Assessing Stock and Fishery Status of Spawning Alewife, Alosa

ASSESSING STOCK AND FISHERY STATUS OF SPAWNING ALEWIFE, ALOSA

PSEUDOHARENGUS, IN THE GASPEREAU RIVER, NOVA SCOTIA, BY USING

VIDEO COUNTS TO ESTIMATE SPAWNING RUN SIZE AND ESCAPEMENT

Jordan J. Bonang

Thesis submitted in partial fulfillment of the

Requirements for the Degree of

Bachelor of Science with

Honours in Biology

Acadia University

March, 2016

This Thesis by Jordan J. Bonang

is accepted in its present form by the

Department of Biology

as satisfying the thesis requirements for the degree of

Bachelor of Science with Honours

Approved by the Thesis Supervisor

______

Trevor Avery Date

______

Jamie Gibson Date

Approved by the Head of the Department

______

Dr. Brian Wilson Date

Approved by the Honours Committee

______

Dr. Anna Redden Date

I, Jordan J. Bonang, grant permission to the University Librarian at Acadia University to

reproduce, loan or distribute copies of my thesis in microform, paper or electronic

formats on a non-profit basis. I, however, retain the copyright in my thesis.

______

Signature of Author

______

Date

iii

Acknowledgements

First, I would like to thank Dr. Trevor Avery for stimulating my interest to get involved in an honours thesis. His support and guidance have been crucial factors towards the success of this project, not to mention, the abundance of paid lunches and informative conversations about the need-to-know characteristics of aquatic biology. I would like to thank Dr. Jamie Gibson for introducing me to the wonders of the Alewife and incorporating his passion for topics surrounding fisheries into every needed explanation. I especially thank Dr. Gibson for personally taking me to the field site and introducing me to all of the parties involved in the project. Collectively, I must thank both Dr. Avery and

Dr. Gibson for their extreme patience in my inability to master “R”. Their experience with the program and willingness to help were greatly appreciated along the way. Next, this project was only possible through the funding provided by Acadia University and the

Department of Fisheries and Oceans (DFO). I would like to thank both Acadia University and the DFO for supporting this research. To the members of Team Kraken, I am grateful for the many distractions from video analysis you presented, especially Brook Beauliua.

You salvaged a large proportion of my sanity. I would also like to thank Team Kraken members Julia Whidden and Danielle Quinn for allowing me to tag along on some of their weir and skate trawling adventures, anything for a break from visual counts. Lastly, to my girlfriend, Sarah Osborne, and to my housemates, Ben MacNeil, Justin Kearney and Eileen Haskett, I thank you for creating an enthusiastic and welcoming environment to come home to after a long day of counting Alewife.

I dedicate this thesis to the supportive members of the Bonang family, and their pseudo-understanding of the constituents of my thesis.

Table of Contents

Acknowledgements ...... iv

Table of Contents ...... v

List of Tables ...... vii

List of Figures ...... viii

Abstract ...... xi

Introduction ...... 1

Fisheries Status ...... 2

Main Objectives...... 2

Ecological Role and Habitat Requirements ...... 3

Life Cycle ...... 4

Population Dynamics Drivers...... 5

Stock Assessment, Escapement and Reference Points ...... 6

Exploitation and Management ...... 8

Study Site...... 9

Licenses and Fisheries ...... 11

Maritime Assessments ...... 12

Materials and Methods ...... 14

Video Recordings ...... 14

Video Sampling ...... 15

Resolving Video Issues ...... 16

Sampling and Abundance Estimation ...... 17

Missing Values ...... 20

Evaluation of Fishery Status ...... 21

Results ...... 22

Escapement Estimates ...... 22

Total Escapement ...... 23

Landings Count, Annual Run Size and Exploitation ...... 23

Alewife Stock and Fishery Status ...... 24

Discussion ...... 24

Stock and Fishery Status ...... 25

Study Site Enhancements ...... 28

Video Formatting and Compression ...... 28

Biological Characteristics ...... 29

Recruitment ...... 30

References ...... 31

List of Tables

Table 1. An overview of the main goals set by the implementation of the Gaspereau

River Fisheries Management Plan prior to the 2002 fishing season (DFO, 2007; McIntyre et al., 2007) ...... 37

Table 2. A table depicting the selected hour groupings for the period stratum. Three time samples (units) were randomly selected from each period per day...... 37

Table 3. Gaspereau River Alewife (Alosa pseudoharengus) spawning run harvest data including reported landing counts from logbooks measure, the logbook reporting rate and

Fishery Officer pail count estimates from 1986 – 2006 (from McIntyre et al., 2007)...... 38

Table 4. Mean estimates and standard deviation (SD) of Alewife (Alosa pseudoharengus) escapement for all 5 strata over the 38 days of the 2015 Gaspereau River spawning run.

The maximum mean estimate, 261.5, was on 15 May in strata 4, and the maximum standard deviation, 121.2, was on 20 May in strata 5...... 39

Table 5. Compilation of annual logbook recordings and catch estimates from Gaspereau fishermen and estimates of escapement, run size and exploitation rate over 15 years from

1970 – 2006 from Gaspereau River Alewife (Alosa pseudoharengus) spawning runs at the White Rock dam fish ladder (from McIntyre et al., 2007). Data for the 2015 spawning run was added to provide additional information about the dynamics of escapement and exploitation. Asterisks indicates usage of interpolation or extrapolation...... 40

vii

List of Figures

Figure 1. Estimates of Alewife (Alosa pseudoharengus) landings counts taken from 21 years of Gaspereau River, NS, spawning runs from 1986 – 2006. Landing counts were obtained from McIntyre et al (2007)...... 41

Figure 2. The five major river systems that empty into the Minas Basin; Cornwallis River

(C), Gaspereau River (G), Avon River (A), Shubenacadie River (Sh) and the Salmon

River (S)...... 42

Figure 3. The Bay of Fundy splitting into two regions, northeast Chignecto Bay (C), and

Minas Basin (M). The marking indicated the location of the Gaspereau River, Kings

County, Nova Scotia, at 45.12°N, -64.27°E, and its proximity to the Minas Basin...... 43

Figure 4. A longitudinal view of the new concrete White Rock fish ladder, built in 2002.

...... 44

Figure 5. An internal view of the hydroelectric video monitoring facility located at the top of the concrete White Rock fish ladder. The recording device captures video samples, and stores them on a desktop computer...... 45

Figure 6. Alewife (Alosa pseudoharengus) crossing the absolute top of the White Rock fish ladder, within the field of view of the recording device. A magnified view of Alewife crossing is in the top left corner. The red arrow points upstream. The total number of fish moving upstream, corrected for the number that temporally drop back downstream, is considered a unit of escapement...... 46

viii apparent during high movement mid-day periods (strata 2 – 4). Lower estimates were observed during periods of low fish movement (strata 1 and 5). Maximum mean daily estimate was 261, which was observed on 15 May, for stratum 4 (Table 4)...... 47

Figure 8. A bubble plot showing the number of Alewife (Alosa pseudoharengus) estimated to have ascended the White Rock fish ladder on the Gaspereau River, NS, by day and by strata, from 9 May(Day 1) – 15 June 2015 (Day 38). The strata represent the time blocks used in the two-way stratified random sampling design (see Table 2). Bubble size is proportional to the number of fish moving in each strata by day, and are scaled to the maximum total estimate of 13,752 fish. Open circles indicate counts of zero...... 48

Figure 9. A bubble plot showing the ratio between the standard deviation and the mean,

CV, for the number of Alewife (Alosa pseudoharengus) estimated to have ascended the

White Rock fish ladder on the Gaspereau River, NS, by day and by strata, from 9 May –

15 June 2015. The strata represent the time blocks used in the two-way stratified random sampling design (see Table 2). Bubble size is proportional to the number of fish moving in each day and strata, and are scaled to the maximum CV, of 1.73. Open circles indicate zero variability...... 49

Figure 10. A scatterplot with connected lines showing mean Alewife (Alosa pseudoharengus) escapement estimates with upper and lower ends of calculated 95% confidence intervals during the Gaspereau River, NS, spawning run from 9 May – 15

June 2015. Day 1 is the first day of the run, 9 May, and day 38 is the last day of the run,

15 June. Higher mean counts were observed during mid-to-late May...... 50

Figure 11. Estimates of Alewife (Alosa pseudoharengus) escapement taken at the White

Rock fish ladder from 14 years of Gaspereau River, NS, spawning runs from 1983 –

2015. Escapement estimates from 1983 – 2006 were obtained from McIntyre et al (2007).

...... 51

Figure 12. Estimates of total Alewife (Alosa pseudoharengus) abundance, or total run size, during 14 years of Gaspereau River, NS, spawning runs from 1983 – 2015. Run size estimates from 1983 – 2006 were plotted as calculated by McIntyre et al (2007)...... 52

Figure 13. Estimated Alewife (Alosa pseudoharengus) exploitation rates from 14 years of Gaspereau River, NS, spawning runs from 1983 – 2015. Exploitation rates from 1983

2006 were obtained from McIntyre et al (2007)...... 53

Figure 14. Assessment summary showing the status of the Gaspereau River, NS, Alewife

(Alosa pseudoharengus) stock and commercial fishery relative to reference levels for fishing mortality rates and spawning escapements used to assess the status of the stock.

Results from 1982 – 1984 are shown as open circles, and from 1997 – 2006 as closed circles. The large black circle shows 2015 results derived herein. The relationship between the ratio of total escapement (E) to upper stock reference level (USR), and of exploitation (U) to removal reference level (URR), were used to evaluate the status of the stock and the fishery. [Adapted from Gibson and Bowlby (in press)]...... 54

Abstract

Alewife, Alosa pseudoharengus, are an anadromous species of fish that are harvested commercially as they ascend rivers to spawn in the Spring. In 2001, an assessment of the Alewife population in the Gaspereau River revealed that the stock was heavily exploited resulting in the establishment of a fisheries management plan with two primary goals: 1) to reduce fishing mortality and 2) reach a spawning escapement of

400,000 adults. Based on assessments of stock and fishery status from each year up to

2006, the management plan did reduce the exploitation rate, and the escapement more than doubled over values in the late 1990s. Since 2002, video monitoring at the White

Rock fish ladder has occurred annually during the spawning run, but video after 2007 was not analyzed for Alewife counts. Counts for 2015 were undertaken, and, using a two-way stratified statistical sampling design, escapement and daily run size were estimated. A total escapement of about 437,000 Alewife was estimated. These estimates will provide information about the 2015 spawning run in the Gaspereau River system with respect to management goals. Commercial landings on the river were provided by the Gaspereau

Fishermans Association and were combined with the escapement estimate to estimate a total run size of approximately 1,060,000 fish. A time series of 14 years of escapement estimates and exploitation rates for Alewife in Gaspereau River spawning runs, consisting of years 1982 – 1984, 1995 – 2006, and 2015, were summarized to make inferences about the recovery of the Alewife stock and fishery to its present status.

Introduction

The Alewife, Alosa pseudoharengus Wilson 1811, is one of two species of fish along with Blueback Herring, Alosa aestivalis Mitchill 1814, that are collectively referred to as river herring. They are both important anadromous fish species because they support commercial and recreational fisheries when ascending natal riverine and estuarine ecosystems, and also play important ecological roles. As adults, Alewife spatial distribution is located along the Atlantic coast of North America from the Gulf of St.

Lawrence and Nova Scotia to North Carolina. The distribution of blueback herring is mainly along the Western Atlantic, extending from Cape Breton, Nova Scotia south to the

St. John’s River, Florida. Freshwater landlocked populations of river herring are not uncommon between the extreme points of distribution (Berry, 1964; Winters et al., 1973;

Fay et al., 1983). Overall, both species are similar morphologically and genetically, and share similar life histories.

There is evidence that both Alewife and Blueback Herring employ natal homing to locate natal rivers and estuaries for ascension. Evidence of olfactory system usage as a sensory mechanism for natal homing has been observed (Thunberg, 1971), but natal river spawning does not have perfect site fidelity. Natural straying and resultant changes in gene flow have been documented (McBride et al., 2014). As such, populations in individual rivers can be thought of as more or less genetically discrete, which defines the basis for conducting individual assessments.

Over 100 rivers in the Maritime Provinces of Canada (hereafter Maritimes) support river herring populations and many support co-existence of Blueback Herring and

1 the more abundant Alewife. The study site of this project, the Gaspereau River, Nova

Scotia, supports only Alewife.

Fisheries Status

Important Alewife fisheries exist in most coastal regions of the Atlantic along the

Eastern United States and the Maritimes. The scope of this project includes an important and historical effector on Alewife population dynamics, fishing pressure, which has historical periods of overexploitation. In 2015, overexploitation and a high potential of extirpation led to Alewife being listed as a mid-priority candidate on the Species

Specialist Subcommittees’ (SCC) Candidate List for assessment by the Committee on the

Status of Endangered Wildlife in Canada (COSEWIC, 2016); this followed a request in

2011 to be listed as threatened in the Eastern United States by the National Resources

Defense Council (NRDC) under the Endangered Species Act (ESA) (NMFS, 2012).

Main Objectives

The goals of this project were to achieve an annual estimation of run size and total escapement of Alewife from the Gaspereau River, and to assess the overall health of the

Alewife population in the Gaspereau River system. The number of Alewife that escape the fishery reproduce and contribute to future spawning runs. Knowledge of this population will contribute to a better understanding of the status of Maritime Alewife stocks. Information gained here may be transferable to other populations or stocks. Video was captured by a recording device installed at the White Rock Dam. The device was installed by NSPI in a video monitoring facility located at the top of the Gaspereau River system. The video archive will be acquired from NSPI, and will be used to quantify the escapement of Alewife. The last stock assessment for the Gaspereau River was conducted

2 in 2007 (McIntyre et al). The 2015 annual run size estimate for the Gaspereau River

Alewife fish stock will be the first conducted in almost 8 years, and is information necessary for management.

Ecological Role and Habitat Requirements

Alewife are of great importance to their respective ecosystems. They are considered voracious predators of zooplankton during non-spawning periods and may even alter zooplankton community composition (Mullen et al., 1986). During spawning periods, an assessment of the stomach contents of Alewife conducted by Cooper (1961) revealed that adult anadromous Alewife actually feed on very small quantities of zooplankton, and this feeding is suppressed until the spawning event is concluded.

Alewife act as important nutrient vectors between marine and freshwater systems via egg deposition, excretions, and mortality that ultimately contribute to system productivity

(Mullen et al., 1986; West et al., 2010). Alewife are also considered important prey for forage by an abundance of marine and freshwater species such as Atlantic Cod, Gadus morhua Linnaeus 1758, Striped Bass, Morone saxatilis Walbaum 1972, and many species of birds (Loesch, 1987; Nelson, 2006).

Alewife spawning grounds consists of lakes, ponds or slow flowing parts of rivers during the period May – June in northern habitats (Mullen et al., 1986). Preferred spawning areas are of low depth (e.g. 15 cm – 3m) and low water flow and contain gravel, detritus, submerged vegetation or sand as substrates (Edsall 1964; Mansueti and

Hardy, 1967). Habitat preference of Alewife is largely dependent on its life cycle stage.

Life Cycle

The Alewife is an anadromous species meaning it moves from salt water (i.e. ocean) to spawn in freshwater (i.e. lake, pond, river). Alewife mature at ages 3 – 6 with evidence of some fish surviving for up to 10 years (Loesch, 1987). Adults return to their natal rivers and migrate upstream to spawn. Alewife are iteroparous, and will typically spawn 4 – 6 times over their lifetime (Loesch, 1987; Gibson and Myers, 2003). Alewife spawning runs begin in response to water temperatures between 5°C and 10°C, and the minimum temperature at which spawning occurs is 10.5°C (Cianci, 1969; Loesch, 1987).

Because spawning is dependent on temperature, it begins in the southern United States and progressively moves northward as coastal waters, rivers, and estuaries warm.

Consequently, in southern populations, spawning begins in December and February, and in northern populations, spawning begins in May and June (Sismour, 1994; O’Connell and Angermeier, 1999). In Atlantic Canada, adults begin ascending natal rivers that empty into the Bay of Fundy to spawn beginning late April (Stone et al., 1992), and spawn from late March through July (Mullen et al., 1986). Adult Alewife may continue to spawn for up to 6 weeks; thereafter, they use tidal regions of coastal rivers and calm portions of the non-tidal system, which include ponds, lakes and slower flowing reaches, as nursery habitats (Stone et al., 1992; Sismour, 1994). Alewife eggs are deposited in still water and hatch after 5 – 8 days. The larval stage includes a period of yolk-sac absorption when larvae have a mean total length (TL) of 5.1 mm (Mansueti, 1962; Norden, 1967;

DFO, 2001). Juvenile Alewife have a mean TL of about 20 mm (Mullen et al., 1986).

Juveniles in Atlantic coastal populations emigrate from freshwater to estuarine habitats

4 between June and November, and remain at sea until sexual maturity is reached (Loesch,

1987; Gibson and Myers, 2003).

Population Dynamics Drivers

Alewife population dynamics can be affected by the lack of physiological adaptation to changes in water temperature or solute content due to pollution, decreased access to spawning locations, anthropogenic introductions, increased predation, food availability and fishing (Neves, 1981; Lepak and Kraft, 2008; Butler, 2012). These factors may induce spawning failure, habitat contamination or mortality which may consequently affect the productivity of natal watersheds (Houde, 1989). Recent fluctuation in the temperatures of coastal waters indicated by global warming indices may present complications to Alewife physiology. For example, a drastic change in temperature can alter cell membrane permeability and can induce a loss of ion transport regulation and membrane enzymatic functionality (Hazel and Williams, 1990; Hazel,

1993). Additionally, in Lake Michigan, a large Alewife mortality event was thought to be caused by high water temperatures that induced a bloom of blue-green algae (Williams,

1968). Alewife already under stress from warmer waters would probably have a decreased ability to cope with the severity of environmental change caused by the bloom.

As for solute content, two studies showed that low levels of freshwater iodine can cause thyroid hyperplasia and an exhaustion of thyroid function (Hoar, 1952; Robertson and

Chaney, 1953; Brown, 1968).

In addition to predation, high rates of fishery exploitation may lead to negative effects on population dynamics, such as decreases in abundances of both first time and

5 repeat spawning Alewife, decreases in Alewife size and age at maturity and, if overexploitation persists, a decline in stock status (Jessop, 2003).

Stock Assessment, Escapement and Reference Points

Stock assessments and fisheries dynamics typically incorporate species biology on a stock-by-stock basis to set harvest levels (Hillborn and Walters, 1992). A fish stock is an isolated group of one fish species consisting of a subpopulation, population, or some other amalgamation of these two. Stock assessments are employed to ensure the productive sustainability of a fish stock, and start with understanding the parameters of population dynamics (Hillborn and Walters, 1992). To effectively sustain production in a stock, regulations are verified and upheld by management committees (Hillborn and

Walters, 1992). Fisheries management decisions should consider economics, biology and society. Societally, fishermen that rely on the resource, and their responses to management decisions, must be taken into account in order to achieve cooperative progress in management.

The most effective method for stock assessment is to consider population dynamics along with the collection of commercial catch and effort data (Hillborn and

Walters, 1992). Two commonly employed mechanisms to acquire catch and effort data are: 1) port sampling where records of landings or sales are passed to a management agency for compilation, and 2) log books where fishermen keep track of catches and report to a management agency. Catch logging is considered an indirect method because fishermen are reporting their species-specific landings data as a second party to management (Hillborn and Walters, 1992). For example, log book catch data was used to create an incomplete time series of Alewife commercial landings in the Gaspereau River,

NS, over 21 years spanning 1986 – 2006 (Fig. 1). This information is integral to the development of management plans.

The magnitude of annual yields, or catches, in fisheries are commonly regulated as a result of biological reference point implementation. A reference point is a reference level and is set in consideration of both the biological characteristics of a target fish stock and its respective fishery (Gibson and Bowlby, in press). This project implements two reference points; a removal reference level (RR) and an escapement reference level (Esc).

RR strives to define an acceptable rate of fishing removals from a system, often derived from the rate of fishing mortality rate that results in the production of a maximum sustainable yield (Fmsy) (Gibson and Bowlby, in press). Esc strives to create a target escapement for a population that will produce the maximum sustainable yield (MSY) for subsequent generations (DFO, 2012). Escapement is defined as the “escape” of fish from fisheries activities, and relates directly to potential for upstream spawning. Reference points account for all available data for a stock and are system-specific (e.g. river specific). Reference points for a stock are better estimated as the time series of available catch data lengthens (DFO, 2012).

Stock abundance trends reveal temporal variability in productivity that help to calculate reference points in consideration of variability. When sufficient data is not available for a stock, default reference points may be implemented. The precautionary approach (PA) framework is one method to assign reference points or to infer a MSY in terms of the maximum acceptable RR (DFO, 2012). “Data Deficient Stocks”, or stocks with deficiencies in assessments, can be assigned default reference points through a combination of available information and application of the PA. “Modelled Stocks” also

7 employ the PA, but are given reference points as a result of the availability of a time series of catch data sufficient to calculate reference points. Reference points are subject to ongoing revision and modification as information becomes available. Changes may occur because of new information regarding species interaction, changes of crucial environmental conditions or in response to seasonal exploitation rates (DFO, 2012).

Information about escapement and exploitation for a stock are classified into three status zones; healthy, cautious and critical (DFO, 2012). A limit reference point (LRP) is the boundary between the critical to cautious zones. If the exploitation rate (U) is below this point, harmful and long-term effects on a population are likely. An upper stock reference (USR) is the boundary between the cautious to healthy zones. If the total escapement (E) is below this point, a decrease in RR is encouraged to ensure a reduction in chance of reaching the LRP (DFO, 2012). Optimal results would yield an exploitation rate, U, below the URR, and a total escapement, E, above the USR.

Exploitation and Management

The rate of exploitation, U, can be defined as the ratio of the quantity of fish that die due to fishing mortality in one season to the total number of fish that occurred in that particular fishing season (i.e. the spawning run size) (Ricker, 1975). Fisheries management aims to use all available data regarding a population and to employ measures that will encourage U to return to reference point levels, thus reducing or increasing mortality rates. Mortality is an important metric and can be categorized into two subclasses: fishing mortality (human removal) and natural mortality (e.g. predation, disease, natural death) (Ricker, 1975).

For this study, exploitation rate, U, and spawning escapement, E, will be the foci.

A stock will grow in abundance (size) because of a reduction in fishing effort (F) measured most often as gear applied during a specific period of time or because of recruitment (R) which is the addition of new fish to the stock from smaller size categories

(e.g. first-time spawning adults from juveniles) (Ricker, 1975). In contrast, a stock can decrease by an increase in fishing effort that reduces spawners and recruits. An additional factor that contributes to U is the vulnerability, or catchability, of fish. Vulnerability is defined as targeting of subcategories of species, or the location in which the species resides. In the case of anadromous fishes, vulnerability can be targeting a specific size class, or targeting of a specific range along a natal river.

Study Site

The focus of this project is the Gaspereau River and its annual upstream migration of an Alewife fish stock for eventual spawning. The Gaspereau River is one of five major river systems that feed into the Minas Basin and is fed by streams and the Black River tributary (Nash and Stewart, 1990). The other major rivers are the Cornwallis River,

Avon River, Salmon River and the Shubenacadie River (Fig. 2). The Minas Basin is one of two subdivisions of the northeastern boundary of the Bay of Fundy (Fig. 3). At Cape

Chignecto, the tides of the Bay of Fundy split into a northeastern section, Chignecto Bay, and an eastern section, Minas Basin. In this region, tidal currents and amplitudes are extremely dynamic and create high turbidity, especially in the Minas Basin. The

Gaspereau River is exposed to tidal influence up river to the Melanson Bridge, an unchanging geographic feature set as the practical upper saline water mark. Further

9 upstream, the river is influenced solely by freshwater, unless rare tidal extremes extend past Melanson Bridge.

The Gaspereau River watershed has undergone a series of structural modifications over the past 100 years in order to facilitate the implementation of hydroelectric generation. The White Rock hydroelectric dam and its corresponding fishway were originally constructed in 1919 and 1920, respectively (McIntyre et al., 2007). After hydroelectric integration, major developments towards fish diversion took place in upper regions of the watershed, and by 1930, the anthropogenic alterations continued as multiple dams were constructed to accompany additional storage and power-generation

(McIntyre et al., 2007). The water supplied to the five hydroelectric stations comes from a variety of lakes that were interconnected as a result of both natural and artificial waterways (Gibson and Myers, 2001). These lakes are spawning habitats for Alewife.

Human-influenced alterations to the Gaspereau River watershed may negatively impact Alewife that use this watershed. These negative effects are largely mitigated by the application of fish ladders (fishways), spillways, control gates and diversion screens

(McIntyre et al., 2007) implemented and maintained by Nova Scotia Power Inc. (NSPI).

These structures allow Alewife to use this watershed through maintaining upstream migration corridors to natal spawning habitats, and by providing passage for descending spawned Alewife and their progeny. These structures aim to divert Alewife from the harmful effects of the turbines of the five hydroelectric generation stations and reduce direct and in-direct biological and physiological effects, including stress. Previous

Alewife biological and stock assessments on the Gaspereau River watershed contributed to modifications of these structures to positively affect species health.

McIntyre et al (2007) outlined specific mechanical upgrades that were implemented to increase the efficiency and safety of the White Rock dam. Downstream bypasses were constructed so fish could avoid a dam positioned at the lower end of the system. Prior to the 2002 fishing season, a previously used wooden fishway was decommissioned, and a new concrete fishway on the main diversion dam was constructed

(Fig. 4). The new White Rock Fishway included a video monitoring facility located at the upper reaches of the Gaspereau River system, 2 km upstream of the White Rock hydroelectric facility (Fig. 5). In this facility, video capture is used to monitor the passing of Alewife (upstream spawners) that escape the commercial fisheries (Fig. 6).

Licenses and Fisheries

Generally, Alewife support directed and by-catch fisheries both during their coastal migrations, and during ascension of rivers during the annual spring spawning run

(O’Gorman, 2010). Fishermen use the dynamic tides of the Bay of Fundy and knowledge of the behaviour of Alewife to increase harvesting efficiency. For example, fishers of the

Avon River estuary employ a traditional method of commercial drift net fishing to harvest Alewife on flood tides, while those of the Shubenacadie River employ the same method further upstream. Additionally, brush weirs are located around the Minas Basin

(e.g. Economy Point, Five Islands, Bramber), and support commercial fisheries that include Alewife (Stone and Daborn, 1987; Whidden, 2013). Gaspereau River commercial fisheries mainly use gillnets within the tidal waters of the lower reaches, while weirs and square dip-nets are used in non-tidal waters (i.e. above the tidal influence or Melanson

Bridge) during spawning runs (Jessop and Parker, 1988). The majority of landings for the

Gaspereau River watershed are taken in the dip-net fishery.

The Gaspereau Fishermen Association consists of 18 fishermen that are directly involved in the fisheries on the Gaspereau River. Sixteen of these members operate under square net (dip-net) licenses, one operates a drift net license, and one operates a gillnet license (McIntyre et al., 2007). The commercial fishing season runs from 15 March to 30

May. It is important to note that the recreational fisheries on this river system are not reported, but are considered to be insignificant in relation to the annual harvests from commercial landings, because of both the low retention limits and low number of participants.

Maritime Assessments

In 1994, a survey was conducted on the distribution of Alewife in the Maritimes rivers. It was found that of the 145 rivers included in the survey, Alewife was found in

141 (Rulifson, 1994). A formal region-wide assessment pertaining to Alewife stock status and corresponding fisheries of watersheds in the Maritimes was conducted by DFO in

2001. The report assessed 12 rivers that contained Alewife populations including the

Miramichi River, Margaree River and Gaspereau River. All rivers contained both Alewife and Blueback Herring stocks except for the Gaspereau River. The stock status of the

Miramichi River showed that both species of fish were being exploited at or above reference levels, with the expectation that annual abundance and exploitation rates in

2001 would be below and above reference levels, respectively (DFO, 2001). The

Margaree River was shown to contain low abundances for both species of fish; however, a reduction in fishing effort in 1996 reduced exploitation rates to near reference levels from 1997 – 2000 (DFO, 2001). The Gaspereau River assessment showed that the status of the stock was heavily impacted by exploitation rates that exceeded the reference level

12 of 65%. Since 1960, reported landings for river herring in the Maritimes peaked in 1980 with a total of 11,600 50 lb pails, and averaged a total of 6,231 pails over 1997 – 1999

(Table 3; DFO, 2001).

Gaspereau River Alewife stock status assessments were conducted in 1988

(Jessop and Parker 1988) and in 2001 (Gibson and Myers 2001). Gibson and Myers

(2001) provided results from studies during 1997 – 2000 pertaining to the landings data, biological data, and available counts for the Gaspereau River stock. They used the data to model the population dynamics and to generate biological reference points for this fishery. From 1997 – 2001, it was found that the exploitation rates were relatively high compared with values in the 1980s (mean = 73%, range: 33 – 89%). Catch data also revealed that exploited Alewife belonged primarily to two age classes, suggesting that this stock lacked age-class diversity. Mean spawning run size was 537,000 (range:

265,000 – 1,082,000) fish, but only 81,326 – 171,639 fish were escaping the fishery and exploitation rates were estimated at 88% and 89% in 1999 and 2000, respectively (DFO,

2001). The assessment concluded that E of 400,000 – 450,000 spawning adult Alewife would result in the maximum sustainable yield, MSY, and ensure a stable, and sustainably fishable population.

Following the 2001 assessment, a new fishery management plan was implemented that strived to achieve a reduction in fishing mortality and adhere to a U of 64%, which was a reference point that would produce a MSY for subsequent generations. To reduce fishing mortality, commercial and recreational fishermen were reduced from five to four fishing days per week. The plan aimed to meet target E of 400,000 adults (refer to Table

1 for formal objectives). Prior to the 2002 fishing season, members of the Gaspereau

Fishermen Association were gathered to consult regarding the implementation of the plan. It was agreed that the periods of 9:30 PM Friday to 5:30 AM Monday and 9:30 PM

Tuesday to 5:30 AM Thursday would remain closed to commercial catches of Alewife.

Mean E from 2002 – 2006 was 279,278 fish, which was considerably higher than the

1997 – 2000 mean of 111,823 fish (DFO, 2007). From 2002 – 2006, the actions of the management plan have managed to reduce U and more than double E over values in the late 1990s. However, as of 2007, E had yet to reach the escapement target of 400,000 adults, with the exception of E for 2003 (McIntyre et al., 2007). Therefore, a data gap in formal assessments of Alewife escapement from the Gaspereau River commercial fisheries exists from 2007 to present.

Materials and Methods

The total number of fish passage during a particular spawning run of Alewife is arguably the most important factor in population dynamics (Nelson, 2006). With enough annual observations of total escapement, E, coupled with commercial landings, a time series of annual run sizes can be compiled and compared with landings with the goal of determining stock health through examining trends over time. Visual counts of migrating

Alewife were used to quantify the 2015 annual E and to aid in a better understanding of the stock status in the Gaspereau River.

Video Recordings

Videos capturing Alewife escapement were recorded in the video monitoring facility located at the top of the White Rock Fishway at the White Rock Dam in the upper reaches of the Gaspereau River in Kings County (45.12°N, -64.27°E), Nova Scotia (Fig.

3). The video archive was obtained from Nova Scotia Power Inc. (NSPI) through a

14 relationship with Fisheries and Oceans Canada (DFO). The video archive ranged temporally from 16 April – 16 June 2015. The spawning run duration (D; in days) was calculated between the day at which fish began to climb the ladder to the last day fish were observed. In order to achieve an annual run size estimate (Y) for the year of 2015, the total number of adult Alewife that escaped Gaspereau River commercial fisheries, E, was quantified, and subsequently, combined with the 2015 landings counts derived from

Gaspereau Fishermen Association logbooks.

Video Sampling

A total of 5,856 videos (1,464 hours of footage), each 15 minutes in duration, were made available. Videos were saved to a computer and compressed to Audio Video

Interleaved (AVI) format. It was not possible to observe all videos because funds and employees or volunteer participants were limited. Therefore, a random sampling design was implemented that allowed for a representative sample to be analyzed effectively and efficiently. A total of 570 video segments, each 5 minutes in duration, were randomly selected for analysis from those available using a 2-way stratified random sampling design (2WS). Fish moving up and down the fish ladder were counted visually by watching video segments on VLC media player (VLC 2.2.2, VideoLAN). Fish were manually counted using two hand-held tally counters; one for upstream counts, one for downstream counts. Each completed count was considered representative of the number of fish ascending the ladder during that time period. Details of sampling of video segments are provided below.

Resolving Video Issues

Many video segments contained footage that was uncountable due to the number of fish passing at one instant, especially within mid-to-late-day periods (14:00 – 18:00 hr) during peak movement times of the spawning run (Table 2). Crowding during spawning runs often resulted in milling behaviour, in which the Alewife swam haphazardly in the camera field making it difficult to count upstream and downstream net movements. A majority of these segments could be slowed to 50% or 25% speed using AVIdemux software (v2.6.10). Directionality was much more apparent at lower speeds and escapement was more easily tallied.

Lighting installed above the recording device was used to monitor nighttime passages and to ensure clear vision to the bottom of the passageway. The lighting system appeared to be malfunctioning during some segments as it flickered or appeared abnormally dim. Severity dependent, this problem was most times able to be solved by adjusting the contrast, brightness and colour filtering options contained within

AVIdemux. If the water was still below the camera, a movement vector option was activated to catch the faintly visible Alewife. Rough water conditions decreased the success of vector application as it keyed focus to turbulent splashing. At the bottom of the fishway below the camera, a white plastic sheet was used as a backdrop to increase contrast between dark-colored Alewife from the white sheet below. The accumulation of debris upon the sheet decreased visibility. This was sometimes overridden by increasing video brightness. When both the plastic sheet and lighting system were compromised, and digital filters were unsuccessful in correcting the issues, especially during peak spawning days and periods, some segments were unable to be assessed.

Finally, video segments during times of camera device malfunction contained a black screen for a majority of the video which prohibited observations. Malfunctions were believed to be caused by a loosened video signal. This issue occurred in two of the randomly selected video segments.

Sampling and Abundance Estimation

The 2WS sampling design was used following Nelson (2006) to produce reliable estimates of mean, and total escapement, E. Stratification occurred over two levels. The first stratum was by day (d). The second stratum was by period (p). Periods were broken down into sets of hours that formed five strata created to reduce variability based on the understanding of Alewife behaviour and movement (Table 2). The rationale behind the hours of the day contained within each strata pertains to migratory patterns in fish. There are more fish migrating upstream in the warmer water temperatures in the mid-to-late hours of the day (i.e. 14:00 – 18:00 hr), whereas hours of the day with colder temperatures (i.e. 20:00 – 24:00 and 24:00 – 8:00 hr) experience less fish migration. For this reason, hours with observed similarities in fish migration were wisely grouped into the same strata to reduce variability among samples. In 2WS, each five-minute video segment is called a time unit (t). Each t within strata has an equal chance of being randomly selected and where the selection of one t is independent of another (Cochran,

1963; Nelson, 2006). A group of three time units, t, were randomly selected from each of the five periods, p, on each day, d, of the spawning run. In order to assess the efficiency of the 2WS methodology, the stratification scheme strives to achieve a confidence interval that is ± 10% of the total escapement estimate. Efficiency of the stratification scheme can also be assessed by calculating coefficients of variation (CV). A CV

17 compares the ratio of the standard deviation to the mean. Answering the question of effectiveness and efficiency of the scheme will provide a methodological basis for future projects, either encouraging or discouraging modifications to 2WS (i.e. increasing samples per strata, altering strata periods, or altering number of strata).

The total number of observations (O), or time units (video segments) counted, was found by multiplying the duration of the run, D, by the total number of periods and the total number of time units counted within each period:

푂 = 퐷 ∙ 푝 ∙t (Eq. 1)

Alewife moved through both directions of the camera field of view (Fig. 6). Since only upstream migrating fish are considered escaped individuals, both upstream and downstream movements were counted and the difference calculated to determine net migration. Two hand-held tally counters were used to assess upstream (EU) and downstream (ED) movements, respectively. Escapement estimates for each time period were calculated by:

퐸푑푝푖 = 퐸푈푑푝푖 − 퐸퐷푑푝푖 (Eq. 2) where Edpi was the number of fish moving upstream (escapement) for the ith count in period p on day d. Mean period estimates of Alewife escapement were estimated as:

푛 ∑ 푑푝 푖=1 퐸푑푝푖 푋푑푝 = (Eq. 3) 푛푑푝 where Xdp was the mean estimate in period p on day d; Edpi was the ith estimate per time unit t per day d, and ndp was the number of time units sampled during period p on day d

(typically, 푁푑푝 = 3). The total annual escapement, E, was found by summing mean estimates over the length of the spawning run and number of periods per day, and multiplying it by the number of time units per period:

퐷 푃 퐸 = ∑푑=1 ∑푝=1 푁푑푝 ∙ 푋푑푝 (Eq. 4) where Ndp was the number of time units t during period p; P was the number of periods during day d; and D was the number of days in the run. Variance for each day was calculated as:

푛 2 ∑ 푑푝 푖−1 (푋푑푝−퐸푑푝푖) 푉푑 = (Eq. 5) 푛푑−1 where Xdp, the mean estimate in period p of day d, and Edpi, the ith estimate on period p of day d, were summed over period p and day d of the run, and nd was the number of time units sampled on day d. The total run variance (VT) was calculated by:

퐷 푃 푉푑 푉푇 = ∑푑=1 ∑푝=1 푁푑푝 ∙ (푁푑푝 − 푛푑푝) ∙ (Eq. 6) 푛푑푝

Confidence intervals for E were calculated by:

퐶. 퐼.95% = 퐸 ± 푆푡푎√(푉푇) (Eq. 7) 2

Since Ndp ≠ ndp, degrees of freedom (df) needed for the Student’s t-distribution (푆푡푎) 2 were estimated using the Satterthwaite approximation (Cochran, 1963):

퐷푃 (∑푑=1 푎푑푝∙ 푉푇) 푑푓 = 2 (Eq. 8) (푎 ∙푉 ) 퐷푃 푑푝 푇 (∑푑=1 ) 푛푑푝−1 where:

푁푑푝∙(푁푑푝−푛푑푝) 푎푑푝 = (Eq. 9) 푛푑푝

Daily estimates of escapement were obtained analogously using a 1-way stratified random sampling design. Estimates of escapement obtained within time units from the

2WS sampling design were compiled by day, using stratification by period, as a 1-way stratified random sampling design:

푛 ∑ 푝 푖=1 퐸푝푖 푋푝 = (Eq. 10) 푛푝 where Xp is the mean estimate of escapement in strata p. Estimates of daily escapement were found by summing mean estimates over all strata p and multiplying it by the number of time units per period:

푃 퐸푑 = ∑푝=1 푁푝 ∙ 푋푝 (Eq. 11) where Ed is the daily estimate of escapement in day d.

Missing Values

For all uncountable and uncorrectable time units, the first resolution was to substitute and assess an alternative time unit (video segment). The requirement for substitution was to replace the unusable time unit with a time unit from the same strata to limit among strata variability.

A second resolution was implemented when substitution within strata was not possible. In order to resolve this issue, two things were required: 1) an estimate of the mean number of fish moving in each missing strata, and 2) an estimate of its variance.

The mean number of fish moving in each missing strata was obtained by a generalized linear model (GLM) using a Poisson distribution, a distribution appropriate for count data. Successful mean estimates of escapement were used to produce coefficients relative to mean estimates by day, and mean estimates by strata. Coefficients were used to predict mean estimates of escapement to fill data gaps. A characteristic of count data is that the variance is expected to increase with the mean. The second requirement of predicting variances for data gaps utilized a linear regression. Intercepts were set to zero, and the slope of the regression line was used to predict variances. Variances were expected to increase with respect to the increasing number of counts.

Evaluation of Fishery Status

An important goal for the project was to assess the Gaspereau River system five- year fishery management plan that was implemented prior to the 2002 fishing season of a spawning escapement target, Esc, of ≥ 400,000 adults coupled with a reduction in exploitation rate, U, over values in the late 90s and early 2000s. In order to achieve an accurate estimation of run size, Y, the Gaspereau Fishermen Association provided 2015 landings counts. Temporal comparisons were made with annual catch pail data compiled from previous years (McIntyre et al, 2007; Table 3). It is important to note that run size estimates assume that E is not followed by illegal commercial fishing and that recreational fisheries do not make significant contributions to the annual harvest. Harvest totals (H), or total landings, can be added to the total annual escapement estimate E in order to estimate Y. Thus, run size estimates are given by:

푌 = 퐸 + 퐻 (Eq. 12)

A stock health and fishery status assessment summary adapted from Gibson and

Bowlby (in press) was used to combine estimates of E and U and to compare them to reference points previously defined for the Alewife spawning run in the Gaspereau River,

NS. The ratio between E for 2015 and an escapement USR of 400,000 was used as one variable, and the ratio between U and the exploitation URR of 53% (0.53) was used as the other variable. The LRP was set at 234,549 adults, and the rate of full exploitation was set at 35%. Optimally, U would be between the LRP and the URR, and E would be slightly above the USR. These estimates were compared to results from 13 years of Alewife spawning runs in the Gaspereau River, NS, from 1982 – 2006.

Results

The duration of the 2015 spawning run was found to be 38 days, lasting from 9

May – 15 June. A total of 570 time units (video segments) were observed to account for the 38-day spawning run; 78 (13.7%) of these time units were uncountable and 8 (1.4%) of these time units were missing from the archive. All 8 of the missing time units were able to be substituted within strata and 63 of the uncountable time units were able to be fixed by AVIdemux software or by substitution within strata. The remaining 15 uncountable time units were not able to be fixed or substituted. Data gaps in mean estimates, variances and standard deviations from uncountable time units were predicted by extrapolation.

Escapement Estimates

Escapement estimates for each time unit (video segment) were used to calculate mean estimates and standard deviation for each stratum by day (Table 4). High mean estimates of Alewife escapement during the spawning run were prevalent during mid-to- late May (13 May – 25 May 2015). Strata 2 – 4, in most cases, were consistent in containing higher estimates than strata 1 and 5, with a maximum mean estimate of 262 ±

78 Alewife on 15 May (Table 4; Fig. 7).

High estimates of total escapement during the run were prevalent during mid-to- late May (13 May – 25 May 2015) (Fig. 8). An estimate of escapement, from one stratum, of 13,752 Alewife occurred on 19 May in stratum 2. Mean estimates and corresponding standard deviations were compared to achieve a CV among strata by day. The maximum

CV was 1.73. Increased variability occurred in strata 1 and 5, indicating that the estimates derived from these strata produced larger deviations from the mean (Fig. 9).

Mean estimates were used to calculate estimates of daily escapement for each day of the run. These results shared the same trends as the mean estimates because all means estimates were compared within a constant number of time units (i.e. 3 time units) and periods (i.e. 5 strata). Confidence intervals (95%) were calculated for daily escapement estimates (Fig. 10). The highest daily estimate of escapement was 39,632 which occurred on day 10 of the run (18 May) (Fig. 10).

Total Escapement

E of Alewife in 2015 was estimated to be 436,879 fish (95% C.I. 412,628 –

461,129 fish) (Table 5). The upper and lower confidence level estimate of 24,230 is

5.54% of E, suggesting that the stratification scheme is precise and effective. The 2015 estimate of E was compared with 13 years of previous escapement estimates within the range of 1983 – 2006 (taken from McIntyre et al 2007) (Fig. 11). The 2015 E shows the most similarity to E from 2003 (Fig. 11).

Landings Count, Annual Run Size and Exploitation

Total landings, H, for 2015 in the Gaspereau River Alewife commercial fishery were provided by J. Gibson (personal communication) (Table 5). Harvest values were unable to be acquired for all 18 fishermen on the Gaspereau River during a DFO database query on 29 February 2016. Extrapolation was done relating the received H values to the total number of trapnets fished along the river and yielded an H estimate of 145,335 kg

(95% C.I. = 73,894 – 216,775 kg) (Table 5). Assuming that the mean Alewife weight is

233g (McIntyre et al., 2007), the estimated H during the 2015 Gaspereau River fishing season was 623,755 (95% C.I. = 317,143 – 930,367 fish) (Table 5). Therefore, Y, the annual run size, was estimated at 1,060,634 fish. The 2015 Y was compared with 13 years

23 of previous abundance estimates within the range of 1983 – 2006 (McIntyre et al 2007); and the 2015 abundance estimate is the largest of all years with estimates (Fig. 12).

The Alewife exploitation rate for 2015, based upon the ratio of H to Y, was 59%

(Table 5). The 2015 estimate of U was compared with 13 years of previous U estimates within the range of 1983 – 2006 (McIntyre et al 2007; Fig. 13). The 2015 U is much lower than values in the late 1990s, but higher than values in the early 2000s (Fig. 13).

Uncertainty exists in this estimate due to the use of extrapolation to estimate H.

Alewife Stock and Fishery Status

The 2015 U was above the URR, and E for 2015 was above the escapement USR, classifying the status of the fish stock in the healthy category, and the status of the commercial fishery as slightly overexploited (Fig. 14). A time series of 13 years within

1982 – 2006 was plotted on the assessment summary to provide temporal comparisons pertaining to Alewife stock and fishery status. Aside from the 2015 assessment summary, the only year containing a healthy U was 2003. From 2001 – 2003, and in 2005, the fishery was considered fully exploited. All other years in the temporal analysis were considered overexploited.

Discussion

This study conducted the first evaluation of the status of the Gaspereau River

Alewife spawning stock since 2007, and has provided the first long-term temporal analysis of the effectiveness of the fisheries management plan. Additionally, this project implemented a new strategy for visual escapement counts using videos coupled with a two-way stratified random sampling design.

Stock and Fishery Status

The 2015 estimates of E, total escapement, (436,879) and exploitation rate, U,

(59%) met the criteria of the 2002 fisheries management plan. Estimated E was greater than the USR of 400,000, and the estimated U was reduced over levels from the late

1990s. The assessment summary figure provides a visual representation of the relationship between these two measurements and classified the 2015 Gaspereau River

Alewife stock and fishery as healthy and slightly overexploited, respectively. It is not the goal to advocate enforcement of fishing restrictions to compensate for slight overexploitation due to the variability that exists on each of the estimates (i.e. E and H).

An increase in the accuracy of H may be achieved by acquiring accurate harvest data from logbooks and maintaining logbook reporting rates of 100%. An increase in the accuracy of E can be achieved by obtaining higher quality videos, which would eliminate the need for prediction by extrapolation. Additionally, accuracy may be improved, and variability reduced, if more time units are counted and the confidence interval on E is within 5%. This is discussed further below. Alewife stock and commercial fishery assessment precision would increase by reducing variability in both E and H; however, precision does not necessarily increase accuracy, depending on where the true mean lies.

Nonetheless, increased precision would increase the usefulness of assessments in a time series.

The analysis of a single year of data does not provide a definitive assessment of status, rather, it provides an indication of short and long term variability in E and H. From

1997 – 2006, exploitation rates, U, occupied all three exploitation zones; partially, fully and over, and all three escapement zones; critical, cautious and healthy. These changes

25 modeled a seemingly circular fluctuation, and were not successive. Likewise, although the 2015 estimate of E is larger in its respective time series, it is classified as slightly overexploited with an U that is 5.8% higher than the URR. Recent and frequent assessments pertaining to the stock and commercial fishery status of the Gaspereau River

Alewife must be conducted to learn more about modern characteristics of the population to avoid changes to the fishery based on the 2015 assessment.

Sampling Efficiency

The video sampling methodology for this project was developed from the 1-way stratified random sampling design from Davies et al. (2007). Davies et al. (2007) used 15- minute video sample units at the beginning of each hour from 08:00h – 16:00h for visual counts. Reducing the sampling unit (video segment) size and adding more sampling units achieves a greater level of statistical power (Davies et al., 2007). Additionally, within-day variability in a one-way stratified sampling design can be reduced by implementing an additional stratification to reduce sample clumping, which is an advantage of using a two- way stratified random sampling design. As well, a two-way stratified sampling design ensures the spreading of randomly selected time units. By implementing two levels of stratification (i.e. by period and by day), time units were able to be thoroughly distributed temporally (across each day). Additionally, a two-way stratified design was able to account for patterns in migration. Typically, Alewife will exhibit increased movement in mid-day periods, and by limiting the number of samples that can be selected from this period, this design can reduce the variance of E. A limitation presented by this design is that the maximum number of time units that can be selected per period is 3, and per day is

15. Variability reduces with increasing sampling size, thus, increasing the number of time

26 units selected per period would increase the precision of E. However, increasing time units will decrease efficiency. By adding two time units to each period (i.e. total of five per period), the number of time units (i.e. video segments) that would have had to be counted would increase to 950 (79 hr) from 570 (48 hr); an increase of 67%.

One goal for this study was to achieve a confidence interval on the estimate of total escapement within 10%. The confidence interval of ± 24,230 was 5.54% of E indicating that the goal was met, and the stratification design was effective. CV was used to assess variability and values were more variable in strata 1 and 5 over strata 2 – 4.

Increased variability in strata 1 and 5 was not as concerning because low numbers of fish were moving through the fishway in these strata, in many cases absent of fish movement, resulting in very low estimates of period escapement. If more variability was apparent within peak run times (i.e. 13 May – 25 May 2015) and periods (strata 2 – 4), then the variance of E would increase. Most of the 38 days of the run held estimates of zero for escapement within strata 1 and 5. In the cases for these strata where the estimate was not zero, a higher CV value was calculated. Nelson (2006) states the mean CV across strata often reveals the total precision of the methodology. The high CV values in strata 1 and 5 were balanced by lower CV values in strata 2 – 4 providing a lower overall CV for E.

If this project were to be conducted for future spawning runs, or for previous runs not yet analyzed, it is recommended that the two-way stratified random sampling design remain unchanged. A ~5% confidence interval was achieved for E, and CV values were relatively small for strata 2 – 4 over strata 1 and 5. If hour groupings of strata 1 – 5 were to be changed, grouping lower counts of strata 1 or 5 with the higher counts of strata 2 or

4 may have a drastic effect on variability and, thus, this change should be avoided.

Study Site Enhancements

Using visual counts to assess Alewife spawning escapement required a large emphasis upon visual acuity. For future projects using video and visual counts, the clarity of the video source should be increased. First and foremost, the painted white board below the field of view of the recording device should be replaced and cleaned routinely throughout the duration of the spawning run. During periods of high fish movement, the white board was often useful for distinguishing fish when paired with a reduction in video speed. Replacing and cleaning the board would increase the accuracy of counts.

Secondly, the efficiency of the lighting system should be improved. It would be ideal to increase the lighting brightness and to add regulated lighting correction to account for the natural light, or lack thereof, in day and night hours.

Video Formatting and Compression

Audio Video Interleaved (AVI) is a container format that can contain both video and audio data. Video data contained in an AVI file is encoded and decoded by specific codecs. AVI was advantageous to use as the format for video samples because there are many common codecs and software that can access AVI. However, the acquired AVI files were compressed using codecs with a lossy compression algorithm which resulted in a loss of video information. Increased resolution would allow compensation for times of high fish passage, and a lossless video compression coupled with a suitable video resolution would achieve this goal. Lossless compression may allow particle separation and tracking software to automatically count fish movements, or have suitable resolution to count fish when many are moving through the fishway. Uncompressed videos are extremely large in size compared with lossy compression formats, but more recent

28 lossless video codecs such as Huffy and Lagarith may be available for the current video monitoring systems.

Biological Characteristics

The time series of available data shows this stock has been heavily exploited through the 1990s and early 2000s. U is a major factor of concern; however, the age of the Alewife when they are exploited can also be an important factor in future generations because of differences in spawning yield. Exploitation rates from 1997 – 2001 averaged

80% and targeted Alewife from predominately two age classes. The Alewife U of 2015 was estimated to be 59%, but no age-class information was available. U addresses

Alewife harvest and does not include biological characteristics such as age, sex, size, or condition from either escaped or harvested fish. Sampling a proportion of escaped and harvested Alewife for age, sex, size, and condition would inform managers about the stock. In order to make inferences about stock health, knowledge of the range and proportion of run-specific Alewife age is essential.

Alewife typically spawn five times in their lifetime, and can live for up to ten years. If a larger proportion of first-time spawners are being removed as opposed to older spawners, the yield of future generations will be decreased provided those first-time spawners’ life time egg production exceeds older, and presumably larger, spawners.

Additionally, the ratio of males to females would inform what proportion of females are in the count, and thus, fecundity. Previous assessments have obtained these metrics; however, since 2007, no biological sampling has been conducted. Aside from age and sex, assessing the physiological condition of Gaspereau River Alewife may reveal environmental effectors exerting stress upon the population. Many diseases and

29 physiological conditions obtained by Alewife are coupled with external indicators of fish health, which may be useful in revealing population health.

Recruitment

Recruitment, R, to the Gaspereau River adult Alewife fish stock is able to occur as early as age three, but normally sexual maturity occurs at ages four or five. Full R is reached when all of the offspring are considered vulnerable to fishing, and occurs at age six (DFO, 2007). Related to the fisheries management plan implemented in 2002 and assuming that a proportion of spawned Alewife in this season were pre-maturely recruited

(e.g. sexually immature Alewife at age four in 2006), a resultant increase in Y due to R from this season would not have been observed until 2006. To be able to estimate R, it may be beneficial to introduce escapement and recruitment efficiency as variables in future studies to further define the average age of Alewife R in the Gaspereau River, and to explore any external impacts upon pre-mature Alewife, such as survivability post- spawning. If spawned Alewife from subsequent generations are not progressively recruited from year-to-year, identifying and regulating other external factors may be integral to increasing abundances.

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Table 1. An overview of the main goals set by the implementation of the Gaspereau

River Fisheries Management Plan prior to the 2002 fishing season (DFO, 2007; McIntyre et al., 2007)

Management Plan Objective Management Plan Methodology

Within 5 years: Close 1.8km of river below new fishway to alewife fishing a) Achieve an escapement of 400,000 alewife above the White Rock Provide additional 1 day per week close fishway time (2130h each Tuesday to 0530h each Thursday) subject to on-going review for b) Reduce Fishing Mortality effectiveness

Square nets to be removed from the water and chained and locked during the weekly close times

DFO to provide additional monitoring and enforcement to ensure compliance with all restrictions

Conduct in-season reviews to ensure progress and make necessary adjustments towards achieving the goal

Table 2. A table depicting the selected hour groupings for the period stratum. Three time samples (units) were randomly selected from each period per day.

Stratum Time Period 1 00:00h-06:00h

2 06:00h-12:00h

3 12:00h-16:00h

4 16:00h-20:00h

5 20:00h-24:00h

Table 3. Gaspereau River Alewife (Alosa pseudoharengus) spawning run harvest data including reported landing counts from logbooks measure, the logbook reporting rate and

Fishery Officer pail count estimates from 1986 – 2006 (from McIntyre et al., 2007).

Year Logbook Logbook Fishery Fishery Reported Reporting Officer Pail Officer Pail Catch (metric Rate (%) Count Count tons) Estimates Estimates - # (metric tons) of 50 lb pails 1986 148 209 9,228 1987 130 86 261 11,510 1988 73 71 25 (206) 1,100 (9,087) 1989 200 85 280 12,380 1990 186 41 174 7,679 1991 95 79 64 2,816 1992 45 83 75 3,320 1993 72 92 133 5,886 1994 149 88 182 8,022 1995 171 100 180 7,958 1996 78 100 136 5,999 1997 64 79 115 5,096 1998 61 80 63 2,800 1999 61 77 108 4,772 2000 82 73 139 6,157 2001 11 33 26 1,142 2002 48 81 94 4,130 2003 58 64 112 4,949 2004 23 59 64 2,845 2005 32 63 52 2,314 2006 56 79 66 2,910

Table 4. Mean estimates and standard deviation (SD) of Alewife (Alosa pseudoharengus) escapement for all 5 strata over the 38 days of the 2015 Gaspereau River spawning run.

The maximum mean estimate, 261.5, was on 15 May in strata 4, and the maximum standard deviation, 121.2, was on 20 May in strata 5.

Strata 1 2 3 4 5 Date Mean SD Mean SD Mean SD Mean SD Mean SD 9 May 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10 May 0.0 0.0 0.0 0.0 1.0 1.0 0.3 0.6 0.0 0.0 11 May 0.0 0.0 0.0 0.0 10.3 1.2 11.0 10.4 0.0 0.0 12 May 0.0 0.0 3.7 3.1 18.0 3.5 25.3 1.2 0.7 1.2 13 May 0.0 0.0 32.7 29.1 109.3 35.4 73.2 27.3 5.0 7.8 14 May 2.3 4.0 99.7 35.0 100.2 8.9 143.0 59.6 0.3 0.6 15 May 17.3 14.2 125.3 4.2 129.8 38.9 261.5 78.3 12.0 19.1 16 May 25.7 22.2 168.7 18.5 186.5 33.4 163.3 59.7 44.0 66.1 17 May 0.0 0.0 58.7 17.3 207.7 9.0 140.0 40.0 30.3 26.7 18 May 39.3 65.5 176.7 87.2 207.8 14.9 253.7 59.5 40.2 34.7 19 May 0.0 0.0 191.0 116.8 227.0 64.9 210.9 60.3 29.0 25.7 20 May 12.7 21.9 53.7 42.1 190.4 54.4 224.0 15.7 71.0 121.2 21 May 0.0 0.0 152.7 54.9 90.5 54.0 72.7 9.3 0.3 0.6 22 May 68.3 13.0 85.7 33.0 82.7 55.6 126.0 36.0 30.3 27.6 23 May 0.0 0.0 19.3 10.0 24.3 13.6 26.7 3.8 9.7 15.0 24 May 8.0 7.2 39.3 41.4 94.7 15.1 77.7 24.0 10.3 8.5 25 May 14.0 24.2 138.7 26.6 227.0 27.0 113.0 47.8 12.0 19.1 26 May 13.8 24.0 91.8 23.5 79.8 65.6 199.0 120.2 3.7 6.4 27 May 24.3 42.1 174.7 4.0 155.3 25.1 93.8 18.3 4.7 4.7 28 May 0.0 0.0 94.2 53.3 128.3 33.1 51.3 18.0 16.0 13.9 29 May 5.8 10.1 53.7 17.5 56.0 9.5 30.0 23.4 2.3 4.0 30 May 0.0 0.0 30.8 22.4 30.7 12.2 19.0 5.2 0.3 0.6 31 May 0.0 0.0 24.7 20.4 25.8 16.3 20.7 25.6 1.7 2.9 1 June 1.0 1.7 23.7 23.7 160.5 10.1 29.0 17.1 24.0 5.6 2 June 4.0 6.9 10.7 8.5 13.7 2.3 7.3 4.5 0.7 1.2 3 June 0.0 0.0 0.3 0.6 0.7 1.2 12.7 3.1 10.0 3.0 4 June 2.0 3.5 0.0 0.0 12.3 11.6 42.0 15.1 0.3 0.6 5 June 0.0 0.0 8.3 3.8 24.0 7.0 19.0 12.1 5.7 9.8 6 June 0.7 1.2 7.7 11.0 12.7 15.9 14.7 8.4 5.0 8.7 7 June 0.0 0.0 2.3 2.5 9.0 10.6 6.3 2.5 0.0 2.0 8 June 2.0 2.0 19.7 10.6 22.3 9.3 10.3 2.5 1.0 1.0 9 June 0.0 0.0 29.0 11.5 41.8 10.9 27.7 26.7 3.0 4.4 10 June 0.7 1.2 37.7 11.4 25.0 13.1 3.0 2.6 4.7 8.1 11 June 0.3 0.6 17.0 10.4 16.0 10.5 20.7 2.3 7.0 11.3 12 June 0.0 0.0 25.0 18.7 12.3 4.5 8.7 3.8 0.0 2.0 13 June 0.0 0.0 12.3 10.0 5.3 5.9 4.3 2.1 9.7 9.1 14 June 0.0 0.0 5.0 7.0 3.7 3.1 3.0 3.6 0.0 0.0 15 June 0.7 1.2 6.3 6.1 7.7 6.4 10.0 4.6 6.7 11.5

Table 5. Compilation of annual logbook recordings and catch estimates from Gaspereau fishermen and estimates of escapement, run size and exploitation rate over 15 years from

Year Reported Catch Escapement Estimated Exploitation Log Estimate Estimate Run Size Rate (%) Book (number (number Catch of fish) of fish) (kg) 2015 145,355 623,755 *436,879 ± 1,060,634 58.8 24,230 2006 56,053 282,589 *209,064 ± 491,653 57.5 35,540 2005 31,558 219,173 *265,705 ± 484,878 45.2 39,855 2004 22,605 268,820 *175,046 ± 443,866 60.6 17,504 2003 58,227 416,335 *435,832 852,167 48.9 2002 47,899 391,278 310,746 702,024 55.7 2001 10,947 119,348 238,842 358,190 33.3 2000 82,066 754,585 98,883 852,468 88.4 1999 61,067 698,600 81,326 779,926 89.6 1998 61,304 372,400 171,639 544,039 68.5 1997 63,472 611,520 95,443 706,953 86.5 1995 170,775 954,960 126,933 >1,081,892 <88.3 1984 212,966 111,100 324,066 65.7 1983 150,408 114,800 265,208 56.7 1982 254,068 50,400 304,468 83.4 1970 480,000 60,527 540,527 88.8

Minas S

Basin

Bay of Fundy Sh

C G A

Figure 2. The five major river systems that empty into the Minas Basin; Cornwallis River

(C), Gaspereau River (G), Avon River (A), Shubenacadie River (Sh) and the Salmon

River (S).

C Bay of Fundy

Gaspereau River

Figure 3. The Bay of Fundy splitting into two regions, northeast Chignecto Bay (C), and

Minas Basin (M). The marking indicated the location of the Gaspereau River, Kings

County, Nova Scotia, at 45.12°N, -64.27°E, and its proximity to the Minas Basin.

Figure 4. A longitudinal view of the new concrete White Rock fish ladder, built in 2002.

Figure 7. A jitter plot showing the comparison between estimates of total escapement between the 5 defined strata during the Gaspereau River, NS, Alewife (Alosa pseudoharengus) spawning run from 9 May – 15 June 2015. Larger estimates were apparent during high movement mid-day periods (strata 2 – 4). Lower estimates were observed during periods of low fish movement (strata 1 and 5). Maximum mean daily estimate was 261, which was observed on 15 May, for stratum 4 (Table 4).

Figure 9. A bubble plot showing the ratio between the standard deviation and the mean,

CV, for the number of Alewife (Alosa pseudoharengus) estimated to have ascended the

White Rock fish ladder on the Gaspereau River, NS, by day and by strata, from 9 May –

June 2015. Day 1 is the first day of the run, 9 May, and day 38 is the last day of the run,

15 June. Higher mean counts were observed during mid-to-late May.

Figure 11. Estimates of Alewife (Alosa pseudoharengus) escapement taken at the White

Rock fish ladder from 14 years of Gaspereau River, NS, spawning runs from 1983 –

2015. Escapement estimates from 1983 – 2006 were obtained from McIntyre et al (2007).

Figure 13. Estimated Alewife (Alosa pseudoharengus) exploitation rates from 14 years of Gaspereau River, NS, spawning runs from 1983 – 2015. Exploitation rates from 1983

2006 were obtained from McIntyre et al (2007).

Spawning escapement critical cautious healthy

2.0

1.5

over

exploited

RLL 1.0

U/U

fully

exploited

Exploitation rate Exploitation 0.5

partially

exploited

0.0

0.0 0.5 1.0 1.5 2.0 Esc/EscUSR U URR = 0.53 Gaspereau River U fully = 0.35 Alewife Esc USR = 4e+05 Esc LRP = 234549

Figure 14. Assessment summary showing the status of the Gaspereau River, NS, Alewife

(Alosa pseudoharengus) stock and commercial fishery relative to reference levels for fishing mortality rates and spawning escapements used to assess the status of the stock.