Spawning season distribution in subpopulations of muskellunge in Georgian Bay, Lake Huron

Loss of spawning and nursery habitats has been implicated as a major factor in the widespread decline of Muskellunge (Esox masquinongy) populations in North America. Although there is limited evidence of spawning site fidelity in Great Lakes populations of Muskellunge, such behavior could result in recruitment failure if individuals return each year to spawning sites that have become degraded. We compared the spawning behaviors of individual Muskellunge across three subpopulations in Georgian Bay, Lake Huron, to address the hypothesis that the use of specific spawning sites and spawning site fidelity are independent of the habitat’s suitability for successful recruitment. The study regions (southeastern, northeastern, and northern Georgian Bay) have experienced different impacts from human development and sustained low water levels. We radio‐tagged 49 adult Muskellunge and tracked them for up to 3 years (between 2012 and 2015). Sufficient multiyear data were only acquired for 18 individuals in the southeastern region; among those fish, 16 showed fidelity to at least one activity center over 2–3 years. Male Muskellunge occupied significantly smaller activity centers and shallower depths than females during the spawning season. The locations of adult Muskellunge were in close proximity to current and historic nursery sites that had been identified in each region by other studies, supporting the close spatial linkage between spawning habitat and nursery habitat. This study is the first to confirm spawning site fidelity in Georgian Bay Muskellunge, and our results support the spatial association between spawning and nursery habitats. The repeated use of degraded habitat by spawning adults, as appears to be the case in southeastern Georgian Bay, highlights the need to identify and protect spawning and nursery habitats.

Northern pike and muskellunge spawning ecology and reproductive success in the lower Ottawa River

Spawning (1995) and reproductive success (1994 and 1995) of northern pike (Esox lucius) and muskellunge (Esox masquinongy) were compared in two bays (Martin and Pentecôte) and one tributary (Kinonge River) of the Carillon Reservoir on the Ottawa River. Eggs collected in 60 cm x 60 cm baskets served to determine spawning sequences and differential utilization of habitat. The northern pike spawning sequence was similar at the three sites, the peak occurring between April 20 and 27. Muskellunge spawning peaked two weeks later in the Kinonge river (May 12-17) than in the two bays (April 27-May 5). Martin Bay had a second spawning peak during the May 16-19 interval. In the Kinonge River, northern pike egg deposition was more frequent in lentic, shallow, vegetated turbid sectors and on clay and silt dominated substrates whereas muskellunge egg deposition was more frequent in lotic, less turbid sectors on sand substrates with no vegetation present. Spawning habitat segregation was less pronounced in the two bays where trends in egg deposition of both species relative to environmental variables was more similar. Young-of-the-year seine catches–per-unit-of-effort suggest that northern pike reproductive success was nil in Martin Bay in 1994 and 1995; good in Pentecôte Bay and in the Kinonge River in 1994 but very low in 1995. Muskellunge reproductive success was good in both years in the Kinonge River but negligible in the two bays.

Sperm production and spawning success for muskellunge and northern pike

Sperm production and success of natural fertilization were examined for both muskellunge and northern pike to assess their potential importance in natural reproduction. The annual cycle of spermatogenesis, the relative sizes of the testes and the production of spermatozoa were determined for both species. Mature testes in muskellunge weigh less than half those of northern pike of the same size. The density of spermatozoa within the testes of muskellunge was about 7% less than for northern pike.

The viability of naturally spawned eggs of both species was determined by collecting eggs with trays and handnets in 1960 and 1964. Fertilization rates of 47.2% and 70.6% were determined for two collections of northern pike eggs on trays. Fertilization rates of newly spawned muskellunge eggs ranged from 30.0% to 88.4% for three tray collections. Slightly less than 50% of these eggs remained alive after 3-4 days laboratory incubation in aerated water. The viability of eggs collected with hand nets from Anacharis beds was low. Predation by minnows caused significant egg mortality at one site.

Spawning and post-spawning movements of the St. Lawrence River muskellunge (Esox masquinongy)

Radiotelemetry tracking of adult muskellunge (Esox masquinongy) was used to locate muskellunge spawning and nursery habitats in the Thousand Islands region of the St. Lawrence River and to describe post-spawning movements. From 1984 to 1989, 47 adult muskellunge were radio tagged during the spawning season at 22 sites. Radio-tagged fish were located at least once daily during the spawning period. Capture sites of adult muskellunge and areas frequented by tagged muskellunge during the spawning period were subsequently seined to document the presence or absence of young-of-the-year (YOY) muskellunge. YOY muskellunge were collected at 13 of the 22 adult capture sites and also at an additional 14 sites frequented by radio tagged adults. Post-spawning muskellunge generally either migrated upstream to Lake Ontario, remained in the vicinity of their respective spawning site or moved into deep water where they could not be located. Radio transmitters that functioned into the following season revealed a high degree of reproductive homing.

Identification of principal spawning areas and seasonal distribution and movements of muskellunge in Leech Lake, Minnesota

Six specific muskellunge spawning locations were documented and preferred spawning habitat was determined by surgically implanting radio transmitters in 14 adult muskellunge capture by angling in summer 1979. Adult fish from each of thre areas on the lake were radio-tagged. Spawning sites were distinctly offshore in depths of 1 to 2 m over a soft calcareous substrate with Chara spp. as the dominant vegetation. Physical characteristics of the six examined areas were very similar even though widely separated geographically. Selection for these sites occurred even though a wide variety of habitat types was available. Mean tracking time for 12 fish was 396 days which included the 1980 spawning period. Significant differences relating to home range and movement were observed for muskellunge inhabiting disparate environments within the lake. Muskellunge residing tin the main basin occupied total home ranges which were five times larger than of those fish inhabiting Walker Bay. The main lake fish also tended to have winter home ranges distinctly separate from summer ranges and winter home ranges were larger than summer ones by a factor of nearly two. Walker Bay fish had winter home ranges which were smaller than those of summer by a factor of over six and were contained within the summer ranges. Survival of all angler-caught fish additionally subjected to implant surgery strongly suggest that catch and release of muskellunge is a realistic management option.

Lake characteristics influencing spawning success of muskellunge in northern Wisconsin lakes

We determined the physical, chemical, biological, and land use characteristics that distinguish northern Wisconsin lakes with self‐sustaining populations of muskellunge Esox masquinongy from lakes where stocking is required to maintain populations. Lakes that supported self‐sustaining muskellunge populations were characterized by fewer shoreline alterations and by spawning habitats with softer, organic‐nitrogen‐rich sediments. Lakes that required stocking had extensively developed shorelines. The direction of water level change during the spawning period, percentage of spawning area sediment covered by woody debris, number of deadfall trees per kilometer of shoreline, and percentage of shoreline that was totally developed were the most important variables for classifying the level of muskellunge reproduction a lake could support. A linear discriminant function correctly classified 83% of the lakes with self‐sustaining muskellunge populations and 89% of the lakes requiring stocking to sustain or enhance muskellunge populations. Lake managers wishing to use muskellunge stocking programs to reestablish self‐sustaining populations should critically review each candidate lake by considering our model and that of Dombeck et al. (1986).

Oocyte recruitment and spawning chronology in pike (Esox lucius) and muskellunge (E. masquinongy)

During the reproductive cycle, the progression of oogenesis differs markedly between northern pike, Esox lucius Linnaeus, and muskellunge, Esox masquinongy Mitchill. Both species have group-synchronous ovaries but have different oocyte recruitment strategies. Pike is a single spawner, developing eggs in a single clutch annually, whereas muskellunge is a fractional spawner, producing two clutches of eggs per year. During the spawning period in large female muskellunge, oocyte counts indicate that the second clutch of eggs is equally important to the first. An event portrait of the spawning period for muskellunge is provided, whereby amval of adults to a spawning site, egg yield, and hatching success agree with the fractional spawner concept. A hypothesis of the temporal sequence of evolutionary relationships in recruitment of oocytes for esocoid fishes is presented. The reproductive strategy of muskellunge belongs to a common esocoid ancestor, whereas that in pike is derived and unique. The significance of this divergence in closely related species remains consistent with the ecological theory that evolution of reproductive strategies is adaptive to diverse environmental conditions.

Spring capture site fidelity of adult muskellunge in inland lakes

Behaviors that affect the distribution of fish within aquatic systems are important considerations in the design of sampling programs. Although movements consistent with reproductive homing have been documented for muskellunge Esox masquinongy in relatively large, complex systems, quantitative data describing their distribution at the restricted spatial scale relevant to small lake fisheries are lacking. We sampled muskellunge by means of fyke netting over 2 years in each of four Wisconsin lakes with surface areas between 110 and 588 ha. Individual capture locations were recorded. Each muskellunge sampled during the first year was injected with a passive integrated transponder to allow identification of the individuals recaptured during the second year. The number of recaptures with functional transponders during the second year ranged from 15 to 43 per lake. Capture site fidelity, defined as the percentage of recaptured fish being found in the same spawning area in two consecutive years, varied from 55% to 93%. The results are relevant to population estimation and broodstock collection for artificial propagation. Population estimates need to include all spawning habitats because marked and unmarked fish are not well mixed throughout the lake during the spawning season. Because repeated netting effort at the same locations among years is likely to resample individuals used for broodstock collection, netting effort should be dispersed among spawning sites.

Reproductive success of sympatric northern pike and muskellunge in an upper St. Lawrence River bay

A change in the use of spawning habitats linked with water-level management may explain differences in reproductive success among sympatric St. Lawrence River northern pike Esox lucius and muskellunge Esox masquinongy. Reproductive success in a shared spawning and nursery bay was compared based on egg (embryo) and age-0 abundance estimates before the fall emigration of young. Historically, northern pike were noted to commence spawning runs in shallow flooded areas soon after ice-out. I found that more than 87% of the estimated northern pike egg deposition in 1994 occurred in offshore, deep-water habitats (2–5 m) and that 99% did in 1995. Northern pike began spawning 17 d before muskellunge in 1994 and 31 d earlier in 1995. Spawning peaks occurred during the interval of 16–23 May. Muskellunge mostly spawned near shore (<1.5-m depth) in submerged aquatic vegetation growth that was absent during northern pike spawning. Muskellunge spawning began and peaked between 23 May and 4 June in 1994 and between 23 May and 1 June in 1995. Estimated egg deposition by northern pike was over 40 times that of muskellunge for the 2 years combined. Despite greater egg deposition, minimum survival estimates of northern pike from egg to fall juvenile were very low: 0.00008% in 1994 and 0.00010% in 1995. By comparison, minimum muskellunge survival estimates (egg to fall juvenile) were greater: 0.034% in 1994 and 0.105% in 1995. In seine surveys age-0 muskellunge catch per unit effort was negatively correlated with that of northern pike (r = −0.77), and muskellunge dominated catches for 9 of 10 years sampled. Growth of inshore submergent habitat during muskellunge spawning and the low abundance of northern pike may have contributed to the greater reproductive success of muskellunge.

Reproductive homing in muskellunge (Esox masquinongy)

The number and nature of muskellunge moving to and from spawning grounds are extensively documented. Individual spawning muskellunge in Stony Lake, Ontario are considered to home annually to specific spawning grounds and to specific areas (spawning sites) within spawning grounds. Some individuals were caught in the same location, or a nearby location, in as many as 7 yr. There is some evidence for discrete populations with apparent reproductive isolation and no interchange in summer. Dispersal from spawning grounds to summer home ranges seems to be limited in regard to direction and area sf the lake. Recapture of fish on spawning grounds suggests an obligatory return to a limited number of “traditional” spawning grounds and may extend our knowledge of the groups of fishes exhibiting this type of directed movement. The results also have serious implications for muskellunge in regard to management, shoreline development, and genetic contamination by fish culture activities.