Ontario muskellunge regulations and enforcement issues

In most respects muskellunge (Esox masquinongy) fishing regulations in Ontario are very similar to those for other fish species and yet the techniques of muskellunge angling and the objectives of the angler are often quite different from other targeted sport fish. This presentation will address some of the common questions and concerns raised by muskellunge anglers such as the restriction on the use of live fish as bait, muskellunge limits for Conservation Licence holders and the requirement to immediately release fish in excess of “catch-and-retain” limits and fish of prohibited size.

The presentation will also address a priority issue for OMNR enforcement. In recent years, conservation officers have found significant numbers of non-baitfish species such as yellow perch, sunfish, crayfish and bullheads in Ontario retail bait shops as well as exotic species such as goby, loach and aquarium species in angler bait buckets. The presence of non-baitfish species, in combination with the widespread and unlawful practice of “bait bucket dumping” represents a significant threat to Ontario’s aquatic biodiversity. The OMNR enforcement program is taking active steps to influence a change in angler behavior and in commercial bait industry practices

Using limited data to identify optimal bag and size limits to prevent overfishing

Bag and size limits are commonly used in recreational fisheries management, but these regulations are often treated as separate management tools. This effectively overlooks how bag and size limits can be simultaneously used to achieve multiple management outcomes (e.g., reduce exploitation, prevent overfishing, maximize angler acceptance, etc.). Our objectives were to combine data‐limited stock assessment methods with an angler catch simulation and a yield‐per‐recruit model to assess the effectiveness of bag and size limits to decrease exploitation rates and improve the spawning potential ratio (SPR ). We then applied these methods to the Kipawa Lake Walleye Sander vitreus fishery that has experienced overfishing and poor fishing quality. Using data‐limited assessment methods, the exploitation rate was estimated at 0.45 (95% CI = 0.32–0.59) and the population was overfished (mean SPR = 0.06; 95% CI = 0.02–0.13). Bag limits significantly reduced total harvest when extremely restrictive (i.e., reduced to one fish per angler from the current limit of six), but changes in bag limits alone were not sufficient to prevent overharvest because SPR remained below 0.35. Size limits could be used to prevent overharvest with narrow harvest slots (up to a 14‐cm slot range with a minimum harvestable size greater than 32 cm) or large minimum size limits (>52 cm) at the current bag limit of six. When bag limits were reduced to one or two fish per day, harvest windows could be 3–13 cm larger and minimum length limits could be 3–12 cm lower to prevent overharvest. This analysis outlines a relatively simple and effective method that can be applied using data commonly collected in annual agency surveys to predict which regulatory combinations can be used to prevent overharvest, reduce exploitation rates, and maximize angler satisfaction and acceptance of regulations. Finally, the data and model code are included in the Supplement and can be easily applied to other data limited fisheries.

Changes in the muskellunge fishery and population of Lake St. Clair after an increase in the minimum size limit

In response to high harvests and indications of stock declines in the late 1970s and early 1980s the minimum size limit for muskellunge (Esox masquinongy) for Lake St. Clair was elevated from 76 to 102 cm (30 to 40 inches) in 1987. This regulation change was implemented to protect female muskellunge through two repeat spawnings and to support a muskellunge management objective for a high quality trophy fishery based on natural reproduction. Changes in the muskellunge stock and fishery of Lake St. Clair were demonstrated by calculating length group specific indices of relative abundance. This analysis indicated that an immediate and dramatic increase had occurred in the newly protected 76 to 102 cm length group (an average annual increase of 15% with a doubling of the stock in seven years). Elevation of the minimum size limit afforded important protection to this segment of the stock which represents the prime breeding muskellunge. It also enabled a buildup of the spawning stock over the next four year period (1987-1990), with subsequent enhancements to recruitment based on strong year-classes occurring in 1991 and 1994. The dramatic turn-around in the Lake St. Clair muskellunge fishery emphasizes the need for, and benefit of, appropriate size-based regulations and effective angler catch-and-release initiatives. An angler diary program can make an extremely valuable contribution to management of muskellunge through the provision of comprehensive and cost-effective stock monitoring data. Favourable changes to musky habitat occurred during the same period but the habitat contribution to musky production and abundance, relative to changes in angling regulations and angler attitudes is unknown.

The muskellunge fishery of Escanaba Lake, Wisconsin, under liberalized angling regulations, 1946-1981

The muskellunge population in Escanaba Lake has been unregulated by angling size, season or bag limits from 1946 through 1981. To evaluate changes in the population under those conditions, the harvest, yield and exploitation of wild and stocked muskellunge were analyzed for the period 1946-1981. Collection of pertinent data was facilitated by a compulsory permit-type creel census in effect during the entire 36 year period. Harvest for fish age I and older averaged 25 fish annually over the entire period. From 1956 through 1981, the estimated population and exploitation rate for age II and older muskellunge averaged 47 fish and 29% respectively. For age IV and older fish during t his same period the mean annual harvest was 6 fish and the yield 70 pounds; the population estimate averaged 25 fish and the exploitation rate 29% Yearling stocking were nine times more effective at adding fish to the creel than fingerling stockings. Thirteen percent of the harvested muskellunge were creeled during the closed season for muskellunge on other Wisconsin waters and only 5% of the muskellunge were part of a bag containing more than one muskellunge. Only 23% of the total number of muskellunge harvested in this period were 30.0 inches or longer. The Escanaba Lake muskellunge population did not exhibit reductions in population size or annual harvest during the 36 years of angling without restrictions on size, season or bag.

Field evaluation and simulation modeling of length limits and their effects on fishery quality for muskellunge in the New River, Virginia

The trophy fisheries for Muskellunge (Esox masquinongy) in the northern U.S.A. and Canada often are developed and maintained by using high minimum‐length limits (MLL s). However, the effectiveness of using such MLL s on southern‐latitude Muskellunge populations, which have different rates of growth and mortality, warrants further research. The Muskellunge fishery in the New River, Virginia, was managed under a 30‐in (75 cm) MLL until 2006 when the MLL was increased to 42 in (105 cm) to increase the abundance of large Muskellunge. We measured fishery quality before and after the institution of the 42‐in MLL using size structure, average individual condition, rates of growth and mortality, and CPUE . We also assessed the potential of alternative length regulations (other MLL s and a 40–48‐in protected‐slot limit) to improve the population’s size structure and trophy production using simulation models in the Fisheries Analyses and Modeling Simulator (FAMS ) program. Following the institution of the 42‐in MLL , we observed a 5‐in increase in the average size of Muskellunge, an increase in the population’s size structure with greater proportions of memorable‐size individuals (≥42 in) and an increase in the abundance of memorable‐size Muskellunge. However, declines in the average condition, i.e., relative weight (W r ), of large Muskellunge (≥38 in) suggest there is possible stockpiling of individuals just below the 42‐in length limit. Higher MLL s (e.g., 48‐in MLL ) could further improve fishery quality by increasing the survival of Muskellunge to large trophy sizes (≥50 in). However, managers should be wary of stockpiling under alternative MLL s as well. Furthermore, a higher MLL is unlikely to garner broad angler support in this system. Conversely, a protected‐slot limit that allows the production of some trophy‐sized Muskellunge while reducing the overall number of individuals, and that limits potential for stockpiling, may be a more agreeable regulatory option for New River fishery managers. These findings and the methods described within this study may be useful for fisheries managers working on other Muskellunge fisheries in southern systems.

The importance in fishery management of leaving the big ones

Research by Berkeley et al. and by Bobko and Berkeley has recently demonstrated that older individuals of some fish species produce larvae that have substantially better survival potential than do larvae from younger fishes. These new findings augment established knowledge that larger individuals usually have exponentially greater fecundity. This is important because commercial fisheries and especially recreational fishing often target the larger fish. The protection of larger or older individuals is necessary for the sustainability of species currently exploited by humans.

Defecting fish population responses to a minimum size limit: Effects of variable recruitment and duration of evaluation

We used a simulation model to evaluate how recruitment variability and evaluation duration would affect fisheries managers’ ability to detect fish population responses to a minimum length limit. Length limits modeled were 254 mm for white crappie (Pomoxis annularis) and 305, 356, and 457 mm for largemouth bass (Micropterus salmoides). Simulations were conducted at recruitment variation (coefficient of variation, CV = 100 × SD/mean) of 20–100% for age‐1 recruits. We evaluated how population density, population biomass, total catch (fish harvested and released), yield, and proportional stock density (PSD) would differ in response to a single 3‐year or 5‐year length limit evaluation. For white crappies, simulations suggested that a 254‐mm length limit would not provide detectable differences (P > 0.10) in any population parameter if recruitment variability exceeded 90% for either evaluation period. Mean CV in recruits to age 0 or age 1 for empirical white crappie populations was 82% (range = 55–124, N = 14). Simulations revealed that largemouth bass populations would not exhibit detectable differences unless recruitment variability was 40% or less for a 305‐mm length limit and 65% or less for a 356‐mm length limit. Values of CV in recruits to age 0 or age 1 for largemouth bass populations averaged 66% (range = 11–189, N = 13). A 457‐mm length limit for largemouth bass provided detectable differences in total biomass and PSD up to recruitment variabilities of 100%. Detectable differences were more likely under 5‐year evaluations than 3‐year evaluations. Proportional stock density was the variable most likely to change in response to the size limit for both white crappies and largemouth bass. However, at recruitment variabilities greater than 90%, detectable differences did not occur in 3‐year or 5‐year evaluations, unless the size limit was 457 mm for largemouth bass. Fishery managers should consider effects of variable recruitment and duration of evaluation period when evaluating the success of a minimum length limit.

Efficacy of harvest and minimum size limit regulations for controlling short term harvest in recreational fisheries

It is important to consider the potential effectiveness of regulations for reducing total harvest levels when developing fishery management plans. A random forest (RF) modelling approach was used to examine how changing per‐angler harvest or minimum size limit regulations affected sport fishery harvest in US Atlantic coast recreational fisheries. Harvest limits per angler (i.e. bag limits) were typically high initially and subsequently reduced, whereas almost half of minimum length limits were initially below the length‐at‐maturity and subsequently increased. Across most fisheries examined, extreme reductions in harvest limits (e.g. from unlimited to catch‐and‐release) were largely ineffective at limiting total fishery harvest. Increasingly restrictive minimum length limits caused a greater average harvest reduction than per‐angler harvest limits. Some regulation changes were associated with higher angling effort and thus increased harvest, which suggests that when effort cannot be constrained, more direct harvest limitations should be considered.