Stephen B. Brandt

Changes in Diet and Body Condition of Lake Whitefish in Southern Lake Michigan Associated with Changes in Benthos

Abstract We evaluated the long-term trends of the benthic macroinvertebrate community (1980–1999) and biological attributes of lake whitefish Coregonus clupeaformis (1985–1999) in southeastern Lake Michigan. We also determined what food types were important to lake whitefish in an area where the amphipod Diporeia had not yet declined in 1998 and how the diet of lake whitefish changed as Diporeia declined during 1999–2000. Zebra mussels Dreissena polymorpha invaded the study area in 1992; Diporeia began to decline in 1993 and was nearly absent by 1999. The body condition of lake whitefish decreased after 1993 and remained low thereafter. The length at age and weight at age of lake whitefish was lower in 1992–1999 than in 1985–1991. After declines of Diporeia off the city of Muskegon, Michigan, between 1998 and 1999–2000, the proportion of Diporeia in the diet by weight fell from 70% to 25% and the percent occurrence decreased from 81% to 45%. In contrast, the proportion of lake whitefish that ate other pre...

Applications of Bioenergetics Models to Fish Ecology and Management: Where Do We Go from Here?

Abstract Papers and panel discussions given during a 1992 symposium on bioenergetics models are summarized. Bioenergetics models have been applied to a variety of research and management questions relating to fish stocks, populations, food webs, and ecosystems. Applications include estimates of the intensity and dynamics of predator–prey interactions, nutrient cycling within aquatic food webs of varying trophic structure, and food requirements of single animals, whole populations, and communities of fishes. As tools in food web and ecosystem applications, bioenergetics models have been used to compare forage consumption by salmonid predators across the Laurentian Great Lakes for single populations and whole communities, and to estimate the growth potential of pelagic predators in Chesapeake Bay and Lake Ontario. Some critics say that bioenergetics models lack sufficient detail to produce reliable results in such field applications, whereas others say that the models are too complex to be useful tools for ...

Spatially-explicit Models of Fish Growth Rate

Abstract Local density-dependent processes may significantly affect production dynamics at the population and ecosystem level. These processes are often nonlinear and occur at rates strongly influenced by the physical habitat. The spatial patchiness of both fish density and habitat has hampered our ability to separate the effects of density and habitat on production. In this paper, we introduce the concept of fish growth rate potential. Growth rate potential integrates physiologically-based models of fish growth rate with high-resolution spatial data on prey sizes, prey density, and the physical environment. By combining the strengths of bioenergetics models to simulate fish growth and of bioacoustics to measure fish density and size in a spatially-explicit framework, the approach overcomes some of the difficulties inherent in a spatially-patchy environment. The result is a two-dimensional, nonlinear model of fish growth and system production. Predator behavior and foraging algorithms provide additional m...

Predation by alewives on larvae of yellow perch in Lake Ontario

Abstract Alewives Alosa pseudoharengus preyed upon larval yellow perch Perca flavescens during late April and early May in a Lake Ontario embayment. Based on stomach analyses of 1,308 alewives collected during the springs of 1984–1986, predation on larval yellow perch occurred primarily at night in littoral areas during the 2 weeks immediately following peak hatch of yellow perch. Among stomachs of all alewives caught at night in littoral areas, 30% in 1985 (N = 43) and 41% in 1986 (N = 71) contained yellow perch larvae. Mean numbers of whole larvae per alewife stomach were 3.8 in 1985 and 32.6 in 1986. As many as 361 intact larval yellow perch were found in one stomach. Mean total lengths of yellow perch consumed on two dates in mid-May 1986 were 7.3 and 7.6 mm, compared to mean sizes of 8.0 and 8.6 mm of larvae living within the bay. We suggest predation by alewives on yellow perch larvae may reduce yellow perch recruitment in Lake Ontario as well as in other Great Lakes.

Influence of Diporeia Density on Diet Composition, Relative Abundance, and Energy Density of Planktivorous Fishes in Southeast Lake Michigan

Abstract The benthic amphipod Diporeia spp. is an important prey for many fish in offshore areas of the Great Lakes, but its abundance has been rapidly decreasing. To assess the influence of Diporeia availability on the food habits, relative abundance, and energetics of planktivorous fish, the diet composition, catch per unit effort (CPUE), and energy density of plantkivorous fish in southeast Lake Michigan during 2000–2001 were compared among locations with different Diporeia densities. Diporeia densities at St. Joseph, Michigan, were near 0/m2 over much of the bottom but averaged more than 3,800/m2 at Muskegon and Little Sable Point, Michigan. Consistent with these differences in Diporeia density, fish diet composition, CPUE, and energy density varied spatially. For example, alternative prey types comprised a larger fraction of the diets of bloater Coregonus hoyi, large (>100 mm total length) alewife Alosa pseudoharengus, and slimy sculpin Cottus cognatus at St. Joseph than at Muskegon and Little Sable ...

Evaluation of a Lake Whitefish Bioenergetics Model

Abstract We evaluated the Wisconsin bioenergetics model for lake whitefish Coregonus clupeaformis in the laboratory and in the field. For the laboratory evaluation, lake whitefish were fed rainbow smelt Osmerus mordax in four laboratory tanks during a 133-d experiment. Based on a comparison of bioenergetics model predictions of lake whitefish food consumption and growth with observed consumption and growth, we concluded that the bioenergetics model furnished significantly biased estimates of both food consumption and growth. On average, the model overestimated consumption by 61% and underestimated growth by 16%. The source of the bias was probably an overestimation of the respiration rate. We therefore adjusted the respiration component of the bioenergetics model to obtain a good fit of the model to the observed consumption and growth in our laboratory tanks. Based on the adjusted model, predictions of food consumption over the 133-d period fell within 5% of observed consumption in three of the four tanks...

Lake Erie hypoxia prompts Canada‐U.S. study

Because of its size and geometry, the central basin of Lake Erie, one of North Americas Great Lakes, is subject to periods in the late summer when dissolved oxygen concentrations are low (hypoxia). An apparent increase in the occurrence of these eutrophic conditions and ‘dead zones’ in recent years has led to increased public concern. The International Field Years for Lake Erie (IFYLE) project of the Great Lakes Environmental Research Laboratory (GLERL, a U.S. National Oceanic and Atmospheric Administration (NOAA) laboratory), was established in 2005 in response to this increase. This project is investigating the causes and consequences of hypoxia in the lake. As part of the effort, scientists from the United States and Canada conducted an extensive field study in 2005 to gather more information on the duration and extent of the hypoxic zone and its effects on the biota in the lake. This article gives a brief history and description of the problem and presents initial results from the field study.

A spatially-explicit approach for estimating carrying capacity: An application for the Atlantic menhaden (Brevoortia tyrannus) in Chesapeake Bay

A spatially-explicit methodology was developed for estimating system carrying capacities of fish stocks, and used to estimate the seasonal and spatial patterns of carrying capacity of Chesapeake Bay for Atlantic menhaden (Brevoortia tyrannus). We used a spatially-explicit three-dimensional (3-D) model that divided the heterogeneous habitat of Chesapeake Bay into over 4,000 cubes. Each cube represented a volume of water that was characterized by a specific set of environmental variables (phytoplankton biomass, temperature, and dissolved oxygen) driven by the 3-D water quality model. Foraging and bioenergetics models transformed the environmental variables into measures of potential growth rates of menhaden. Potential carrying capacity of menhaden was estimated as a function of phytoplankton production, menhaden consumption rate, and potential growth rate, combining phytoplankton production, thermal habitat, and menhaden physiology into one ecological value that is a measure of habitat quality from the perspective of the fish. Seasonal analysis of the Chesapeake Bay carrying capacity for Atlantic menhaden suggested two bottleneck periods: one in early June and a second during the fall. The bottleneck in carrying capacity was at about 10 billion age-0 fish. Annual recruitment of age-0 menhaden for the entire Atlantic coast of the U.S. ranged from 1.2–18.6 billion fish between 1955 and 1986. It appears that carrying capacity of, Chesapeake Bay does not limit the coastwide production of young menhaden. Any conditions such as nutrient reduction strategies, further eutrophication, or global climatic warming, that may influence the carrying capacity during the fall or early June periods, may ultimately alter coastwide abundance of menhaden through changes in Chesapeake Bay carrying capacity.

Feeding ecology of emerald shiners and rainbow smelt in central Lake Erie

ABSTRACT To better understand the feeding ecology of two important Laurentian Great Lakes prey species, rainbow smelt Osmerus mordax and emerald shiners Notropis atherinoides, we quantified the diet composition, selectivity, daily ration, and diet overlap of both species in offshore central Lake Erie during May through October 2005, which spanned a period of severe hypolimnetic hypoxia (<2 mg O2/L). Rainbow smelt fed upon a variety of prey taxa, including zooplankton, chironomid pupae and larvae, and fish, whereas emerald shiners primarily consumed cladocerans, if available. In turn, diet overlap between rainbow smelt and emerald shiners was low except during September when hypolimnetic hypoxia reduced rainbow smelt access to benthic prey. Rainbow smelt most frequently selected chironomid pupae, while emerald shiners generally selected pupae or large predatory cladocerans (Leptodora or Bythotrephes). Daily ration and individual consumption by rainbow smelt were 54–68% less during hypoxia than at the same site during stratified pre-hypoxic or mixed post-hypoxic conditions. Although emerald shiner daily ration and individual consumption decreased between pre-hypoxic and hypoxic periods, it continued to decrease during the post-hypoxic period, suggesting that reduced consumption may not have been linked to hypoxic conditions. Ultimately, our findings suggest that emerald shiners are as important regulator of zooplankton abundance in the Great Lakes as rainbow smelt, given their potentially high mass-specific consumption rates, selectivity and diet patterns, and current high abundance.

Movement of Largemouth Bass in Northern Chesapeake Bay: Relevance to Sportfishing Tournaments

Abstract Largemouth bass Micropterus salmoides have been displaced as far as 50 km from where they were caught in Chesapeake Bay tidewater angling tournaments. Two concerns are whether largemouth bass return to capture areas or whether they stockpile at tournament release sites. To answer these questions, movements of 82 largemouth bass tagged with radio transmitters and 146 largemouth bass tagged with streamer tags were observed during 1991–1995. Fish were collected by boat electrofishing near two disparate tournament weigh-in stations on the eastern and western shores of northern Chesapeake Bay. Some largemouth bass (43 radio-tagged, 58 streamer-tagged) were displaced 15–21 km to the other station; controls (39 radio-tagged, 88 streamer-tagged) were released where they were caught. Movement patterns were similar for displaced largemouth bass: 43% from the Susquehanna River (western shore) and 33% from the Northeast River (eastern shore) exhibited directed movement towards initial capture areas by return...