Section 1.G Evaluation of the needs of other Wildlife Species

Section 1.G Evaluation of the needs of other Wildlife Species

in projects developed by Ducks Unlimited Canada

Fish Use of a Marsh Managed for Waterfowl and a Natural Marsh

on the Ottawa River

by

Serge Pépin Cécile Dubé

and Claude Grondin

Quebec City, March 1994

Gouvernement du Québec

Ministère de l'Environnement et de la Faune Direction de la faune et des habitats

Canards Illimités Canada Unlimited Ducks Canada

Reference for this publication:

PÉPIN, S., C. DUBÉ and C. GRONDIN. 1994. Fish Use of a Marsh Managed for Waterfowl and a Natural Marsh on the Ottawa River. Protocol Agreement concerning a Five—Year Plan for the Protection and Development of Wildlife Habitats. Section IG. Ministère du Loisir, de la Chasse et de la Pêche du Québec and Ducks Unlimited Canada, Quebec. 154 p.

ABSTRACT

The objective of this study was to characterize and assess the fish population and fish response in a managed marsh compared to a natural marsh. Study areas were described, fish populations were determined and aspects of the dynamics of young—of—the—year populations were documented.

The study areas, located on the North shore of the Ottawa River in Québec, included Massettes Marsh, a managed area with controlled water levels maintained by dykes since 1978, and Daragon Bay, a natural marsh. Massettes Marsh does not provide fish with free access to the Ottawa River except during flooding, while Daragon Bay is aiways in contact with the river. Vegetation types in both marshes is similar, although emergent and floating—leaf vegetation cover a larger surface area In Massettes Marsh than in Daragon Bay. Submergent vegetation, however, Is more abundant in the unmanaged marsh. High water temperatures and low dissolved oxygen levels were observed in both areas. The average water level fluctuations during summer were 35 cm in Daragon Bay while Massettes Marsh water levels were relatively stable.

Fish sampling revealed good species diversity in each study area, with vine species observed in Massettes Marsh and twelve species observed in Daragon Bay. The most represented species included: Brown Bullhead, Pumpkinseed, Yellow Perch, Golden Shiner, Black Crappie, Central Muciminnow and Northern Pike. Muskellunge, Rock Bass and Largemouth Bass were observed in Daragon Bay only.

In Massettes Marsh, the population of adult and juvenile fish over one year old was estimated at just over 10 000, while the population of young—of—the—year was estimated at approximately 1 000 000.

A greater proportion of adults was captured in Daragon Bay compared to Massettes Marsh. At every developmental stage, Brown Bullhead was the most abundant species in both marshes. The survival rate of young Brown Bullhead,

from the time eggs are laid to the end of summer, is estimated at better than 10 % for the managed marsh for most fish species, the growth pattern of young—of—the—

year was found to be similar in both study areas.

A predictive model to estimate productivity was developed which can be applied to habitat conditions similar to those found in Massettes Marsh. This model uses influencial factors which are easy to measure and can, therefore, provide population estimates of young—of—the—year at a reasonable cost.

TABLE OF CONTENTS

Pape

ABSTRACT il I

TABLE OF CONTENTS

LIST OF TABLES vii

LIST OF FIGURES xi

LIST OF APPENDICES xii

1. INTRODUCTION 1

1.1 Problem and purpose of the study 1

2. it/IATERIALS AND METHODS 4

2.1 Study areas 4

2.2 Distribution of sampling activities 6

2.3 Characterization of environments 9

2.3.1 Plant coverage 9

2.3.2 Physical and chemical characteristics 11

2.4 Use of marshes by fish 13

2.4.1 Use by adults and juveniles over a year old 14

2.4.2 Use by young—of—the—year 20

2.4.3 Model for estimating young—of—the—year populations 22 2.5 Analysis of certain aspects of the dynamics of

young—of—the—year populations 27

2.5.1 Survive, rate of Brown Bullhead

young—of—the—year in the managed marsh 27 2.5.2 Growth of young—of—the—year in

the two marshes 29

3. RESULTS AND DISCUSSION 30

3.1 Characterization of environments 30

3.1.1 Habitat categories 30

3.1.2 Plant coverage 31

3.1.3 Physical and chemical characteristics 36

3.2 Use of marshes by fish 58

3.2.1 Species and sizes encountered 58

3.2.2 Use by adults and juveniles over a year old 61

3.2.3 Use by young of the year 79

3.2.4 Model for estimating young—of—the—year populations 90

TABLE OF CONTENTS

Page

3.3 Comparison of the two environments 97

3.3.1 Plant coverage 97

3.3.2 Physical and chemical characteristics 104

3.3.3 Fish species 106

3.4 Analysis of certain aspects of the dynamics of

young—of—the—year populations 109

3.4.1 Survival rate of Brown Bullhead

young—of—the—year in the manage! marsh 109 3.4.2 Growth of young—of—the—year in the

two environments 111

4. CONCLUSION 121

ACKNOWLEDGEMENTS 124

LIST OF REFERENCES 125

APPENDICES 128

LIST OF TABLES

Pape Table 1. Fishing effort using gillnets in Daragon Bay in 1989 19 Table 2. Physical and chemical characteristics of the charmais

of Massettes Marsh in June and early July 1989 37 Table 3. Physical and chemical characteristics of the charmais

of Massettes Marsh in late July and August 1989 38 Table 4. Physical and chemical characteristics of the channels

of Massettes Marsh in October and early November 1989.. 39 Table 5. Physical and chemical characteristics of the shallow

part of Massettes Marsh In June and early July 1989 40 Table 6. Physical and chemical characteristics of the shallow

part of Massettes Marsh in late July and August 1989 41 Table 7. Physical and chemical characteristics of the shallow

part of Massettes Marsh in November 1989 42 Table 8. Total and partial correlations between the variables used

In multiple regression plane equations explaining variations in dissolved oxygen in the shallow part of

Massettes Marsh in Summer 1989 45

Table 9. Physical and chemical characteristics in Daragon Bay

In June 1989 50

Table 10. Physical and chemical characteristics in Daragon Bay

in August 1989 51

Table 11. Physical and chemical characteristics in Daragon Bay

In October 1989 52

Table 12. Variations in water level in Daragon Bay from

June to October 1989 53

Table 13. Total and partial correlations between the variables used in multiple regression equations variations in

dissolved oxygen in Daragon Bay in Summer 1989 56

LIST OF TABLES (conte)

Page Table 14. Catch of adults and juveniles over a year old per

unit of fishing effort (seine trap) in the channels of

Massettes Marsh in June 1989 63

Table 15. Catch of adults and juveniles over a year old per unit of fishing effort (seine trap) In the channels of

Massettes Marsh in August 1989 64

Table 16. Catch of adults and juveniles over a year old per unit of fishing effort (small fyke net) in the shallow

part of Massettes Marsh in August 1989 65 Table 17. Estimated population of Northern Pike (Esox lucius)

adults and juveniles over a year old living in the

charmais of Massettes Marsh in August 1989 68 Table 18. Estimated population of Pumpkinseed (Leoomis pjbbosus)

adults and juveniles over a year old living in the

channels of Massettes Marsh in August 1989 68 Table 19.

Table 20.

Estimated population of Golden Shiner (Notemiaonus crvsoleucas) adults and juveniles over a year old

living in the channels of Massettes Marsh in June 1989 ... 69 Estimated population of Golden Shiner (Notemigonus

crvsoleucas) adults and juveniles over a year old

living In the channeis of Massettes Marsh in August 1989.. 69 Table 21. Estimated population of Brown Bullhead (Ictalurus

nebulosus) adults and juveniles over a year old

living in the channels of Massettes Marsh in June 1989 70 Table 22. Estimated population of Brown Bullhead (Ictalurus

nebulosus) adults and juveniles over a year old

living in the channels of Massettes Marsh in August 1989 . 71 Table 23. Estimated population of Black Crappie (Pomoxis

niaromacuiatus) adults and juveniles over a year old living in the channels of Massettes Marsh

in June 1989 72

LIST OF TABLES (conte)

Paae Table 24. Estimated population of Black Crappie (Pomoxis,

niaromaculatus) aduits and juveniles over a year old living in the channels of the Massettes Marsh

in August 1989 72

Table 25. Estlmated population of Yellow Perch (Perca flavescens) aduits and juveniles over a year old

living in the channels of Massettes Marsh in June 1989 73 Table 26. Estlmated population of Yellow Perch (Perm

fiavescens) aduits and juveniles over a year old living

in the channels of Massettes Marsh in August 1989 73 Table 27. Catch of adults and juveniles over a year laid per

unit of fishing effort in Daragon Bay in June 1989 75 Table 28. Catch of adulte and juveniles over a year old per

unit of fishing effort in Daragon Bay in August 1989 76 Table 29. Catch of adulte and juveniles over a year old per

unit of fishing effort in Daragon Bay In October 1989 77 Table 30. Catch of young—of—the—year per unit of fishing effort

(seine trap) in the channels of Massettes Marsh

in August 1989 80

Table 31. Catch of young—of—the—year per unit of fishing effort (small fyke net) in the shallow part of Massettes

Marsh in August 1989 81

Table 32. Estlmated population of young Brown Bullhead (Ictaturus nebulosus) of the year living in Massettes

Marsh in August 1989 83

Table 33. Estimated population of young Carp (Cvarinus carpio)

of the year living in Massettes Marsh in August 1989 84 Table 34. Estimated population of young Yellow Perch (Perca

flavescens) of the year living in Massettes Marsh

in August 1989 85

LIST OF TABLES (conta.)

Pace Table 35. Catch of young of the year per unit of fishing effort

in Daragon Bay in June 1989 87

Table 36. Catch of young of the year per unit of fishing effort

in Daragon Bay in August 1989 88

Table 37. Catch of young of the year per unit of fishing effort

in Daragon Bay in October 1989 89

Table 38. Total and partial correlations between the variables used in multiple regression plane equations explaining variations in catch per unit of effort (CPUE) of young Brown Bullhead (Ictalurus nebulosus), Carp (Cvprinus caroiq) and Yellow Perch (Perce flavescens) of the year in the shallow part of Massettes Marsh

in Summer 1989 91

Table 39. Estimated population of young Brown Bullhead (Ictalurus nebulosus) of the year obtained from the predictive model and parameters measured at

different stations 98

Table 40. Estimated population of young Carp (Cvprinus carpio) of the year obtained from the predictive model and

parameters measured at different stations 100 Table 41. Estlmated population of young Yellow Perch (Perce

flavescens) of the year obtained from the predictive

model and parameters measured at different stations 102 Table 42. Estimate of average weight, fertility and number

of females and mature females and production (number of eggs released) by 10—mm length class in Brown Bullhead (Ictalurus nebulosus) in Massettes

Marsh in 1989 110

LIST OF FIGURES

Page Figure 1. Geographic location of study areas and development

phases of Massettes Marsh 5

Figure 2. Illustration of Daragon Bay marsh 7

Figure 3. Location of sampling stations in Massettes Marsh in 1989 . 8 Figure 4. Location of sampling stations in Daragon Bay in 1989 10 Figure 5. Illustration of a seine trap used to catch fish in the

channels of Massettes Marsh in 1989 15

Figure 6. Example of type of distribution of catch per unit of effort (CPUE) obtained in seine trap: distribution of frequency of catch of Yellow Perch (Perca flavescens) with a seine trap in the channels of Massettes

Marsh In August 1989 16

Figure 7. Scatter diagrams of dissolved oxygen concentration based on the parameters selected for multiple regression models to explain variations in this parameter in the shallow part of Massettes Marsh in

June and August 1989 46

Figure 8. Scatter diagrams of dissolved oxygen concentration based on the parameters selected for multiple regression models to explain variations in this

parameter in Daragon Bay in June and August 1989 55

Figure 9. Scatter diagrams of catch per unit of effort of young Brown Bullhead, (ictalurus nebulosus) Carp (Cvprinus carojo) and Yellow Perch (Perca flavescens) of the year based on the parameters selected for multiple regression plane equations to explain variations in the abundance

of these fish in Massettes Marsh in Summer 1989 92 Figure 10. Growth in Iength of young—of—the—year of ail eight fish

species in Massettes Marsh and Daragon Bay in 1989 . . .. 112

LJST OF APPENDICES

Paae Appendix 1. Characteristics of plant coverage in the shallow part

of Massettes Marsh in Summer 1989 131

Appendix

2.

in June 1989 136

Appendix 3. Characteristics of plant coverage in Daragon Bay

in August 1989 139

Appendix 4. Histograms of sizes in different species of fish caught

in Massettes Marsh in Summer 1989 142

Appendix 5. Histograms of sizes in different species of fish caught

in Daragon Bay in June, August and October 1989 146

1. INTRODUCTION

The ecological importance of wetlands is receiving increasing recognition. Apart from the raies they play in regulating and cleaning water and in purifying the atmosphere, these areas are the most productive of all naturel environments (Lavoie 1984; Grondin 1988). The abiotic and biotic diversity found in wetlands is such that no other biotope offers similar support for plant and animal lite.

Wetlands in Quebec occupy approximately 15% of the land area and are under heaviest use by waterfowl and fish between March and November (Grondin 1988).

The life cycles of a number of fish of economic interest are closely linked to wetlands. Provost (1981) mentions that 28 fish species in the southwestern part of the province find conditions appropriate for reproduction and the growth of fry in these environments. Wetlands thus generate and export to adjacent streams the biomass needed te maintain many of our fish populations.

1.1 Problem and purpose of stuck

Construction of the Carillon Dam in 1963 transformed a number of areas along the Ottawa River into wetlands (Munro 1967). In 1976, Dues Unlimited Canada (DU) undertook to develop some of these wetlands to encourage waterfowl production.

There were three types of development (Grondin 1988):

1. digging long, narrow channels to increase free water surfaces in areas of dense emergent vegetation

2, creating small artificiel islands to act as refuges agaInst predators and flooding

3. dyking marsh to retain part of the spring flood waters throughout the year

A number of studies have nevertheless shown that the latter type of development creates obstacles for fish in the Ottawa River (Desjardins and Thellen 1980;

Chabot and Fournier 1985; Dion 1986; Pépin et al. 1990; Macquart et al. 1990;

Langevin 1990). ln addition to blocking access by fish, whose migration to spawning grounds does not correspond to the flood period, the dykes imprison spawners, which are obllged to remain in the developed site with their offspring.

The survival of these fish is then endangered by extreme temperature and oxygen conditions that may occur during the summer and under the ice cover, as weli as by deep freezing during the winter.

To achieve optimum wetlands development design and management, DU and the Quebec Department of Recreation, Fish and Game (MLCP) have undertaken to assess the use of managed marshes by fish, estimate the impact of waterfowl management and matie any needed tests of corrective measures and new development and management concepts.

The first phase of testing in the summer of 1988 resulted in definition of the sampling techniques best suited to survey fish in these environments and study the composition of the fish community using dyked marshes (Pépin et al. 1990).

The second phase, which look place in 1989, provided an assessment and comparison of the use of a dyked marsh (Massettes Marsh) and a natural marsh (Daragon Bay) by fish. The goals of this study wers to:

1. define how the two types of environment are used by fish

2. assess the abundance of adult fish using these marshes

3. assess the abundance of young-of-the-year produced in these environments

4. characterize and compare certain aspects of the dynamics of young-of-the- year populations produced in these two environments

Fuifilment of these objectives wouid enable us to assess the benefits and lasses in renewable resources resulting from DU development and then study corrective measures and management plans for optimum development.

2. MATERIALS AND METHODS

2.1 Study areas

The two study sites are located on the north shore of the Ottawa River near the village of Thurso, 40 km east of Hull and 125 km west of Montreal (Figure 1). The land adjacent to the marshes is mainly used as pasture. The soil is made up of a layer of organic matter and alluvial deposits covering a marine clay base (Oxley et â. 1985).

Manaaed marsh

Massettes Marsh (45°34' N., 75°16' W.) is bordered by Route 148, Lochaber Bay and the Ottawa and Blanche rivers.

This area was developed three times between 1976 and 1978 (Figure 1). Artificial islands and long channel systems were built near Route 148, and then the marsh was dyked. The dyked part covers 83.9 hectares, of which about 70% romains under water during the low—water period (readings taken by DU in 1987).

Massettes Marsh may be in contact with the Ottawa River between March and May, during the spring floods. Over the past twelve years, contacts occurred mainly in April, when the water level rose above the control structure, the spillway or the lowest part of the dyke; however, the water level topped the average height of the dyke only once.

Naturel marsh

Daragon Bay (45°35' N., 75°16' W.) is located 600 metres east of Massettes Marsh (Figure 1). It ls bordered by the Blanche River on the east, the Ottawa on the south and by farmiand to the north.

The area of the marsh is 30.7 hectares during low water in August, and 31.7 hectares in June and October. The marsh is in permanent contact with the Ottawa River through a 160—metre opening in the central part and a smaller,

OttOWCI

STUDY SITES MI : Developed in 1976

NI I I : Developed in 1977 Mill Developed In 1978

Figure 1. Geographic location of study arecs and development phases of Massettes Marsh.

10—metre opening in the pond on the east side (Figure 2). It also communicates with the Blanche River in the spring through a 50—metre opening. The marsh is almost entirely under water in the spring, while in August a central strip between the eastern and northern ponds is dry and covered with vegetation up to a point 80 metres from the Ottawa River. The 80—metre section out to the river romains under water.

2.2 Distribution of samplina activities

Manaoed marsh

Although work on the dyked part of Massettes Marsh in 1989 extended from May 22 to November 10, this report deals mainly with the methods used and results obtained during the period from July 24 to August 25, although data collected outside this period may also be mentioned.

Sampling stations were installed systematically along the dyked part of the marsh.

In the shallow part, they were placed along 15 parallel transects 100 metres apart, with one station every 50 metres. In the channels, one station was set up every 100 metres. In ail, 135 stations were set up in the shallow marsh and 26 in the channels (Figure 3).

Naturel marsh

Three 10—day sampling campaigns were conducted in 1989, from June 5-16, August 7-18 and October 23—November 3.

Three north—south transects were positioned using a rational choice strategy. The first crossed the west and north ponds of the marsh, the second cut across the central part and the third crossed the east pond. A maximum number of stations were systematically distributed along each transect, 100 metres apart except for

• Station, main channel

. 1_\

Station, small channel Station, shallow marsh

Figure 3. Location of sampling stations in Massettes Marsh in 1989.

Transect III, where the short distance covered meant that one station had to be Iocated 50 metres from the previous one. In the first 100 metres of each transect, one station was sampied with a gillnet (Figure 4). Location of the stations varied from one sampling period to another because of fluctuations in water love', In June, there were seven stations on Transect 1, four on Transect 11 and three on Transect III, for a total of 14. The decrease In water surface in August removed three stations from the central part (11-2. 11-4,11-6) and one from Transect 1(1-12).

To compensate for this, stations 111-2A and III-2B were placed In the east pond, (based on water depth), where there were only three stations. Thus, 12 stations were sampled In August. Similarly, in October, stations 1-10 and 11-2 could not be used. A new station (11-1) was set up in the flooded part of Transect 11, 25 metres from the Ottawa River.

2.3 Characterization of environments

The same criterla were used to characterize the managed marsh and the natural marsh.

2.3.1 Plant coverage

In Massettes Marsh, characterization of plant coverage took place from mid—June to early July. This was done within a 10—metre quadrant every 100 metres in the shallow marsh. In the natural marsh, plant coverage was characterized In the spring (June) and summer (August). Each sampling station in the natural marsh also covered 100 m2.

Plant coverage was characterized in three stages:

1. assessment of the percentage coverage by all emergent and floating macrophytes

oe , H,..d...„.„

- 00

r Transect number .0 Station number na Direction of gilinets

cZ>

z n III

Ottawa River

o Vie m

1 . • I

Figure 4. Location of sarnpling stations in Daragon Bay in 1989

2. Calculation of percentage coverage by emergent, floating and submerged strata.

3. Identification of the main species making up the three strata and assessment of their relative importance.

In the managed marsh, an additional parameter called "accessibility" was evaluated. This parameter, mainly based on the quantity of vegetation and other types of obstacles (earth, tree trunks) around a station, gives an assessment of the degree of isolation and thus the difficulty of access for fish. Accessibility is calculated by assigning a rating from 1 to 10 to the station based on the following scale:

Rating Percentage accessibility

1 1 to 10%

2 11 to 20%

3 21 to 30%

4 31 to 40%

5 41 to 50%

6 51 to 60%

7 61 to 70%

8 71 to 80%

9 81 to 90%

10 91 to 100%

2.3.2 Phvsical and chemical characteristics

Depth, air temperature, water temperature, dissolve oxygen, pH and conductivity were measured at 68 stations in the managed marsh, i.e. at the 26 stations located in the channels and every 200 metres in the shallow marsh. In the natural marsh, these parameters were assessed (with the exception of air temperature) at ail stations, in Blanche River and the Ottawa River. Two identical sets of measurements were made at each station and where there was sufficient depth

(in channels and certain stations in the natural marsh), samples were taken at two levels, near the surface and close to the bottom. As well, transparency was measured with a Secchi disk in the channels of Massettes Marsh, at each station in the natural marsh and ln the rivers bordering Daragon Bay.

Dissolved oxygen is a critical factor for the survival of fish in the managed environment during the summer. To better understand the dynamics of this factor, we sought among the parameters measured those that might explain the variations in oxygen in the managed environment during the summer. The parameters examined were:

lime of dav

Pépin et al. (1990), mention that photosynthesis caused dissolved oxygen in wetlands to increase gradually as the day progressed.

Percentaqe of free water at the station

The area free of vegetation is important from two points of view. lt promotes gas exchanges between the water and the ambiant air and allows light to penetrate into the water and provide energy for the submerged plants that are mainly responsible for oxygen production in this environment.

Percentaqe of submeraed plants

This category of macrophytes is the most important for oxygen production in the aquatic environment. The quantity of dissolved oxygen in a given location might then be linked to the abundance of submerged plants at that location.

Accessibility

Isolation of a station in an area of abundant vegetation may influence the quantity of dissolved oxygen in the area by creating a wind break and Chus limiting exchanges with the amblent air.

Water temperature

It is well recognized that the quantity of dissolved oxygen in water is closely linked to temperature.

Independent and significant parameters were used to calculate multiple regression plane equations to explain most of the oxygen variations in the shallow part of Massettes Marsh and in Daragon Bay in ,dune and August.

2.4 Use of marsheq by fish

Three types of data were used to evaluate use of the managed and natural environments by fish:

1. Qualitative data (observations) were used to define the types of use.

2. Seml-quantitative data (catch per unit of effort) were used to estimate the relative abundance of specles and sizes and characterize community structures.

3. Quantitative data (population estimates) were used to assess the absolute abundance of species and sizes.

2.4.1 Use by adults and luveniles over a vear old Manaaed marsh

Observation of the movements, behaviour and degree of maturity of aduit fish enabled us to identify the species that corne to spawn in the managed marsh.

Pépin et al. (1990) demonstrated that, following the spawning period, adults of the main species using Massettes Marsh are concentrated in the channels. For this reason, a sampling strategy aimed at estimating the abundance of these fish when grouped in this type of habitat was adopted.

The principle of the method is to estimate the average number of fish in a Cyan area of the channel, so as to be able to extrapolate the absolute abundance for ail channels. Sampling was carried out in the 26 stations along the channels, using a 45 m2 seine trap (Figure 5) of 5—mm stretched mesh. The seine trap was installed the Wight before and loft in the raised position until the next moming. It was thon Iowered taking cane not to frighten the fish undemeath. The fish thus imprisoned were thon removed, doing three sweeps Inside the seine trap using a haui seine with a bag, A fourth sweep was made using the seine itself. The aduit fie and juveniles over a year old thus caught were identified, counted, measured, weighed, and thon marked by clipping fin and released. The fish were marked in order to recognize individuals already caught at another station and thus exclude them from the recuits (as if the 26 stations had been fished simultaneously) and to validate the population estimates obtained using this method by a Petersen type mark—recapture test carried out after the sampling in seine trap.

Catches in seine trap are census variables. They express a number of entities per sampling unit. Like many census variables, catch per unit of effort is distributed asymmetrically on a negative binomial distribution (Figure 6). This probability model is particularly well suited to phenomena of a contagious nature, which means that the aclult fish and juveniles over a year old living in the channels

Figure 5. Illustration of a seine trap used to catch fish in the channels of Massettes Mare in 1989.

12

N282

10 r

FREQUENC Y OBSER VED

N [ri "a- LOI CO N CO Cr) Q Y7

" ve0

CPUE—SEINE TFIAP/PEFIJAUG.

Figure 6. Example of type of distribution of catch per unit of effort (CPUE) obtainecl in seine trap: distribution of frequency of catch of Yellow Perch (Perca flavescens) with a seine trap in the channels of Massettes Marsh ln August 1989.

17

of Massettes Marsh have a gregarious behaviour. Population estimates for each specles and each 10—mm length class were calculated using catch per seine trap, following the procedure described in Scherrer (1984):

The first step is to calculate the fraction of the area sampled by ail seine traps (fS) and by one seine trap (fs):

fS = total area sampled / total area of channels

fs=

We next calculate the average catch per seine trap () and the confidence interval of this average using the following formulas:

n

= E 1 = 1

catch in the n seine traps / n

2 t a /2

-5+ t

S2C t2 a /2 2

n 4n

2n

The estimate of population (N) and the applicable confidence interval are obtalned as follows:

N = Cifs

Confidence interval of N = Confidence interval of C / fs

The population estimates (N) provided by the Petersen mark—recapture test were calculated using the Bailey (1951) adjusted formula:

A = M(C+1)/(R+1) where M = number of fish marked.

C = sample taken to estimate population.

R = number of flsh marked In sample.

The confidence interval of N was obtained by considering R as a Poisson variable, calculating the confidence interval using the formula:

R+ 1.92± 1.961/747- 1

and substituting for R in the formula for estimating N the values of the upper and Iower limits of that confidence interval (Ricker 1975).

Natural marsh

Only relative abundances (catch per unit of effort) were obtained in Daragon Bay, given the constant exchange between the fish stocks of this marsh and those of the Ottawa River. The observations made during sampling enabled us to define the ways this environment was used by the various species.

Several fishing methods were tested given the variations in habitats found In the natural environment. The fishing gear used included: small fyke net (5.2 m long, 0.45 m high, 10—mm stretched mesh), experimental gillnet (46 m long, 1.8 m high, 25,38,51,64,76 and 102 mm stretched mesh), seine (30 m long, 1.8 m high, 5 mm stretched mesh) and electrofishing with the Copp (1987) method using modified electrodes (Dumont et al. 1988).

Gilinets were used for the first 100 metres of each transect, as close as possible to the Ottawa River. This was mainly for the purpose of observing fish movements between the marsh and the Ottawa River. Fishing effort varied from one station and one sampling campaign to another (Table 1). The fish caught were counted, identified and measured (overall length).

STATION JUNE AUGUST OCTOBER

no. nets effort beetend no. nets effort begin/end no. nets effort begiVend

1-0 1 21:20 12:40/10:00 1 16:50 16:45/9:35 1 18:40 16:50/11:30

1 4:30 12:00/16:30 1 5:15 11:15/16:30

11-0 1 14:15 18:15/8:30 0.5' 18:05 16:15/10:20

2 8:30 9:45/18:15 03 4:45 11:00/15:45

111-0 1 12:55 19:35/8:30 32 17:25 17:55/11:20 2 17:30 16:15/9:45

1 16:30 16:30/9:00 3 3:10 14:00/17:10 2 5:15 10:15/15:30

1 10:45 8:45/19:30

1: Only the 25, 38 and 51 mm mesh was fished norrnally, the remainder of the net being in a very shallow area with dense vegetation.

2: Two 46-metre nets with 25-102 mm mesh and one 23-metre net with 64, 76 and 102 mm mesh.

The choice of other fishing gear depended mainly on water depth and the amount of vegetation. Fyke nets were laid for an average of 20 hours at six stations in June and nine stations in August and October. The fish caught were identified and measured. In August and October, they were also weighed. In June, sevenstations measuring 10 metres by 10 metres were sampled using a seine. In August, three stations were fisheci using the seine trap technique used in the managed marsh. Electrofishing was used at 11 stations in June and eight stations in August. The fish caught by these two methods were also counted, identified and measured.

2.4.2 Use bv vOuna of the vear

Manaded marsh

The abundance of young—of—the—year was caiculated on the basis of experimental fishing with a small fyke net (5.2 m long, 0.45 m high, 10 mm stretched mesh). This gear proved effective in catching young—of—the—year in wetlands and couid be used in various habitats (Pépin et al. 1990). For Golden Shiner (Notemicionuq crvsoleucas), Black Crappie (Pomoxis niaromaculatus), Pumpkinseed (Lepomis pibbosus) and Central Mudminnow (Umbra °n'y relative abundance was calculated due to the very small population density or very small size of individuals which made it difficult to manipulate and mark them. For Brown Bullhead (ictalurus nebulosUs), Carp (Cyprinus carpio) and Yellow Perch (Perce flavescens), relative and absolute abundance were estimated. The absolute abundance of these species was obtained through a two—stage Schnabel mark—

recapture procedure:

1. Considering the large area of the managed marsh, the goal of the first phase, which Iasted three weeks, was to mark a large number of fish in ail parts of the marsh. To achieve this, fishing with small fyke net for an average time of 19.3 hours was carried out every 100 metres in the shallow marsh (68 stations) and the fry caught ln the channels using seine trap were also used. The fish were marked by ablation of fins (dorsal for Brown Bullhead, pelvic for Carp and

Yellow Pare) and the wounds caused by marking were swabbed with malachite green (100 ppm) to limit fungal infections. During this first stage, 24,698 Brown Bullhead, 2,874 Carp and 571 Yellow Perch were marked and released in the marsh.

2. The second phase of the procedure is to make population estimates. For this, 10 experimental fishing stations of the possible 135 in the shallow marsh were designated daily from a random number table. This operation lasted vine days. For a more uniform distribution of fishing effort, only one station per transect was fished each day. As well, seines were cast at random in the channels to increase the catch of young—of—the—year and cover this portion of the marsh. During the survey catches and recaptures were counted and the unmarked fish were marked before being released. This second stage gradually brought to 48,334 Brown Bullhead, 5,506 Carp and 1,294 Yellow Perch the number of fish marked. Every day, a population estimate (N) for the three species involved was calculated based on the total catch for aIl gear, using the following formula (Schnabel 1938):

t t

N= E CtMt / E (Rt) + 1 i = 1 i 1

where Ct = catch on day t

Mt= number of frsh marked and alive at start of day t Rt = recaptures on day t

The confidence Intervals of the population estimates using the Schnabel method are obtained in the same way as with the Petersen method, replacing Rt in the estimation formula by N, by using the upper and lower limit values of the confidence interval (Ricker 1975).

Natural marsh

Young-of-the-year and adults were sampled simultaneously. The count of fry present in June (caught using only a seine) was, however, approximate, since many of them were too small and were not caught in the fishing gear.

2.4.3 Model for estimatinq vouno-of-the-vear populations

Estimating young-of-the-year populations by mark-recapture is hard and costly work. In wetlands, the difficulty of making such estimates is even greater, so it seemed important to use the results obtained during operations in 1989 in Massettes Marsh to construct a simplified mode' for young-of-the-year population estimates that would be applicable in other managed environments with out having to mark and recapture the fish.

Princiole of the model

The model used is taken from Verdon (1979). h use is based on knowledge of two parameters: catch per unit of effort (CPUE) with a given type of gear (small fyke net in our study) and catchability (q), defined as the fraction of the population caught per unit of effort with this type of gear. The population estimate is obtained using the following equation:

N = CPUE/q

Development of the model

The model begins with a population estimate (N) based on a mark-recapture test.

CPUE and N are then used to calculate q:

q = CPUE/(NiS)

where (N/S) is population density (population estimate/area), used in preference to N since the fraction of the population caught per unit of effort depends much more on the number of fish per unit of surface than the absolute quantity of fish in the marsh.

The main problem encountered in calculating q is the great variation in CPUE over time and space. Verdon (1979) mentions that it is not rare to find a situation where the standard deviation of CPUE is greater than average. Part of this variation is due to chance and the behaviour of fish (e.g. fry moving about in schools), white some is inherent in the diversity of the environment and the surrounding conditions. The problem of CPUE variations may be resolved in two ways:

1. Increasing the number of units of fishing effort (stations fished) enough to bring about a decrease in CPUE. This solution, however, only deais with random variations and is not aiways applicable for budget and time reasons.

2, Attempting to explain the fraction of CPUE variation due to environmental, weather and other factors.

The second option was adopted. We first Iooked for parameters likely to influence the catch of Brown Bullhead, Carp and Yellow Perch young—of—the—year in Massettes Marsh. Only independent parameters which could be used in other managed marshes were considered:

Depth

Water depth is the parameter most often used to explain the spatial distribution of fish. In wetlands, shallow depth may, in certain locations, be a limiting factor for fish.

Percentage of free water at the station

The proportion of water free of emergent and floating vegetation may influence the abundance of fish in several ways. Too thick a plant coverage limits access by fish. It may also, by blocking the action of wind and the penetration of light, prevent the replacement of dissolved oxygen by water mixing and the photosynthesis of submergent plants. Dense plant coverage also produces a thick layer of organic debris every year which, by decomposing, further limits dissolved oxygen. The overall effect may be the creation of stagnant bodies of water where the physical and chemical conditions are not vert' favourable to fish. Some plant coverage may, however, be essentiel to fry, serving as a refuge from predators and maintaining the population of invertebrates which form the basis of their dist.

Station accessibility

This parameter allows us to calculate the number of obstacles (particularly vegetation) around a station. These obstacles may limit the access of fish to the station and, up to a point, act on physical and chemical conditions in the same way as the previous parameter.

Percentaae of submergent plants

Submergent plants generate oxygen in the environment and are colonized by a great many small organisms eaten by fry. They may also serve directly as food for species such as Carp and form a shelter from predators. For these reasons, they may have an effect on the abundance of young—of—the—year.

Distance from main channel

The main channel is the deepest habitat in the managed marsh. The concentration of some young—of—the—year may thus depend on proximity to this channel.

Distance from the control structure and spillwav

In Spring 1989, during the spring flood, fish appear to have entered the managed marsh by two opposite points located under the high—water level: the control structure at the southwest tip of the marsh and the spillway (two close entrances) at the southeastern tip. The distribution of spawners in the marsh thus took place from these access points, so it is possible that a greater number of them spawned near these entry points. If this was the case, the concentration of fry might be higher near these points.

Fishino effort

It proved Impossible to maintain an entirely constant fishing effort with a fyke net.

The average fishing effort was 19.3 hours with a standard deviation of 2.9 hours.

It was considered that this variation in fishing effort might have had an influence on CPUE.

Cumulative fishina effort

Verdon (1979) reports that fish may become accustomed to fishing gear, and this means we had to envisage the possibility that CPUE would graduaily decline in successive fisheries.

Phases of the moon

By providing light at night or by the attraction it exercises, the moon may influence the activity of fish and consequently CPUE.

Weather factor

Cloud, wind speed and direction, temperature variations between day and night and atmospheric pressure were considered since they could influence fish activity and thus cause variations in CPUE. The values of these parameters came from

26

the Environment Canada Gatineau Airport station and the Quebec Environment Department Angers station.

For each species, the CPUE multiple regression equation based on p variables among those mentioned above was calculated.

CPUE = a + blX1 + b2X2 + + bpXp

Only significant variables were maIntalned In these regression equations, i.e.

variable that maintalned a significant effect on CPUE, when the affect of other variables is constant (partial significant correlation).

These multiple regression equations were then used to calculate q:

CPUE a + blX1 + b2X2 + + bpXp q=

(NiS) (N/S)

Application of the model

Use of the model in a different environment or in the same environnent at another time is carried out In three stages:

1. Experimental fishing with small fyke net is first conducted at n stations where CPUE and the values of p parameters used to calculate q are noted.

2. A population estimate is next calculated based on the data gathered at each station using the formula:

N = CPUE/q

3. The mean of the n values of N is then calculated.

It should be borne in mind that such a model is aimed at providing an order of magnitude rather than an exact population estimate. The accuracy of this order of magnitude MI depend on the number of stations to which the model was applied. Application of the model is also Iimited by the range of values of the parameters on which it is based. It would, for example, be risky to use the model in an environment where the parameters have values very different from those observed in Massettes Marsh, or to use it outsicle the summer period, when the parameters influencing the abundance of fish in varlous locations might be different.

2.5 Analvsis of certain aspects of the dvnamics of voung—of—theyear population

2.5.1 Survival rate of Brown Bullhead vouna—of—the—vear in the manaaed marsh

To determine the value of managed environments as a spawning site, the survival rate of Brown Bullhead young—of—the—year, from the egg stage to the end of the summer, was calculated based on estimates of populations of adults and youngs.

Unknown parameters needed for this calculation were obtained by referring to studios on that apodes in other bodies of water in Quebec.

Sex ratios

According to Harvey and Fortin (1982a and b), the sex ratio of Brown Bullhead entering the spawning area in the Rivière aux Pins near Montreal is not significantly different from the theoretical ratio of 1 male: 1 female, whatever the age and size of individuals. Rubec (1975) reports the same thing for the Brown Bullhead in the Ottawa River, in the Hawkesbury and Ottawa areas. The number of female Bullhead in Massettes Marsh was thus caiculated on the basis of adult population estimates made in August, assuming that haif of these fish were females.

Population of mature females

Harvey and Fortin (1982b) calculated that few Brown Bullhead females are mature before reaching 170 mm. Their research indlcates that for size classes from 170 to 220 mm the percentage of females capable of spawning is 25, 45, 60, 87, 92 and 100%. From 220 mm, all females can spawn. These proportions were used to calculate the number of Brown Bullhead females which spawned in 1989 in

Massettes Marsh.

Relative fertillty of females and number of eaas released in Massettes Marsh in 1989

Harvey and Fortin (1982b) found a linear relation between the weight of female Bullhead 227 to 347 mm long and the number of eggs in their ovaries: Fertility = 747.30 + 13.18 Weight (g). This relation yields relative fertilities in the same order of magnitude as those obtained in other bodies of water in Quebec, such as the Rivière du Nord (Phaneuf 1974) and the Ottawa River (Rubec 1975).

To use this relation, the average weight of the Brown Bullhead females of Massettes Marsh was calculated by 10-mm length class, using a semple of 722 adults. Although the sex of Individuels was not determined during this operation, Harvey and Fortin (1982a) maintain that the weight of male and female Bullhead of a given length is not significantly different. However, 7.5% was added to the average weight calculated, since the Fertility/Weight ratio applies to gravld individuals whose full gonads would account for this additional weight (Harvey and Fortin 1982b).

Using the number of mature females by length class, their average weight and the Fertility/Weight ratio, the fertility of the Brown Bullhead of Massettes Marsh and the total number of eggs released in this environment in 1989 were estimated.

Survival rate of vouna Brown Bullhead in Massettes Marsh

The survival rate of young Brown Bullhead of the year, from the egg stage to the end of the summer, was obtained using the ratio of the estimated population of young Bullhead of the year to the number of eggs reieased.

2.5.2 Growth of young-of--the—year in the two marches

A general pattern of growth in length of young—of—the—year was determined based on samples of total length measurements taken during the three sampling campaigns. The samples varied from 10 to 500 individuels in the naturel marsh, depending on species and period.

The mean, standard deviation and limit values of lengths observed were first calculated for different dates in June, July, August, October and November.

Growth curves were then constructed and the growth of fry compared between the managed marsh, the naturel marsh and other bodies of water in North America.

3. RESULTS AND DISCUSSION

3.1 Characterization of environments

3.1.1 Habitat cateaories

In the managed marsh, three types of habitats ware identified:

1, A main channel with an area of one hectare follows the dyke for a distance of 1.8 kilometres. This channel, with an average width of 5.5 metres, was dug in the clay. It forms a highly uniform habitat without vegetation.

2. Secondary channels flow from the main channel towards the interior of the marsh. These channels, which cover an area of approximately 2,800 square metres, are more heterogeneous. They vary in width from 1.5 to 5 metres.

Some portions of these channels are covered with vegetation, white other have none.

3. Most of the surface of the marsh is a shallow habitat where vegetation is abundant and diversified.

In the natural marsh, habitats are divided into two main classes: areas under water all year (except during freeze-up) and areas dewatered during the summer.

The first group includes stations 1-2,1-4, 1-6,1-8,1-10, I1-1, III-2, 111-2A,111-2B and

111-3.

3.1.2 Plant coveraae

Manaaed marsh

The characterlstics of plant coverage in the shallow part of Massettes Marsh in June and July 1989 are summarized in Appendix 1. Since this plant coverage has already been partly described in a previous study (Pépin et al. 1990), only the main points will be dlscussed here.

Vegetation covers an average of 49.4% of the surface of the sites vislted. This estimate is close to DU standards, which are aimed at maintaining 50% plant coverage in managed areas. The percentage of coverage does, however, vary from 3 to 95% in different areas. Over half (54%) of the plant coverage is emergent vegetation, while floating plants maks up the remaining 46%.

On average, 27.7% of the bottom area is covered by submergent vegetation, although percentage coverages as extreme as 0% and 100% were also observed,

Most of the emergent, floating and submergent strata are made up of twelve, seven and nine species of macrophytes respectively.

Broad—fruited Bur—Reed (Sparaanium eurvcarpum), Buttonbush (Cephalanthus occidentalis) and Narrow—leaved Cattail (Tvpha anaustifolia) are the plant species that dominate the emerged stratum in most areas. These plants were reported in 66%, 53% and 49% of stations, where they represented up ta 40%, 63% and 75%

of plant coverage.

Frogbit (Flvdrocharis morsus—ranae) is the most abundant species in the floating stratum. It was found at all stations, where it covered up to 55% of the surface of sites. Filarnentous algae, often associated with Frogbit, ranked second in this stratum. The percentage occurrence at the stations sampled was 61%. In certain places, they represented up to 37% of the plant coverage.

The main species found in the submergent stratum were American Eelgrass (Vallisneria americana), Whitish Water—Milfoil (MyrioahvIlum exalbescens) and Water Stargrass Heteranthera dubia). They were identified in 51%, 51% and 43%

of stations respectively, where they represented up to 40%, 60% and 90% of the plant coverage.

Natural marsh — June

Appendix 2 presents the characteristics of plant coverage in Daragon Bay in June.

In June, vegetation covered an average of 43.2% of the surface of ail stations visited, or 58.6% of the surface of stations in dewatered areas and 34.3% in permanently flooded stations. The emergent stratum is the dominant stratum in exposed areas, accounting for an average of 50.5% of coverage. In flooded areas, it is the submergent stratum that has the greatest average coverage at 50%. The floating stratum is also greater in flooded areas, representing 17.9% of coverage on average compared to 8.3% in dewatered stations.

1. Permanently flooded areas

Bur—reeds (Saaraanium anaustifolium, Saaraanium eurvcaroum and Saaraanium spp.) and Pickerel—weed (Pontederia cordata) dominated the emergent stratum from permanently flooded areas. They were found in 86% and 57% of the stations where they were dominant or co—dominant. Buttonbush was present at only one station where it covered 15% of the surface sampled. Narrow—Ieaved Cattail was also quite poorly represented (two stations at 5% or less).

At certain stations, young shoots of emergent and floating vegetation were included in coverage of the floating and submergent strata in June. Since this error could not be corrected alter the tact, only the percentage coverage of species typical of each of the strata have been discussed.

The species found in the floating stratum were not particularly dominant. Water—

Illies (Nymphes odorats or tuberosa) were found in 86% of stations where they accounted for more than 10% of coverage at only two stations. A species of Pondweed (Potamooeton spp.) occupled less than 3% of the surface in 42% of stations and Frogbit represented less than 3% of coverage in 29% of stations.

The main species found in the submergent stratum were Water Stargrass, American Eelgrass and Common Bladderwort (Utricularia vuloaris). They were identified in 86%, 71% and 71% of stations respectively, where they accounted for up to 25%, 50% and 15% of plant coverage.

2. Exposed areas

In areas free of water, the diversity of the emergent stratum was much greater.

Each station was dominated by a different species: Broad—fruited Bur—reed, Reed Canary Grass (Phalaris arundinacea), one species of Spike—rush (Eleocharis spp.) and Sedges (Carex spp.). These species occupied 39%, 17%, 25% and 20%

respectively of the stations where they dominated. Bur—reeds were present in the three other stations and occupied up to 25% of coverage. Other species occupying 10% or Iess of this stratum in 25% to 75% of stations were Cat—tall, Arrowhead (Sanittaris spp.), Purple Loosestrife (Lythrurn Salicaria), Sensitive Fem (Onoclea sensibilis), Pickerel—weed and Great Bulrush (Scirpus validus).

Frogbit was the main species found in the floating stratum. It was present at 75%

of stations where it represented 1% or 24% of coverage. A species of Spike—rush, Common Water—lily, and Common Duckweed (Lemna minor) occupied Iess than 2% of coverage in 25% of stations.

There was no submergent stratum in one out of four stations. Common Coontail (Ceratophvllum demersum) occupied 20% of coverage in one of the stations and 2% in another. Needle Spike—rush (Eleocharis acicularis) and filamentous algae made up the rest of the stratum, each with 4% or Iess of coverage.

Natural marsh August

The characteristics of plant coverage for August are summarized in Appendix 4.

In August, vegetation covered 74.9% on average of ail stations visited. The marsh thus closed considerably between mid—June and mid—August. This observation is particularly valid for uncovered areas where the average percentage coverage rose to 98.3%. The floating stratum then formed only 1.0% of average coverage and the submergent stratum 0.8%. In fact, these stations were all under less than two centimetres of water during this period (Table 10). Areas stiil under water had an average of 64.4% of their surface covered with vegetation. The submergent stratum was the greatest, with average coverage of 77.8% compared to the floating stratum which occupied 20.6% of the surface and the emergent stratum which covered 43.9%.

1. Permanently flooded areas

Bur—reed and Pickerel—weed were still present in 89% and 56% respectively of stations where they occupied up to 30% and 10% of the surface sampled. Other species, however, became more important in August. This was the case, for example, for Arrowhead (Sagittaria latifolia and Sacittaria rigida) which covered 4% to 34% of the surface in 78% of stations. Flowering Rush (Butomus umbellatus) occupied 5% to 30% of the space sampled in 33% of stations and Wild Rice (Zizanie palustris) covered up to 58% of the surface in 22% of stations.

Cattail and Buttonbush were observed at only one station each and accounted for only 1% and 2% of coverage.

The floating stratum was dominated by Water—lilies. They were observed in all stations and covered up to 41% of the surface. Frogbit was present in 78% of stations, although coverage never exceeded 6%. Common Duckweed, two species of Pondweed (Potamogeton spirilus and Potamogeton spp.), Variegated Pond—lily (Nuphar variegatum) and Scarlet Knotweed (Polvaonum coccineum) were observed at less than 25% of stations with coverage of less than 4%.

The three main species found in the submergent stratum were Common Coontail, Whitish Water—Milfoll and Needle Spikerush. They were observed in 78%, 67%

and 44% of stations respectively, where they accounted for up to 50%, 66% and 75% of plant coverage. Water Stargrass and Common Bladderwort were aiways present but only in 33% and 44% of stations respectively. Two new specles with moderate to light coverage were noted during this period, Canada Waterweed (Elodea canadensis), which was present in 66% of stations where it covered 2%

to 20% of the surface, and Water Marigold (Bidens. Beckii), present at only one station and accounting for 3% of coverage of the stratum.

The differences observed between June and August may be due to three main factors. First, Identification of new plant specles in August may be the result of normal changes in plant coverage during the strongest growing season, in July.

As well, changes in the proportions of different species at a given station may also be due to different growth rates of species during the summer or to slight changes in the boundaries of vegetation quadrants from one period to the next. Moreover, the possibility of error in identifying certain plants not completely developed in June must be considered, which might expiain the absence of American Eelgrass in August whereas it was abundant in June. What was considered Eelgrass in June may have been young shoots of Bur—reed that were completely upright in Aug ust.

2. Drying areas

In dewatered areas, the emergent stratum was dominated by Bulrushes (Scirpes spp.) and Sedges (Carex spp.) at two of the four stations. These specles occupied up to 35% and 55% of the surface respectively. Flowering Rush (40%) co—dominated with Bur—reeds (32%) at a third station and one specles of Spike—

rush (Eleocharis spp.) covered 60% of the fourth. Broad—leaved Arrowhead was present at all stations with coverage of 15% to 22%. The remainder of the stratum was occupied by the same species as in June (Canai', Purple Loosestrife, Sensitive Fern) in the same proportions (Iess than 12%) and by Buttonbush which covered 5% of the surface of one station.

There was almost no floating stratum, being represented by Frogbit with less than 4% coverage at two stations. The submergent stratum was present at only one station where Coontail was the only species present (3% of coverage).

3.1.3 Phvsical qnd chemical characteristics

Manaqed marsh

The physical and chemical characteristics observed in June, August and October in the channels of Massettes Marsh are summarized in tables 2 to 4. Tables 5 to 7 present the measurements taken in the shallow part of this marsh.

1. Depth

The depths encountered in Massettes Marsh in 1989 ranged from less than fine centimetres to a little over two metres.