, M.E. McMaster, S.C. Courtenay. 2002.
Overview of freshwater fish studies from the pulp and paper environmental
effects monitoring program. Water Quality Research Journal of Canada 37:
49-77.
Munkittrick, K.R., M.E. McMaster, G. Van Der Kraak, C. Portt, W.N. Gibbons, A.
Farwell & M. Gray. 2000. Development of methods for effects-driven
114 cumulative effects assessment using fish populations: Moose River Project.
Society of Environmental Toxicology and Chemistry (SETAC). 256 pp.
Skinner, M.A. 2005. The site fidelity of mummuchogs (Fundulus heteroclitus) in
an Atlantic Canadian estuary: implications for use as a sentinel species in
environmental monitoring. M.Sc. Thesis, University of New Brunswick,
Fredericton, NB. 121 pp.
Stantec. 2004. Cycle 3 Environmental Effects Monitoring interpretive report for
St. Anne-Nackawic Pulp Company Ltd., Nackawic, New Brunswick. Stantec
Consulting Ltd., Brampton, ON. 162 pp.
Valtonen, E.T., J.C. Holmes & M. Koskivaara. 1997. Eutrophication, pollution,
and fragmentation: effects on parasite communities in roach (Rutilus rutilus)
and perch (Perca fluviatis) in four lakes in central Finland. Canadian Journal
of Fisheries and Aquatic Sciences 54: 572-585.
115 Table 5: Comparison of Environmental Effects Monitoring endpoints in white sucker (Catostomus commersoni) and yellow
perch (Perca flavescens) from the Cycle 3 Adult Fish Survey at Nackawic, Mactaquac Lake, NB.
Fork Total Gonad Liver # Eggs/ Length Weight Weight Weight Condition Total Egg Adjusted Sex Site Value (cm) (g) (g) (g) GSI LSI (K) Eggs weight (g) Total Weight
Female Exposure Mean 41.61 941.92 47.71 13.10 5.37 1.40 1.29 21164.91 2.328E-03 23.42284 SE 77.64 10.09 3.94 1.240.40 0.11 3457.30 5.784E-04 3.66997 n 23 23 23 20 23 20 23 23 23 23
Female Reference Mean 30.25 321.73 10.52 3.67 3.40 1.15 1.13 7126.32 1.486E-03 23.85627 SE 26.98 2.82 0.69 0.700.18 0.06 1700.11 3.491E-04 5.062889 n 22 22 22 22 22 22 22 22 22 22
Male Exposure Mean 36.05 644.99 39.61 7.66 6.45 1.27 1.33 SE 71.89 7.12 1.91 0.860.24 0.11 n 22 22 22 19 22 19 22
Male Reference Mean 27.44 241.92 10.85 2.04 4.71 0.84 1.15 SE 13.79 1.64 0.30 0.730.14 0.07 n 9 9 9 9 9 9 9
116 Yellow Perch:
Fork Total Gonad Liver # Eggs/ Length Weight Weight Weight Condition Total Egg Adjusted Sex Site Value (cm) (g) (g) (g) GSI LSI (K) Eggs weight (g) Total Weight
Female Exposure Mean 17.61 60.26 3.79 1.00 6.95 1.80 1.07 9857.98 3.971E-04 177.3992 SE 15.35 1.42 0.41 3.811.10 0.37 3292.66 1.058E-04 67.32916 n 30 30 30 30 30 30 30 28 28 28
Female Reference Mean 20.52 98.95 5.99 1.20 6.51 1.24 1.10 16755.61 3.982E-04 178.2567 SE 10.13 2.26 0.27 2.320.20 0.10 7575.19 1.728E-04 60.81168 n 22 22 22 22 22 22 22 22 22 22
Male Exposure Mean 14.72 39.00 2.50 0.39 7.23 0.89 1.09 SE 8.56 0.57 0.11 1.690.32 0.11 n 6 6 6 6 6 6 6
Male Reference Mean 17.39 61.19 3.90 0.50 6.80 0.81 1.16 SE 3.42 0.66 0.16 1.130.24 0.07 n 7 7 7 7 7 7 7
117 Curriculum Vitae
Jonathan Adam Freedman
Universities Attended:
2001 B.Sc. (Honours Zoology), University of Guelph
Publications in Refereed Journals:
Freedman, J.A. & D.L.G Noakes. 2002. Why are there no really big bony fishes? A point-of-view on maximum body size in teleosts and elasmobranchs. Reviews in Fish Biology and Fisheries. 12: 403-416.
Conference Presentations, Posters, & Invited Seminars:
Freedman, J.A. 2005. Assessing fish communities: integration of stable isotope analysis and traditional methodologies. Poster. Annual Meeting of the American Fisheries Society. September 11-15, Anchorage AK.
Freedman, J.A. 2005. Determining movements and trophic dynamics of fishes: a stable isotope approach; or, How I learned to stop worrying and love stable isotopes. Invited Seminar. Queen Mary, University of London. May 24, London UK.
Freedman, J.A., R.A. Curry, K.R. Munkittrick, W.R. Parker & E. Blair. 2004. Determining the effects of pulp mill effluent on fish communities using stable isotope analysis. Annual Meeting of the American Fisheries Society. August 22-26, Madison WI.
Freedman, J.A., C.A. Doherty, R.A. Curry, K.R. Munkittrick, W.R. Parker & E. Blair. 2004. Effects of pulp mill effluent on fish communities. Poster. Canadian Water Network - National Symposium. June 20-22, Ottawa ON.
Freedman, J.A., R.A. Curry, K.R. Munkittrick, W.R. Parker & E. Blair. 2004. Effects of pulp mill effluent on fish communities. Annual Meeting of the Canadian Society of Zoologists. May 11-15, Wolfville NS.
Freedman, J.A., C.A. Doherty, R.A. Curry, K.R. Munkittrick, W.R. Parker & E. Blair. 2004. Effects of pulp mill effluent on fish communities. Poster. Environmental Effects Monitoring Science Symposium. February 16-18, Fredericton NB.
Freedman, J.A., R.A. Curry, K.R. Munkittrick, W.R. Parker & E. Blair. 2004. Effects of pulp mill effluent on fish communities. Canadian Conference for Fisheries Research, January 8-10. St. John’s NFLD.
Freedman, J.A. & D.L.G Noakes. 2002. Why are there no really, really big bony fishes? A comparison of maximum body size between teleosts and elasmobranchs. Poster. Ecological and Evolutionary Ethology of Fishes. August 2002, Quebec City QC.
Freedman, J.A. 2001. Why are there no really, really big bony fishes? Ontario Ecology and Ethology Colloquium. May 2-4, Guelph ON.
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