Fisheries Department

Annual Walleye Fishery Report2008

Richard Rowe, Biologist/ManagerNatural Resource Department

Nipissing First NationMarch 27, 2008

Submitted for review to:

Rebecca Burns, Ontario Ministry of Natural ResourcesEd Desson, Anishinabek/Ontario Fisheries Resource Centre

Nipissing First Nation Annual Walleye Fishery Report 2008

The purpose of this paper is threefold:

1. Report on Nipissing First Nation Commercial Walleye Harvest 2007;2. Update the status of the Lake Nipissing Walleye Resource, and,3. Develop and recommend a Nipissing First Nation Commercial Walleye Quota for

2008.

1. Nipissing First Nation Commercial Walleye Harvest 2007

Methods/ResultsThe Nipissing First Nation Fisheries Department received or compiled a total of 604 daily harvest reports (recorded in numbers of fish harvested) for the 2007 fishing season ending November 25, 2007. These reports were received from fifteen different commercial fishermen, or groups of fishermen that fish together. Some of these reports received were monthly harvest numbers compiled from daily catches recorded on the fishermen’s personal calendar. An additional two fishermen or groups of commercial fishermen did not report their catch. One other fisherman did not report their catch for part of the year, so this portion of harvest was estimated from their reported catch during this same period in 2006 (4,709 kg).

The NFN Fisheries Department measured and weighed a total of 1,079 walleye from commercial nets throughout the year (February, May, June, August, September, and October) from 9 of the 15 commercial fishing groups. This total includes 371 walleye caught in 3 ¾ inch mesh commercial nets set during the Fall Walleye Index Netting study. The average size of walleye caught was 42.4 cm total length, with an average weight of 793 grams (1.8 pounds). This average weight was applied to the reported numbers to get an estimated walleye harvest by weight.

The reported commercial walleye harvest for the 2007 was estimated to be 38,747 kg. In order to estimate total annual commercial walleye harvest, the catch of the two non-reporting fishermen also had to be estimated and the estimated non-reported harvest of 4,709 kg had to be incorporated. Mean harvest of the fifteen reporting groups of fishermen could be assigned to the 2 non-reporting groups (mean = 2,895 kg) and added to the reported total. However, it is my opinion that a more accurate representation of these harvests can be obtained by applying annual reported harvests from reporting fishermen with similar fishing frequencies and experience levels to the non-reporting groups. Using this method, the estimates for non-reporting fishermen are 3,860 kg and 2,872 kg, giving a total estimated commercial walleye harvest of 50,188 kg for 2007.

Discussion/RecommendationsCommercial walleye harvest in 2007 increased by 11,208 kg compared to 2006. Harvest exceeded the 38,000 kg harvest target set in the Nipissing First Nation Fishing Regulations pursuant to the Nipissing First Nation Fishing Laws by 32%.

Part of this increase in harvest was due to increased and improved reporting from the previous year; something that was discovered only recently. The ability of the Fisheries Department to manage harvest such that it was closer to the harvest target was greatly hindered by late reporting by registered commercial fishermen. While some of the late reporting was attributable to the inability of the Fisheries Department to collect the data in a regular, timely manner, some was due to fishermen withholding reports for fear of fishing closure if it was discovered that the set harvest target was reached.

After evaluating the success of the harvest reporting-harvest target system used in 2007, it is recommended that:

The Fisheries Department improve their efforts to collect commercial harvest data on a regular weekly basis;

Commercial fishermen that do not submit harvest reports in a timely manner are suspended from receiving their commercial fishing benefits which include free flake ice, use of a food grade cooler, letters of endorsement from the Fisheries Department etc.;

Efforts to slow down commercial walleye fishing when approaching the harvest target be improved and formalized in the Nipissing First Nation Fishing Regulations.

2. Status of the Walleye ResourceIn 2006 an extensive data review was undertaken and concluded that the walleye population of Lake Nipissing was not yet at a healthy state, and still considered ‘stressed’ based on analysis of numerous biological reference points, population trends and performance indicators (Rowe 2007). This situation remains relatively unchanged in 2007 with one additional observation: most of the observable trends through time continue to suggest stability or slight increases in the walleye population with the addition of the 2007 data.

Analysis for this report was limited to yield and abundance data, as age interpretation was not completed at the time of writing. However, the biological reference points and most of the population trends that can be examined suggest stability or even continued slight improvement toward a healthier state.

Evaluation of Harvest & YieldA) Biological Reference Point ComparisonBiological reference points typically have a high level of uncertainty; usually an order of magnitude on a logarithmic scale. This uncertainty limits comparison with observed values to a probabilistic approach, using a probability-generating tool such as the stochastic simulation model derived by Korver (2003). In an effort to decrease the level of uncertainty in the yield limit reference point to something less than an order of magnitude, the Fisheries Management Support System (FMSS) was used to simulate the Lake Nipissing walleye population using detailed information from the extensive trend through time data set. This computer simulation estimated the 95% confidence limits of MSY to be 1.49 kg/ha (upper) and 0.799 kg/ha (lower). These values were used as the 95% confidence limits in the stochastic simulations. Total walleye harvest on Lake Nipissing in 2007 can be estimated by adding the Nipissing First Nation commercial harvest, NFN spring moratorium (non-compliant) commercial harvest, and the angler harvest estimates derived from open water and winter creels conducted during 2007. Estimates of angler harvest in the French River and during the fall were factored in based on estimates from previous years. Other sources of harvest (NFN subsistence, Dokis First Nation subsistence, non-compliant angling) are unmeasured and not factored in, but are assumed to be constant from year-to-year.

Total angler harvest for 2007 was estimated to be 16,354 kg with upper and lower 95% confidence limits of 21,166 kg and 11,543 kg respectively. NFN spring moratorium harvest was estimated to be 6,250 kg with upper and lower 95% confidence limits of 15,971 kg and 2,182 kg respectively. (Appendix 1). Therefore total walleye harvest on Lake Nipissing for 2007 was 72,792 kg with upper and lower 95% confidence limits of 87,325 kg and 63,913 kg respectively. Using these values, there was a 90% probability that the 2007 walleye harvest was below the maximum sustainable harvest reference point as calculated using formulae by Lester et al. (2004), using the stochastic simulation model derived by Korver (2003), and the MSY confidence limits derived from FMSS.

Figure 1. Lake Nipissing Total Walleye Yield 2001-2007.

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This yield of 0.83 kg/ha (Figure 1) is 74% of the Maximum Sustainable Yield (1.13 kg/ha using formula by Lester et al. 2004), which slightly exceeds a management objective of maintaining harvest at or below 66% of the MSY (Rowe 2004) while the fishery is considered to be in a stressed state. Based on FWIN and harvest data from 1999-2002, the walleye population appeared to be stable to modestly improving at an estimated average yield of 0.765 kg/ha, which is equivalent to 68% of the MSY.

These observations suggest a high probability that present walleye yield is below the MSY reference point. It appears however, that yield is slightly exceeding the management objective of maintaining a harvest level at or below 2/3 MSY. This management objective was set in an effort to allow the walleye population to increase to a level considered ‘healthy’ by all measured performance indicators and reference points; after which time objectives and management approaches could be re-visited. As stated earlier, the Lake Nipissing walleye population has not yet reached a healthy state, but trends suggest continued modest improvement.

Therefore, it is recommended that:

Total walleye yield be maintained at a level equal to or lower than 0.765 kg/ha, which would allow a total annual walleye harvest of 66,800 kg (all harvesters combined). In terms of harvest, this means a reduction of 6,000 kg from the 2007 total walleye harvest level

Evaluation of AbundanceA) TrendsThe overall walleye catch per net during FWIN showed a slight but steady decrease from 1998 to 2002, then an overall increasing trend to 2007 (figure 2).

Figure 2. Arithmetic mean walleye catch during FWIN 1998-2006

Walleye catch calibrated for habitat

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When examining CUE of different size classes, the most notable observations from the current year are the dramatic increase in the 30-35 cm size class, and the slight decrease in the 40-45 cm size class. A slight increasing trend continued for the 35-40 cm, 45-50 cm and > 50 cm size classes (figure 3).

Figure 3. Trends in walleye FWIN CUE by size class.

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CUE < 30 cmCUE 30-34.9 cmCUE 35-39.9 CUE 40-44.9 CUE 45-49.9CUE > 50

The trends in abundance of larger walleye are more apparent by using biomass per net instead of numbers of fish caught (figure 4).

Figure 4. Trends in walleye biomass per net by size class during FWIN.

Biomass comparison

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Weighted Biomass 30-34.9 Weighted Biomass 35-39.9

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Overall, exploitable walleye biomass continued to increase.

Trends in FWIN Catch of Exploitable Walleye (> 30 cm) Biomass

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The observed increase in the 30-35 cm catch could be attributable to the recruitment of the exceptionally strong 2005 year class into that size class. This increase, combined with low angler harvest (which is focused on 30-40 cm size classes) are important factors related to the observed increases in these size classes, based on the significant relationship that exists between angler effort and FWIN catches in the 30-40 cm size class (Rowe 2007).

The observed decrease in the 40-45 cm size class was somewhat offset by increased catches in other adult size classes, leading to the observed overall stability in FWIN catch of adult walleye (>40 cm).

Biomass > 40 cm

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Without age data, it is unclear whether the observed decrease in the 40-45 cm size class is the result of a year class effect or a result of observed NFN harvest patterns in 2007, lack of angler compliance with slot regulations or a combination of all three.

Close to 90% of NFN commercial walleye harvest is in the 35-50 cm size classes (Rowe unpublished data), and a significant relationship exists between NFN commercial harvest and this size class (Rowe 2007). Overall trends in FWIN catch of this size class continued to increase (figure 7) .

Figure 7. Comparison of Walleye biomass by size class caught during FWIN.

Biomass comparison

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Biomass > 40 cm Weighted Biomass 30-34.9

Walleye over 40 cm have been protected by management efforts since 2004. Beginning at that time was a full-year protected slot size regulation of 40 cm to 60 cm for anglers and a moratorium on NFN gill net fishing during the spring walleye spawn. Since these regulations were implemented, there has been a continual increase in walleye greater than 40 cm observed in FWIN catches until 2007. The Nipissing First Nation gill net moratorium was unsuccessful during this same year and could at least partially account for the lack of increase in adult walleye observed in the 2007 FWIN. With the observed decrease occurring in the 40-45 cm size class, trends in angler compliance with the protected 40-60 cm slot size should also be investigated, as frustration with this regulation has been evident during roving creel surveys. Based on the available data, these possibilities can only be considered speculation at this time. As a precaution, future management should attempt to address these concerns.

B) Biological Reference Point Comparison: Exploitable Walleye BiomassA probabilistic approach similar to that taken with the yield analysis was taken to examine abundance, using exploitable walleye biomass (walleye > 30cm) caught during FWIN as the abundance indicator. Stochastic simulation suggests that there is a 62% probability that the observed exploitable biomass exceeds the exploitable biomass at MSY criterion (BMSY). In 2006, this probability was only 49%, suggesting improvement in walleye abundance toward a healthier state. A walleye population objective of having an 80% probability that observed abundance exceeds BMSY was set in 2004 (Rowe 2004). If present trends continue, this management objective may be within reach in the next few years. Therefore, harvest levels should not increase at this time, as presently they

appear to be at a level that allows slight improvement of walleye abundance toward a healthy state.

C) Biological Performance Indicatorsi) Spawning Stock Benchmark.

As mentioned in earlier reports, the sustainability of the Lake Nipissing walleye fishery has depended on the production of strong year classes to replenish its stocks on what appears to be a cyclical basis since the monitoring of yearlings began in 1979. Production of strong year classes is dependent on many known and unknown biotic and abiotic factors. Some known influences include available forage, spawning substrate, weather during and after spawn, water levels, climate, growing season etc. Another important factor in producing strong year classes is having a critical mass of adult spawning fish in the population. Therefore many management benchmarks related to the abundance of spawning-sized walleye (walleye >40 cm TL) have been used as biological performance indicators for Lake Nipissing.

Benchmark: Spawning stock abundance > 1998 FWIN Observations.Adult walleye biomass (> 40 cm total length) observed in FWIN studies from 1998 to 2002 was sufficient to produce strong year classes in 1998, 1999, 2001 and 2003. This observation suggests that the abundance of adult walleyes at that time was at a sustainable level, since the population could and was seemingly replenishing itself with regular strong year classes. The lowest observed adult walleye biomass during this period was in 1998, and is therefore used as a performance indicator.

In 2007, adult walleye biomass observed during FWIN was significantly greater than that measured in 1998 (shallow sets p = 0.01; deep sets p = 0.01). This observation suggests that adult walleye biomass observed in 2007 is at a level that is capable of producing strong year classes.

ii) Morgan – Biological Performance Indicators.Another index of Lake Nipissing walleye population health is available by comparing FWIN results against biological performance indicators developed by Morgan (pers. comm.). These performance indicators are:

FWIN Catch Per Unit Effort of Walleye Greater than 450 mm;

Number of age classes in FWIN sample;

Maximum age of walleye in FWIN catch; and

Shannon-Diversity Index of Mature Female Walleye.

These performance indicators are combined into an overall ‘Morgan Score’ as

another tool to assess walleye population health. Because age interpretation for 2007 was not available at the time of this report, only the FWIN CUE of walleye > 450 mm could be examined. Comparison against this biological performance indicator suggests a steadily improving trend:

FWIN CUE Walleye >450 mm

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iii) Lake Nipissing-Specific Performance Indicators.A ten-year continuous FWIN data set has now been established for Lake Nipissing (1998-2007). Comparison of the present-year FWIN results to the existing data set (previous 9-years in this case) can be used as another biological performance indicator. A catch at or above the 75th percentile could be considered ‘excellent’; while a catch below the 25th percentile could be considered poor and cause for concern. These comparisons combined with directional trends through time could be a useful performance indicator when evaluating the state of the Lake Nipissing walleye resource.

Figure 9. Walleye catch per net during the 2007 FWIN compared to catch in previous years.

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Figure 10. Walleye biomass (kg/net) during the 2007 FWIN compared to previous years.

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It can be observed that the only components of the 2007 FWIN catch below the median of the 10 year data set are CUEs of 35-40 cm and >50 cm walleye. However in both cases, catches have increased from the 2006 observations.

Comparisons can also be performed using size classes based on exploitation patterns. All 30 cm walleye are considered ‘exploitable’, or vulnerable to be caught. The 40 cm and above size class is considered to be composed of mature fish. The 30-40 cm size class is where almost all angler exploitation occurs, while the 35-50 cm size class

is where most of the NFN commercial exploitation occurs. Based on the 2007 FWIN results, all of the above size classes are ‘performing well’ compared to the results from the 10-year data set.

Figure 11. Walleye catches by exploitable size classes during 2007 FWIN compared to previous years.

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The above performance indicators suggest that the walleye population as measured in 2007 is performing ‘well’ relative to the nine previous years. This can be considered a positive sign that the walleye population has not become worse since FWIN measurement began. However, the above is a relative measurement suggesting relative improvement; it does not indicate nor suggest that the walleye population of Lake Nipissing is ‘healthy’, since the population has not yet been measured by FWIN in what could be considered a ‘healthy’ state.

All of the available data as compared to biological reference points, trends through time and biological performance indicators suggests that the Lake Nipissing walleye population as measured by FWIN in 2007 is improving. The data does not suggest that the walleye population is in a healthy state and therefore harvest should continue to be managed at conservative levels in an effort to continue population improvement.

3. Proposed 2008 Harvest Management SystemIn order to be recognized as sustainable managers of Lake Nipissing, Nipissing First Nation needs to use a harvest strategy that is compliant with the federally recognized ‘Precautionary Approach’ (DFO, 2006). The Precautionary Approach is a general philosophy to managing threats of serious or irreversible harm where there is scientific uncertainty. In fisheries, this approach uses a set of limit reference points to describe stock status, and harvest is adjusted based on where stock status is situated relative to these reference points (figure 12).

Figure 12. Conceptual diagram of the precautionary approach to fisheries management.

Stock status below Limit Reference Point is critical; harvest levels must be minimal to assure survival of fish population;

Stock status above Upper Stock Reference Point is Healthy, and can be harvested close to Maximum Sustainable Yield (MSY);

Stock status in cautious zone requires a reduced harvest level; well below MSY with the goal of continually improving stock status until it exceeds the Upper Stock Reference Point.

Based on all available data, it appears that the Lake Nipissing walleye population is somewhere in the ‘Cautious Zone’ and therefore needs to be managed at a level well below the Maximum Sustainable Yield.

Nipissing First Nation has completed two formal management cycles for its commercial fishery. These cycles combined with status of the fishery observations and angler harvest observations can be used to set up a sustainable harvest management system for 2008. The following considerations were used to set up the proposed harvest management system:

Until the Lake Nipissing walleye population can be considered to be in a ‘healthy state’, total walleye harvest should never exceed 2/3 of the Maximum Sustainable Yield, or a harvest of 66,800 kg;

The average annual angler harvest has been 20,458 kg since the implementation of the protected slot size during the winter angling season;

Nipissing First Nation’s moratorium on gill nets during the walleye spawn failed in 2007, and harvest during that period was significant; estimated to be 6,250 kg. This moratorium failure coincided with a decrease of walleye size 40-45 cm during FWIN of the same year;

Nipissing First Nation reached, then exceeded its harvest target of 38,000 kg, but this was not known until close to the end of the season due to late harvest reporting;

A successful Daily Catch Reporting-harvest quota system is required by fish buyers in order to purchase fish;

While the walleye population of Lake Nipissing is still considered ‘stressed’, most trends during 2007 assessment suggested stability to improvement with the observed harvest levels.

Proposed 2008 Harvest Management SystemThe term ‘quota’ needs to be used in the Nipissing First Nation Fishing Regulations and adhered to as such; since it is the cornerstone to sustainable and successful commercial fisheries management.

Walleye available for sustainable harvest by Nipissing First Nation in 2008: 46,342 kgRationale: This level represents the difference between 2/3 MSY and the average angler harvest for the past four years (66,800 kg – 20,458 kg). This harvest target is consistent with a precautionary approach to management as outlined above.

Beginning walleye quota: 41,800 kgRationale: This level represents a 10% increase over the previous year; an approach analogous to the Quota Adjustment Protocol used by the Lake Nipigon Fisheries Assessment Unit Technical Committee to manage the Lake Nipigon commercial whitefish fishery:.

The Quota Adjustment Protocol for Lake Nipigon defines the following steps to adjust quota annually:1. If stocks are stable, quotas will not be adjusted.2. If stocks are down, quotas will be decreased by 10%.3. If stocks are up and quotas are achieved (i.e. >75% of lake-wide quota harvested in the previous

year) quotas will be increased by 10%.4. If stocks are up and quotas are not achieved, quotas may be increased by 10% depending on

circumstances for quota not being achieved, to be discussed…5. Where biological data is inadequate or unavailable for any reason, then quotas will generally not

be adjusted.

Walleye Quota Potential Amendment 1 (May 11, 2008): Potential quota increase of up to 4,500 kg, depending on success of moratorium. On May 11, estimated moratorium harvest will be subtracted from 4,500 kg, and the difference will be added to the initial 41,800 kg quota. Therefore, quota could become as high as 46,300 kg.Rationale: The total Nipissing First Nation harvest must not exceed 46,342 kg regardless of the source of this harvest (excluding subsistence). In order to be considered sustainable managers, a sustainable management system with a high rate of compliance must be in place. Maintaining harvest at or below 46,342 kg is scientifically defensible,

compliant with the Federally endorsed Precautionary Approach and demonstrates a commitment to sustainability of the Lake Nipissing walleye population.

Walleye Quota Potential Amendment II (October 16, 2008): Another potential quota increase. On October 16, an angler harvest estimate for 2008 will be possible. If this harvest level is under the projected 20,458 kg, the difference can be added to the Nipissing First Nation commercial harvest quota for the remainder of the 2008 season.Rationale: Presently, the harvest management objective for the Lake Nipissing walleye population is a total annual harvest that does not exceed 2/3 the Maximum Sustainable Yield. If angler harvest is below average at the end of the angling season, then the difference is then available for commercial harvest without exceeding the overall 2/3 MSY harvest objective.

ReferencesDFO, 2006. A Harvest Strategy Compliant with the Precautionary Approach. DFO Can.

Sci. Advis. Sec. Advis. Rep. 2006/023.

Korver, Rob, 2003. Personal communication.

Lester, N.P., A.J. Dextrase, R.S. Kushneriuk, M.R. Rawson and P.A. Ryan. 2004. Light and temperature: key factors affecting walleye abundance and production.

Transactions of the American Fisheries Society 133: 588-605.

Lester N.P. In Prep. Biological reference points for walleye. OMNR unpublished.

Rowe, R. 2004. Lake Nipissing Walleye Data Review. OMNR North Bay District, 42 pp.

Rowe, R. 2007. Lake Nipissing Walleye Data Review and Harvest Level Recommendations for Nipissing First Nation. Nipissing First Nation Fisheries Department, Garden Village, Ontario. 37 pp.

Appendix 1. NFN Spring Moratorium Harvest EstimateSome netting by Nipissing First Nation members occurred during the spring when walleye were spawning, which is in contravention of Nipissing First Nation Fisheries Law Regulation 4(b) which states,“No person shall set of lift a net from April 10, 2007 to May 10, 2007 inclusive…” This law is commonly referred to as the ‘spring netting moratorium’.

It was possible to estimate the harvest during the spring netting moratorium, which has been treated separately from commercial harvest that was in compliance with Nipissing First Nation fishing seasons.

During the 31-day moratorium period, Nipissing First Nation fisheries department conducted 27 patrols at landings or on the water at times when fishermen are most likely to be encountered (early morning, late evening, night). In addition to these patrols, the fisheries department received intelligence about non-compliant fishing from residents of the south shore of Lake Nipissing, Sturgeon Falls, Garden Village and the Ministry of Natural Resources.

All of this information was organized and assembled to estimate lake-wide netting activity levels during the moratorium period similar to the methodology used to estimate angling activity during a roving angler creel survey. This data resulted in an average of 3 netting parties on the lake per night during the 31-day moratorium period (+/- 1 party, using 95% confidence limits).

Walleye harvest per netting party was estimated using 3 harvest report forms submitted during the moratorium, 13 harvest report forms submitted within 3 days of the moratorium (net sets from May 10-12), 3 harvest observations from the fisheries department, and intelligence reports received by the fisheries department and deemed to be credible. Collectively, these 23 harvest observations were used to calculate a mean catch per netting party during the moratorium. An average weight of 800 grams per fish (past average from commercial catch sampling) was used to estimate total harvest weight.

The walleye harvest observations were quite variable during the moratorium, ranging from 2 to 1,350 walleye per net set. These observations are consistent with the varying effort level of fishermen (number of net panels, location) and experience level. As a result of this variability, a geometric mean was used for harvest estimation.

The geometric mean catch per net set was 84 walleye per net, with an upper 95% confidence limit of 161 walleye per net, and a lower 95% confidence limit of 44 walleye per net. Therefore, at 3 netting parties per night for 31 nights, with a mean catch of 84 walleye each, using an average weight of 800 grams, the non-compliant walleye harvest is estimated to be 6,250 kg, but could be as high as 15,971 kg, or as low as 2,182 kg given the variability of activity and harvest per net.