Fig 1 - uploaded by David Fielder
Content may be subject to copyright.
Map of Saginaw Bay identifying locations where cormorant colonies were located; Spoils Island and Little Charity Island.
Source publication
Stakeholders and fishery managers expressed concern that double-crested cormorant Phalacrocorax auritus predation may be a factor in the recent poor survival of yellow perch Perca flavescens in Saginaw Bay. We quantified cormorant diets from two nesting colonies in Saginaw Bay during April–September in 2013 and 2014, with special emphasis on impact...
Contexts in source publication
Context 1
... Bay (Fig. 1) is a large (2947 km 2 ) shallow bay in the Michigan waters of Lake Huron that ranges from an average depth of approximately 4.6 m in the inner bay to 14.6 m in the outer bay. Saginaw Bay has a number of islands, with Little Charity and Spoils islands used by nesting cormorants. As with much of the Great Lakes, the number of cormorants ...
Context 2
... were collected from two areas in Saginaw Bay, near Little Charity Island (outer Saginaw Bay) and Spoils Island (inner bay near the Saginaw River mouth) (Fig. 1). Collections were made by USDA Animal and Plant Health Inspection Service, Wildlife Services using shotguns when birds returned to the nesting colonies to increase the probability of full stomachs. Approximately 25 birds were collected monthly at each nesting colony from 26 April-16 September (2013) and from 06 May-19 September ...
Citations
Understanding inter-annual variation in the density of young-of-the-year fish is an important tool for assessing stock status and guiding management decisions. We analyzed data spanning from 2003 to 2022 collected at Lipno Reservoir in Czechia. The study aimed to identify factors influencing the density of pikeperch (Sander lucioperca), a valuable predatory fish species in European waters. A bimodality test for the size class distribution has revealed the existence of two distinct YOY cohorts: extremely small (ES) and ordinary fingerlings. Using the Bayesian horseshoe prior method with 37 potential predictors, followed by linear regression, we observed that certain environmental factors similarly influenced both cohorts. Higher temperatures during spring and summer, coupled with increased densities of large and medium-sized cladocerans, positively affected the density of both cohorts. However, distinct influences were observed: for ordinary fingerlings, increased summer precipitation and a lower abundance of predators were beneficial, whereas, for ES fingerlings, summer copepod density emerged as an additional positive factor. This study emphasizes the importance of a detailed investigation of factors influencing pikeperch recruitment. Examining these drivers provides a clearer insight into the causes of variations in the early life stage, which is crucial for monitoring and managing populations in temperate reservoirs.
Saginaw Bay is a large coolwater region of Lake Huron and Walleye Sander vitreus is the apex predator. From the time of first settlement to the mid-1940s, the bay's Walleye population was the target of a loosely regulated commercial fishery characterized by periods of overharvest and recovery but was sustained for more than half a century at an average annual yield of about 495 metric tons. The fishery collapsed due to a series of year-class failures attributed to declining water quality, habitat degradation, and effects of invasive species. The degraded and collapsed condition lasted until the early 1980s. With improving water quality stemming from clean water legislation and the closure of the commercial fishery, a new period of improvement was achieved. Walleye fingerling stocking was implemented and a recreational fishery soon emerged. Research and assessment sought to monitor stock mortality , growth, and exploitation rates as well as contribution of stocked fish to the fishery. Recovery plans were drafted that sought to improve spawning habitat and improve survival of Walleye fry by creating a predation barrier to the predatory effects of the invasive Alewife Alosa pseudoharengus through increased Walleye stocking. A series of cascading food-web changes took place in Lake Huron, resulting in the sudden collapse of Alewives, and Walleye natural reproduction surged beginning in 2003. Walleye stocking was discontinued in 2006 and recovery targets were first achieved in 2009. Management and research shifted from recovery efforts to enhanced stock assessment efforts and modeling, a clear sign of success! Key lessons learned include (1) eliminating or at least reducing obstacles to reproduction (such as habitat and water quality) are essential first steps to laying the foundation for recovery, (2) maintaining populations (via of stocking in this instance) will help ensure that broodfish are available for spawning when conditions improve, (3) ecosystems are resilient and when released from stressors (Alewives in this instance) natural processes can resume, (4) great value exists in survey/assessment investment and long-term data sets for guiding restoration, and (5) resolve and commitment by natural resource professionals, administrators, and stakeholders is critical for sustaining restoration efforts and the investment they require.
Status and Trends of the Fish Community of Saginaw Bay, Lake Huron 2012–2017
This is a periodic report on the fishery independent survey of fish community status performed annually by the Michigan DNR since 1971.
Double‐crested cormorant Phalacrocorox auritus Lesson (cormorant) populations have increased throughout the Great Lakes region of North America causing concern related to the impact of cormorant predation on fish communities. A recent decline in yellow perch Perca flavescens (Mitchill) abundance within the Lake Winnebago System, Wisconsin, USA, prompted an assessment of cormorant diets to evaluate potential effects of cormorant predation on the sportfish community. Diets were collected from 883 cormorants (417 from Lake Winnebago and 466 from Lake Butte des Morts) between 2015 and 2017. Cormorant diets on both waterbodies consisted mostly of freshwater drum Aplodinotus grunniens Rafinesque and gizzard shad Dorosoma cepedianum (Lesueur). Yellow perch and walleye Sander vitreus (Mitchill) observations were infrequent and represented < 5% of cormorant diets by weight each year. Under current conditions, cormorant predation likely has minimal impact on the Lake Winnebago sportfish community, but more research is needed to assess potential impacts on Lake Butte des Morts.
