The Anishinabek/Ontario Fisheries Resource Centre collaborated with the First Nation communities along the North Channel of Lake Huron – Aundeck-Omni-Kaning, Mississauga, Sagamok Anishnawbek, Serpent River and Wikwemikong Unceded – on a 5-year lake whitefish (Coregonus clupeaformis) index netting project. The impetus for this undertaking was concern that adequate information was not available for the derivation of the commercial catch quotas by the Ontario Ministry of Natural Resources. Traditional First Nation fishing waters were sampled from 2000 to 2004 using the Ontario Ministry of Natural Resources index netting methodology. A total of 2,760 lake whitefish were caught in 468 net sets, representing up to 17 year classes. The catch-per-unit-effort, as well as the number of year classes represented in the catch, was greater in Aundeck-Omni-Kaning than in the other four areas in the North Channel. The size and age at which 50% of lake whitefish are mature, ranged from 350 mm to 520 mm and 3 to 5 years, respectively. The data gathered from this study augmented the Ontario Ministry of Natural Resources biological catch data and was used in their statistical catch-at-age models for the derivation of lake whitefish commercial catch quotas in the North Channel.
Commercial fisheries, within the Canadian waters of Lake Huron, have been managed by the province of Ontario since 1899. The Ontario Ministry of Natural Resources (OMNR), Upper Great Lakes Management Unit – Lake Huron (LHMU) regulates recreational and commercial fisheries on Lake Huron determining total allowable catches and quotas on a management-area basis. Currently, commercial lake whitefish (Coregonus clupeaformis) quotas in the North Channel are determined using the commercial harvest and effort records, as well as biological information from commercial catch sampling (L. Mohr, OMNR, LHMU, Ontario, Canada, pers. comm.). Assessment tools, such as fishery independent index netting, which provide relative abundance and biological characteristics of targeted fish populations, have not been available for use in deriving the commercial quotas.
First Nation communities along the North Channel – Aundeck-Omni-Kaning (AOK), Mississauga, Sagamok, Serpent River and Wikwemikong Unceded – are actively involved or have an interest in commercial fishing, targeting mainly lake whitefish. These communities have a strong interest in the proper management of lake whitefish populations and they approached the Anishinabek/Ontario Fisheries Resource Centre (A/OFRC) to conduct a lake whitefish index netting assessment project. The A/OFRC and the above noted First Nation communities collaborated on a three-year (2002 to 2004) lake whitefish index netting project in their traditionally fished waters of the North Channel (Figure 1). This was in addition to two initial experimental index netting projects conducted in 2000 and 2001 (Gillies, 2004).
This paper summarizes relative abundance in addition to some of the biological characteristics of lake whitefish in the North Channel of Lake Huron. It also identifies existing knowledge deficits and the role of fisheries independent data in the determination of commercial catch quotas.
An index netting protocol, developed by the LHMU for use in the main basin of Lake Huron and in Georgian Bay (Cotrill, 2003), was applied to this study. Traditional First Nation fishing areas within the North Channel were identified by participating communities and index netting sites were then randomly selected within each area.
Sampling was conducted over two seasonal strata: pre-thermal lake stratification (July to mid August) and post-thermal lake stratification (mid-August to September). Water depth was categorized in two strata: 6 m to 35 m and 35 m to 60 m. Fish were captured with monofilament gillnets – 375 m long by 2 m deep – comprised of 38 mm, 51 mm, 64 mm, 76 mm, 89 mm, 102 mm, 114 mm, and 127 mm mesh panels. All panels were 50 m in length, with the exception of the 38 mm mesh panel, which was 25 m in length. Two net gangs were set overnight, fishing approximately 24 hours within each of the randomly selected grid squares. Lake whitefish were sampled for total length (mm), fork length (mm), weight (g), sex, maturity, gonad condition, lamprey wounds/scars, fin clips, and aging structures (i.e. scales and otoliths).
Mean catch-per-unit-effort (CPUE) is presented as the average number of lake whitefish caught in all net sets. The mean fork length at age 2 was used to assess growth patterns, since changes in growth are more easily detected in young, immature individuals, which tend to exhibit rapid somatic growth. One-way ANOVA was used to test for differences between areas for mean fork lengths at age 2. The ages at which 50% of the population would be mature were estimated from logistic regression equations (Maturity = exp(a+Age*b)/ 1+exp(a+Age*b)). In all cases, the accepted level of significance was p < 0.05. Systat (version 10.2, 2002, SYSTAT Software Inc.) was used to perform statistical analyses.
A total of 468 net sets were completed over the 5-year period catching a total of 2,760 lake whitefish. CPUE varied between years and areas; however, CPUE, as well as the number of year classes represented in the catch, was greater in AOK than in the other four areas (Table 1). For comparative purposes, netting effort and CPUE for the North Channel plus four other sample areas within Lake Huron, are summarized in Table 2 for 2001 to 2003. The information for the latter four areas was obtained from LHMU studies which were conducted during similar time periods and using the same methodology (Cottrill 2001, 2002, 2003). The netting effort was much greater in the North Channel in comparison to the other four sample areas. CPUE in the North Channel was similar to that for Central Lake Huron and the Clapperton Island area, but considerably lower than reported for Southern Georgian Bay and South Lake Huron.
The mean size of 2-year old lake whitefish, for each of the five areas over the 5-year period, is illustrated in Figure 2. Two-year old fish captured in Mississauga were significantly larger (ANOVA, F(1,53) = 4.65, p = 0.03) than fish from Wikwemikong in 2001, but not in 2000 (ANOVA, F(1,58) = 1.24, p = 0.27) or 2002 (ANOVA, F(2,105) = 0.61, p = 0.54). The significant size difference observed in 2001 can be attributed to 10 fish from Mississauga, all greater than 300 mm in length. A similar relationship existed for areas sampled in 2003 and 2004, whereby age 2 fish captured in Serpent River were significantly larger than fish captured in Sagamok and Aundeck-Omni-Kaning in 2003 (ANOVA, F(2,50) = 14.0, p < 0.001), but not in 2004 (ANOVA, F(2,65) = 0.74, p = 0.48). Small sample sizes, in several of the areas, may account for these results. There was a significant decline in the mean fork length at age 2 over the 5-year period, when areas were pooled (ANOVA, F(4, 670) = 103, p = 0.00).
The age at which 50% of lake whitefish are mature, ranged from 3 years for lake whitefish sampled in Sagamok in 2002, to 5 years for fish sampled from the waters of Wikwemikong in 2000. The size at 50% maturity, ranged from 350 mm to 520 mm, for the corresponding years and areas.
An effective commercial fisheries management program requires an independent source of data, which is not solely provided by commercial catch data. Fishery independent studies, such as index fishing projects, follow a standardized procedure, remain constant from year to year, and provide information such as relative abundance and year class strength for fish that have not yet been recruited into the fishery (Maunder, 2001; Mohr et al., 2003). Assessment programs of this nature are, however, costly for any one agency, particularly in a water body the size of Lake Huron – North Channel OMNR management area alone is 315, 561 ha in size (Gile and Talyor, 2003). In times of government financial constraints, sampling effort is often curtailed or confined to specific locations. The A/OFRC was able to fulfill the lake whitefish data gap for the North Channel of Lake Huron with this five year index fishing study.
The A/OFRC index fishing data were incorporated into the LHMU statistical catch-at-age models used in the derivation of commercial catch quotas. These data have been used by the LHMU to calculate pre-recruitment indices and augment the biological catch data for southern Georgian Bay (Christian Island), northern Georgian Bay, as well as the North Channel of Lake Huron (A. Cottrill, Assessment Biologist, OMNR, LHMU, Owen Sound, Ontario, Canada, pers. comm.). Other model input parameters, compiled from these data, include size and maturity-at-age, lamprey wound evidence, percent of females in the population, and estimates of growth – which in turn are used to estimate an initial natural mortality rate (Ebener et al., 2003; Mohr et al., 2003). Although the lake whitefish index study provided useful and essential information, there is still a knowledge gap regarding lake whitefish genetics and movements. Before assumptions can be made as to whether the fish in the North Channel are a distinct population, further studies of this nature are required.
Knowledge of population distribution is vital for the purposes of establishing defensible quotas for a commercial fishery (Crawford et al., 2001). In southern Georgian Bay, lake whitefish were known to undertake migrations at certain times of the year and at specific times in their life cycle resulting in a greater mixing of populations (Cucin and Regier, 1965). A mark recapture study at South Bay suggested a lake whitefish migration route extending from southeastern Manitoulin Island, southward along the northeastern shore of the main basin, and northeast toward northern Georgian Bay (Budd, 1957). Casselman et al. (1982), however, suggest that lake whitefish movements may not be as extensive and could be restricted to areas of similar depth and/or thermal regimes. Since the distribution and migration areas of lake whitefish in the North Channel of Lake Huron are not well understood, comparisons between years, areas within the North Channel, and lake basins, must be made with the understanding that population dynamics are unknown.
Understanding the spatial distribution of fish and the allocation of fishing effort is also important when interpreting CPUE (Harley et al., 2001; Hilborn and Walters, 1992). The higher CPUE values observed in 2003 and 2004 for both Sagamok and Aundeck-Omni-Kaning, are most likely related to the geographic focus of the index netting project. The significant size differences in age 2 fish, between the various index netting areas, may be a factor of smaller sample sizes or the geographic location for a particular sample year.
Lake wide comparisons of fish attribute data are not always feasible, especially for a large waterbody such as Lake Huron. Although the netting methods for the various studies cited in this paper were similar, there are many other factors in such a large lake which can affect lake whitefish characteristics. Fish abundance in the North Channel was consistently lower than in Southern Georgian Bay and may indicate lower productivity in this area; therefore, quotas derived for Southern Georgian Bay, and other basins of Lake Huron, may not necessarily provide an indicator of acceptable harvest rates in the North Channel. Fisheries management decisions on total allowable catches or quotas, as determined using a combination of commercial catch data and index netting data, are however, managed conservatively because of the high levels of uncertainty.
The A/OFRC was able to provide fishery independent data – in the form of five years of lake whitefish index netting data – for incorporation into the LHMU statistical catch-at-age models used in the derivation of commercial catch quotas. Although the contribution of these data help to fulfill the lake whitefish data gap for the North Channel of Lake Huron, there is still a knowledge void regarding lake whitefish genetics and movements. Further research is necessary in these areas to improve the accuracy of fisheries management decisions.
Miigwetch to the field crew members who worked in all weather conditions collecting data, and to Maureen Peltier, A/OFRC Fisheries Biologist, for leading the field project. The assistance of Lloyd Mohr, LHMU, and George Morgan and Michael Mallette, Cooperative Freshwater Ecology Unit, was greatly appreciated. Funding for this project was provided by Fed Nor, the Northern Ontario Heritage Funding Corporation, and the Ontario Ministry of Natural Resources through the Anishinabek/ Ontario Fisheries Resource Centre.