Community Fisheries Assessment Program

 

 

 

 

 2006

 

 

 

 

 

 

 

 

 

 


Table of Contents

 

Introduction   3

Methodology   4

Results   5

Discussion   5

Recommendations   6

Acknowledgements   7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.1       Introduction

 

Lake trout are an important part of Ontario’s biodiversity due to the unique character of the species and the unique genetic strains of inland stocks. Despite this, there has been a general decline in both the quality of the fishery and in lake trout habitat in many lakes for a variety of reasons.  Although we have lost some native Ontario populations, the Bancroft area supports some of the southernmost inland native lake trout lakes in Canada. 

 

Historically, lake trout have been reared in hatcheries and widespread stocking of non-native hatchery-reared strains has occurred.  Stocking objectives vary, but generally provide artificial, short-term fishing opportunities that are dependent on continual stocking.  Recent science and assessments have shown that stocking over existing naturally reproducing populations may be detrimental for several reasons. Unique genetic diversity is irreversibly lost when native fish populations are reduced or eliminated, which impedes rehabilitation efforts and increases ecological instability. 

 

Science has shown that isolated populations of the same species possess certain characteristics which make them better adapted for survival in that area. Therefore, native stocks are best suited for the specific habitat in which they have adapted and currently live.  A unique genetic strain has been identified in several lakes in the Bancroft-Mazinaw area.  Further assessments, collections and genetic analyses are required to determine the extent of the distribution of the special locally adapted strain(s) of lake trout.  The objectives of lake trout management in the Bancroft/Mazinaw Area will be aimed at ensuring these unique natural lake trout populations are sustained. 

 

The Lake Trout Management Strategy for the Bancroft-Mazinaw Area has a community based component and includes a community hatchery and native rehabilitative stocking initiative to work towards restoring and rehabilitating native lake trout populations.  A considerable amount of assessment work is required to determine the status of lake trout lakes, including the genetic origin, and rank lakes as poor (needing rehabilitation), okay (potential for rehabilitation), or good (do not require rehabilitation and may represent a source of eggs).  This process will help us identify lakes that can be helped with rehabilitative stocking and lakes that could become donor lakes (lake trout eggs could be collected, raised and restocked into rehabilitation lakes).  Therefore, the Bancroft Area Stewardship Council and Ministry of Natural Resources Bancroft District office designed an innovative approach for gathering this scientific data that utilized the support available from the local angling and outdoor community.  This approach supports the strategic direction and current priorities of the Ministry of Natural Resources as outlined in the guiding document “Our Sustainable Future”.

 

Beginning in May of 2006, a crew consisting of MNR employees and community volunteers conducted Spring Littoral Index Netting (SLIN) and Summer Profundal Index Netting (SPIN) on 7 different lakes.  The goal of this netting was to obtain a point-in-time density estimate and to collect genetic information.  Density estimates permit the categorization of a population into three basic density ratings: low, medium, or high, and allow for a relative comparison of the state of the lake trout resource throughout the area.  These ratings will assist in identifying donor and recipient lakes within the Bancroft/Mazinaw Area. Donor lakes will provide fertilized eggs for the lake trout community hatchery, which will in turn supply fish to recipient lakes.  Genetic profiling will be completed prior to stocking to ensure stock is compatible. 

 

 

1.2             Methodology

 

Prior to the field season, a group of nine volunteers participated in a training session that included safety training and netting procedures.  Further training was done in the field to ensure a safe and productive survey. 

 

In order to maximize the sampling season, both Spring Littoral Index Netting (SLIN) and Summer Profundal Index Netting (SPIN) methodologies were used.  This allowed netting to begin in May and continue until mid September.  Table 1 compares these two protocols.

 

Table 1: SLIN vs. SPIN methodology 

 

SLIN

SPIN

Timing

After ice melt,

Prior to 13 C surface Temp

July 15 to 18 C surface temp

Net Type

91.4m long.  3 nets with either 38mm, 51mm,or 64mm mesh sizes

64m long. Constructed from 8, 8m panels (57mm, 64mm, 70mm, 76mm, 89mm, 102mm, 114mm, 127mm) in randomized order.

Set Duration

90 minutes

120 minutes

Depth

2.5m to a maximum of 60m

Three depth strata: thermocline to 20m, 20-30m, 30-40m.  Ratio of nets set in each is dependent on relative area and catch success in each strata. 

Orientation

Perpendicular to shore

Random

Oxygen

N/A

3mg/L or higher

Sample Size

Minimum 5 days, 30 net sets

Depends on lake area >10m depth

Site Selection

Shore marked off into 100m sections, and numbered sequentially.  Sites are randomly selected, assuring a minimum 500m between sites on a given day. 

Either through random grid selection or by visually ensuring even coverage. 

Fish Sampling

Fork length, round weight, sex, gonad condition, ageing structures, clips, genetic sample

Data Management

FISHNET 3

SPIN Support Spreadsheet and FISHNET 3

           

1.3             Results

 

Netting was completed over a 31 day period.  Eight volunteers participated over a twelve day period for a total of 97 volunteer hours. 

 

A total of 7 lakes were completed during the 2006 netting season, 2 lakes using the SLIN methodology, and 5 using the SPIN.  Results are summarized below in Table 2.  Raw data is attached in Appendix 1.  There are two columns for Catch per Unit Effort (CUE).  The first is a measure of the total number of fish (lake trout) caught per hour of netting.  The second column is a SPIN CUE which represents fish over 300mm caught per net set (2hours).  The two columns are presented so that the smaller fish can be represented for the SPIN lakes, while still allowing conclusions to be drawn based on SPIN methodology which does not include lake trout under 300mm.  The density estimate is based on the SPIN CUE, the area of suitable habitat and whether or not the population is small or large bodied.  RSE is the residual standard error (estimate of accuracy) with a target of 0.15.  The sample size is the total number of lake trout caught.  The % Natural column is the percentage of the total catch that was unclipped (assumed to be naturally reproduced and not hatchery strain).  The Average Fork Length is the mean length of all lake trout caught.   

 

            Table 2:  Summary of results

 

Lake

Method

Total Catch

CUE

SPIN

CUE

Density (trout/ha suitable habitat)

RSE

(target is

0.15)

%Natural

Average

Fork Length

(mm)

*Body

Size

Genetic

Strain

Paudash

SLIN

9

0.26

 

 

 

78%

451

Large

No Results

Shabomeka

SLIN

72

1.62

 

 

 

11%

324

Large

No Results

**Faraday

SPIN

10

0.36

0.69

3.2

0.22

100%

457

Large

No Results

**Papineau

SPIN

13

0.43

0.42

2.1

0.29

100%

323

Large?

No Results

Weslemkoon

SPIN

40

0.53

0.76

9.3

0.25

98%

310

Small

BANCROFT

Ashby

SPIN

16

0.33

0.51

5.8

0.34

100%

343

Small

BANCROFT

Lobster

SPIN

25

0.52

1.16

5.1

0.37

68%

404

Large?

No Results

L’Amable

SPIN

6

0.13

0.24

1.7

0.53

50%

522

Small?

BANCROFT

Lake St. Peter

SPIN

6

0.1

0.15

0.5

0.73

83%

433

Small?

No Results

*See discussion section for relevance of body size and question marks around body sizes

**Faraday and Papineau Lakes were assessed in 2005 using the SPIN protocol.  They were included here as they are the only other lakes in Bancroft area assessed under this protocol and are important for comparison purposes.  Numbers were calculated by entering data in the SPIN support spreadsheet version 8.0 to be consistent with the 2006 SPIN assessments.

 

           

1.4             Discussion

 

In order to assess biological criteria of each lake, a representative sample of lake trout must be attained.  A sample of 30 lake trout per lake would be considered sufficient to allow interpretations of biological indicators such as length, weight and age distributions of the population and further analysis of lengths or weights at specific ages.  Due to the low catches in the SPIN assessments, such analysis was not completed on these lakes.  However, the SPIN results will still be used in order to determine the relative status of lake trout populations in area lakes.

 

A large biological sample is not needed to calculate relative lake trout population density, lakes sampled with the SPIN protocol can be categorized into low, moderate or high.  However, the accuracy of the density estimate (measured by the RSE) is greatly improved with a larger sample size.  The density categories will assist in identifying, but may not ultimately determine, donor and recipient lakes within the Bancroft District.  Guidelines have yet to be developed within the District as to how to categorize lakes based on relative population density and will be provided in the district’s rehabilitation plan for lake trout.  As such, general statements will be made about each lake and a recommendation will be provided as to the status of each lake in this report. 

 

Due to the bias of the SPIN gear towards large bodied populations, there are different interpretations of results depending on whether the lake trout population is large or small bodied.  Based on a number of SPIN assessments throughout the province in unexploited lakes (no fishing pressure) with very simple fish communities, a CUE of around 2 fish per net is attainable in small bodied populations and up to 4 fish/net in large bodied populations (S. Sandstrom, pers comm., 2006).  However, in lakes with high fishing pressure and complex fish communities such as the majority within Bancroft District, expectations of catches are substantially lower.  In exploited populations, the general rule of thumb is a SPIN CUE (#fish / net) greater than 0.5 is average to fairly good for small bodied populations and a SPIN CUE of 1 or greater is average to fairly good for large bodied populations.  As our sample size of lakes assessed with the SPIN methodology increases, we will have a better understanding of relative comparisons amongst lakes.

 

 

 

 

 

 

 

 


Figure XX.  General categorization of exploited lake trout populations based on

Summer Profundal Index Netting Catch per Unit Effort (Sandstrom 2006 pers comm.).

 

 

Ashby and Weslemkoon Lakes can be determined to have a relatively good population of small bodied lake trout (SPIN CUE of 0.51 and 0.76 respectively), and should be explored as donor lakes for the lake trout community hatchery.  Spawning locations are known for Ashby and Weslemkoon Lakes, and both contain the unique Bancroft strain of Lake Trout.  The density estimates for both lakes are 5.8 and 9.3 fish per hectare of suitable habitat; although the RSE is greater than the 0.15 target, the estimate for Weslemkoon Lake is the most accurate of all density estimates calculated due to the highest sample size.  Out of all lakes sampled thus far, Weslemkoon clearly had the highest relative abundance.  Interestingly, Weslemkoon does have a rather complex fish community, including rock bass, largemouth and smallmouth bass, yellow perch and northern pike.  Ashby Lake had the second highest relative abundance and the fish community is slightly less complex than Weslemkoon, with smallmouth and yellow perch being the other main predators.  Ashby Lake was also the only lake with 100% native fish (unclipped), while Weslemkoon had 98%.  Supplemental stocking with hatchery strain lake trout ceased in 1995 in both of these lakes and the native population has since recovered and doing well.    

 

While results for Lobster Lake indicate a good SPIN CUE (1.16) for large bodied populations, netting in this lake continued past the 18ºC surface temperature cut-off for the protocol.  Prior to the temperature drop, no fish were caught in any of the nets.  Following the temperature drop (to 16ºC), trout were caught in a high percentage of shallow net sets (from thermocline to 10 meters maximum).  Also, approximately 30 % of lake trout captured were hatchery fish.  When the hatchery (clipped) fish are removed from the calculations, the SPIN CUE for the natural population is 0.8, which for a large bodied population (as the lake was classified in 1995 South Central Region Lake Trout Strategy) is below average.  To further complicate this matter, the average length of the unclipped fish was 368mm, which may indicate the population is in fact small bodied, in which case the SPIN CUE of 0.8 would be considered very good –better than Weslemkoon.  However, it is suspected based on body size and behaviour that these fish may be of hatchery origin (even the unclipped fish may have been produced by hatchery stock in the lake).  Genetic testing will be required on this lake in order to determine the origin of the fish and further assessment work (including locating and documentation of spawning sites and additional population assessment following the protocol) may be necessary to determine the status of this population.  The fish community in Lobster Lake is relatively simple, with yellow perch being the other main predator.  Supplemental stocking of lake trout stopped in 1995 as part of the SCR Lake Trout Stragegy. 

 

L’Amable and Lake St. Peter can be classified as poor, and should be considered potential recipient lakes.  L’Amable Lake genetics are thought to be compatible with both Ashby and Weslemkoon, although this still needs to be confirmed.  Only 50% of the fish (3 in total) were unclipped in the 2006 assessment.  Lake St. Peter genetics have yet to be determined, although 83% of the fish in the 2006 assessment were unclipped.  Both of these lakes had the lowest SPIN CUE as well as the highest RSE in the density estimates, indicating the populations are relatively low.  Both L’Amable and Lake St Peter were classified as small bodied populations in the 1994 trout strategy.  In both assessments conducted this summer, the mean length of the catch indicates the lakes may in fact be large bodied, in which case the SPIN CUEs are far below the moderate/average CUE of 1 fish/net.  Other potential explanations for the large mean length of the fish captured include a severe recruitment problem, in which there are very few smaller fish in the population.  Either way, these 2 lakes were the poorest of those assessed this summer, and are definitely potential rehabilitation candidates.  L’Amable Lake has a relatively complex fish community, including white sucker, rock bass, pumpkinseed, smallmouth bass and northern pike.  Lake St Peter is similar with a species composition of white sucker, smallmouth bass, and rock bass.  Walleye are also being reportedly caught in both lakes as well.  Both lakes had received supplemental stocking with the Great Lakes hatchery strains until the implementation of the SCR Lake Trout Strategy.

 

The remaining two lakes, Paudash and Shabomeka, were assessed using the SLIN protocol and are therefore not comparable to those assessed with the SPIN protocol.  A CUE of 0.26 was obtained on Paudash Lake, with 78% of the fish assumed to be native (unclipped).  This is considered to be a relatively poor SLIN result, but is at the high end of this range.  Paudash Lake is unlikely to represent a high priority lake for rehabilitation in the district, as there are a number of lakes that are in need of a greater rehabilitation effort.  While Shabomeka had a CUE of 1.62, only 11% of the catch was unclipped fish.  Therefore it is unlikely that this lake has a self sustaining natural population.  It is currently classified as put-grow-and take and is being stocked annually with hatchery reared fish.  Genetic results will indicate the strain of fish that should be utilized in this lake to avoid further contaminating the natural population.  It would be preferable to stock this lake with a native strain as opposed to hatchery strain in the hopes that they will reproduce on their own and become a self-sustaining population, as there is sufficient suitable habitat in this lake to be rehabilitated with a local strain. 

 

The SPIN assessments completed in 2005 include Faraday and Papineau Lakes, which would fall in the midway point between poor to moderate category for large bodied populations.  The mean length of lake trout caught in Papineau may indicate a small bodied population, although this is unlikely since there is abundant lake herring in the lake; the population was classified as large bodied in 2004.  The smaller mean length of the catch in 2005 should be looked at as it is not consistent with a large bodied population.  As with the assessments in 2006, the sample sizes were too low to complete any biological indicator analysis and genetic results are still pending.  Based strictly on the 2005 SPIN CUE and comparison of relative abundance with the lakes sampled thus far, Papineau Lake could be considered a potential rehabilitation lake, while Faraday falls further towards the moderate abundance category.    

 

           

1.5       Recommendations

 

Bancroft and Mazinaw Areas support 59 native lake trout lakes, 23 PGT lake trout lakes, and 7 rehabilitation lake trout lakes, for a total of 89 lakes.  In addition, there are 16 lakes not currently being managed as natural lake trout lakes but having reports of remnant native lake trout existing in them.  A total of 44 lake trout lakes have been identified as needing assessments for a variety of reasons, as well as the additional 16 unknown status lakes.  Of these, 7 were completed during the 2006 season leaving 53 lakes in need of assessment.  To ensure continuity of results the Provincial lake trout assessment netting technique (SPIN) should be used.  SLIN netting might be considered on lakes where historical netting was done using this method, in order to be comparable and observe trends.  Netting priority should be given to lakes considered to have good lake trout habitat in order to maximize the value of rehabilitative stocking.  If netting were to commence July 15, 2007 and run until water temperatures permit, 8 to 10 lakes could be completed with 1 field crew.  This would translate to a 5 to 6 year period to complete all identified lakes using the SPIN protocol.    

 

A standardized method of identifying donor and recipient lakes based on population density estimations should also be developed for the Bancroft District.  The criteria recommended included ranking CUEs as low (0-0.5), moderate (0.5-1.0) and very high (>1.0) for small bodied and low (0-<1), moderate (1-<2) and very high (>2) for large bodied populations, although additional factors need to be considered before rehabilitation could occur.  An unbiased system of prioritizing lakes for rehabilitation should include the relative CUE ranking versus the carrying capacity of the lake, available lake trout habitat, fish community complexity and forage base, social pressure, and community interest and involvement in long-term monitoring of rehabilitative efforts.  This would ensure a consistent approach that would maximize egg collection capabilities and ensure the best use of hatchery fish.  A lake trout strategy and rehabilitation plan is currently being developed for the Bancroft Area and will include such information.

 

 

1.6             Acknowledgements

 

This project could not have been completed without the help of our volunteers:

Jim Brockley

Denis Brown

Terry Campbell

Dennis Lefeuvre

Stan Loney

Durl Lott

Eldon Lott

Gil Luckasavitch

 

 

Special thanks is extended to the following partners:

 

Ontario Federation of Anglers and Hunters – Main Office, Zones E and F

Community Futures Development Corporation of North & Central Hastings and South Algonquin

Bancroft / North Hastings Fish Hatchery Steering Committee