David G. Fielder

Environmental and Ecological Conditions Surrounding the Production of Large Year Classes of Walleye (Sander vitreus) in Saginaw Bay, Lake Huron

ABSTRACT The Saginaw Bay walleye population (Sander vitreus) has not fully recovered from a collapse that began in the 1940s and has been dependent on stocking with only limited natural reproduction. Beginning in 2003, and through at least 2005, reproductive success of walleye surged to unprecedented levels. The increase was concurrent with ecological changes in Lake Huron and we sought to quantitatively model which factors most influenced this new dynamic. We developed Ricker stock-recruitment models for both wild and stock fish and evaluated them with second-order Akaikes information criterion to find the best model. Independent variables included adult alewife (Alosa pseudoharengus) abundance, spring water temperatures, chlorophyll a levels and total phosphorus levels. In all, 14 models were evaluated for production of wild age-0 walleyes and eight models for stocked age-0 walleyes. For wild walleyes, adult alewife abundance was the dominant factor, accounting for 58% of the variability in age-0 abundance. Production of wild age-0 fish increased when adult alewives were scarce. The only other plausible factor was spring water temperature. Predictably, alewife abundance was not important to stocked fish; instead temperature and adult walleye abundance were more significant variables. The surge in reproductive success for walleyes during 2003–2005 was most likely due to large declines in adult alewives in Lake Huron. While relatively strong year classes (age-1 and up) have been produced as a result of increased age-0 production during 2003–2005, the overall magnitude has not been as great as the initial age-0 abundance originally suggested. It appears that over-winter mortality is higher than in the past and may stem from higher predation or slower growth (lower condition for enduring winter thermal stress). From this it appears that low alewife abundance does not assure strong walleye year classes in Saginaw Bay but may be a prerequisite for them.

Examination of Factors Contributing to the Decline of the Yellow Perch Population and Fishery in Les Cheneaux Islands, Lake Huron, with Emphasis on the Role of Double-crested Cormorants

ABSTRACT Double-crested cormorants increased exponentially in the Les Cheneaux Islands area during the 1980s and 1990s. The yellow perch fishery and population declined by the late 1990s and finally collapsed in 2000. Previous research confirmed that cormorants fed seasonally on perch. This analysis sought to use creel survey data and data from an annual gillnet collection to characterize the perch fishery and population during this time so as to explore if declines were a result of declining recruitment or increased mortality or both. Regression analysis explored six possible independent variables to account for yellow perch trends. Yellow perch abundance and its fishery declined throughout the Les Cheneaux Islands. Mean age declined which was consistent with a high mortality rate explanation. Yellow perch recruitment, as indicated by gillnet catch rate of age-2 perch, continued during this time including one very strong year class. Total annual mortality rates determined by the cohort method were as high as 85% during much of this time and increased over the time series. Cormorant abundance accounted for a total of five significant relationships with the yellow perch data, more than any other independent variable. From this, it is apparent that cormorant predation is at least one factor affecting the perch population and fishery and may be the most influential force, among those examined, during this time series.

Acoustic telemetry reveals large-scale migration patterns of walleye in Lake Huron

Fish migration in large freshwater lacustrine systems such as the Laurentian Great Lakes is not well understood. The walleye (Sander vitreus) is an economically and ecologically important native fish species throughout the Great Lakes. In Lake Huron walleye has recently undergone a population expansion as a result of recovery of the primary stock, stemming from changing food web dynamics. During 2011 and 2012, we used acoustic telemetry to document the timing and spatial scale of walleye migration in Lake Huron and Saginaw Bay. Spawning walleye (n = 199) collected from a tributary of Saginaw Bay were implanted with acoustic tags and their migrations were documented using acoustic receivers (n = 140) deployed throughout U.S. nearshore waters of Lake Huron. Three migration pathways were described using multistate mark-recapture models. Models were evaluated using the Akaike Information Criterion. Fish sex did not influence migratory behavior but did affect migration rate and walleye were detected on all acoustic receiver lines. Most (95%) tagged fish migrated downstream from the riverine tagging and release location to Saginaw Bay, and 37% of these fish emigrated from Saginaw Bay into Lake Huron. Remarkably, 8% of walleye that emigrated from Saginaw Bay were detected at the acoustic receiver line located farthest from the release location more than 350 km away. Most (64%) walleye returned to the Saginaw River in 2012, presumably for spawning. Our findings reveal that fish from this stock use virtually the entirety of U.S. nearshore waters of Lake Huron.

Evaluation of Stocking Walleye Fry and Fingerlings and Factors Affecting Their Success in Lower Lake Oahe, South Dakota

Abstract Recruitment of stocked fry and fingerlings of walleye Stizostedion vitreum to the population, and influences of available forage and water temperature on stocking success, were evaluated with gillnetting and forage sampling in stocked embayments. Walleye fingerling stocking was found to make a significant contribution to the fall young-of-year population, whereas fry stocking had no effect. Levels of zooplankton biomass increased seasonally from low levels at the time of fry stocking (<30 mg/m3) to much higher levels by the time of fingerling stocking (93 mg/ m3). Water surface temperature correlated closely with zooplankton increases and averaged 15°C at the time of fingerling stocking. Although other undetermined factors (such as predation) may have influenced survival of stocked fish, the zooplankton biomass levels appeared to affect fingerling survival. In addition, low zooplankton levels perhaps were involved in the failure of stocked fry. Abundance of littoral-zone forage fish was not a det...

Evaluation of Two Forms of Electroanesthesia and Carbon Dioxide for Short-Term Anesthesia in Walleye

Abstract Anesthetics immobilize fish, reducing physical damage and stress during aquaculture practices, stock assessment, and experimental procedures. Currently, only tricaine methanesulfonate (MS-222) is approved for use as an anesthetic for food fish in Canada and the United States; however, MS-222 can only be used with certain fish species, and treated fish must be held for a specified period of time before release into the wild. Two forms of electroanesthesia and carbon dioxide (CO2) were evaluated as anesthetics for adult walleye Sander vitreus to determine their suitability for use before intracoelomic implantation of telemetry transmitters. Walleyes were subjected to one of three treatment groups: constant direct current (CDC), pulsed direct current (PDC), and CO2. Fish subjected to these treatments were monitored for induction (where appropriate) and recovery time and whether these forms of anesthesia were conducive to implanting telemetry transmitters, that is, whether they fit a surgery threshol...

Angler-Caught Piscivore Diets Reflect Fish Community Changes in Lake Huron

AbstractExamination of angler-caught piscivore stomachs revealed that Lake Trout Salvelinus namaycush, Chinook Salmon Oncorhynchus tshawytscha, and Walleyes Sander vitreus altered their diets in response to unprecedented declines in Lake Hurons main-basin prey fish community. Diets varied by predator species, season, and location but were nearly always dominated numerically by some combination of Alewife Alosa pseudoharengus, Rainbow Smelt Osmerus mordax, Emerald Shiner Notropis atherinoides, Round Goby Neogobius melanostomus, or terrestrial insects. Rainbow Trout Oncorhynchus mykiss (steelhead), Coho Salmon Oncorhynchus kisutch, and Atlantic Salmon Salmo salar had varied diets that reflected higher contributions of insects. Compared with an earlier (1983–1986) examination of angler-caught predator fishes from Lake Huron, the contemporary results showed an increase in consumption of nontraditional prey (including conspecifics), use of smaller prey, and an increase in insects in the diet, suggesting that ...

Long-Term and Interannual Dynamics of Walleye and Yellow Perch in Saginaw Bay, Lake Huron

Abstract Walleye Sander vitreus and yellow perch Perca flavescens are well-studied, ecologically important fish species that co-occur in a wide range of systems and experience complex interactions; on the one hand, they are physiologically and ecologically similar and therefore may respond analogously to environmental variation, while on the other hand they interact antagonistically as competitors, predators, and prey. In Saginaw Bay, Lake Huron, walleyes and yellow perch have supported a combination of commercial and recreational fisheries and have been exposed to a series of ecosystem-level stressors and management actions that may have impacted these populations via multiple pathways. We used dynamic factor analysis and correlation analysis of walleye and yellow perch annual fall trawl catch data to elucidate the overall trends in walleye and yellow perch populations in Saginaw Bay. The results suggest that walleyes and yellow perch trend differently; while the relative abundance of age-0–2 walleyes ge...

Response of yellow perch in Les Cheneaux Islands, Lake Huron to declining numbers of double-crested cormorants stemming from control activities

ABSTRACT The yellow perch (Perca flavescens) fishery of the Les Cheneaux Islands region of Lake Huron experienced an unprecedented collapse in 2000. Immediately prior to the collapse was the proliferation of double-crested cormorants (Phalacrocorax auritus) in the area. Subsequent investigations established that double-crested cormorant predation was chief among the forces shaping the local yellow perch population and contributing to the collapse of the fishery. A double-crested cormorant control program was implemented in 2004 with the objective of benefiting the yellow perch population and fishery. This study used creel survey and gillnet fish community assessment data to evaluate the response of the yellow perch population and fishery. In all, seven key yellow perch metrics were analyzed using regression analysis with double-crested cormorant abundance as the independent variable. As double-crested cormorant abundance declined, yellow perch abundance increased, total mortality rate decreased, the angler catch rate and harvest in the recreational fishery improved, yellow perch growth rate declined and mean age increased. Increased yellow perch recruitment was documented since 2003 but it was the longevity of these year classes, (improved survival) as much or more than their magnitude of the year class, that allowed for the progress towards recovery. Questions facing managers are the sustainable level of double-crested cormorants in the region and the long term prognosis for the yellow perch fishery to fully recover to pre—double—crested cormorant levels.

Sources of Walleye Recruitment in Saginaw Bay, Lake Huron

Abstract Historically, the fishery for walleyes Stizostedion vitreum in Saginaw Bay was among the largest in the Great Lakes, second only to that of Lake Erie, but it collapsed in 1944 because of a series of year-class failures attributed to degradation of spawning habitat and declines in water quality. I determined the condition and use of reef habitat by spawning walleyes (thought to be historically important for reproduction) and the contributions to recruitment by hatchery walleyes, which were stocked as fingerlings beginning in the early 1980s. Reef surveys confirmed that nearly all inner bay reefs were of low quality, apparently degraded by sedimentation. Reef habitat quality in the outer portion of the bay and two marginal reefs in the southeastern portion of the bay was reasonably good, but the reefs were used only sparsely by walleyes. Oxytetracycline-marked hatchery fish composed an average of 79% of the locally produced recruits of the 1997, 1998, and 1999 year-classes. I concluded that the mod...

Relationship between Walleye Fingerling Stocking Density and Recruitment in Lower Lake Oahe, South Dakota

Abstract This study evaluated four methods ofexpressing fingerling stocking density for walleye Stizostedion vitreum: number per surface area, number per littoral-zone area, number per shoreline development value, and number per shoreline distance, Walleye fingerlings were stocked in embayments of lower Lake Oahe in 1988 and 1989 at varying densities. Stocking success was assessed by means of fall gillnetting for young-of-year walleyes. Mean gill-net catch rates varied significantly within each method of expressing stocking density. Effects of stocking density on gill-net catch rate for walleye young of the year were analyzed with linear regression. Fingerling densities expressed as number per shoreline development value had the highest coefficient of determination. Shoreline development value may provide a better measure of walleye fingerling habitat than traditional expressions of stocking density such as number per surface area. Based on this assessment, a minimum stocking density of 17,006 fingerlings...