Potential Direct and Indirect Effects of Climate Change on a Shallow Natural Lake Fish Assemblage

Much uncertainty exists around how fish communities in shallow lakes will respond to climate change. In this study, we modelled the effects of increased water temperatures on consumption and growth rates of two piscivores (northern pike [Esox lucius] and largemouth bass [Micropterus salmoides]) and examined relative effects of consumption by these predators on two prey species (bluegill [Lepomis macrochirus] and yellow perch [Perca flavescens]). Bioenergetics models were used to simulate the effects of climate change on growth and food consumption using predicted 2040 and 2060 temperatures in a shallow Nebraska Sandhill lake, USA. The patterns and magnitude of daily and cumulative consumption during the growing season (April–October) were generally similar between the two predators. However, growth of northern pike was always reduced (–3 to –45% change) compared to largemouth bass that experienced subtle changes (4 to –6% change) in weight by the end of the growing season. Assuming similar population size structure and numbers of predators in 2040–2060, future consumption of bluegill and yellow perch by northern pike and largemouth bass will likely increase (range: 3–24%), necessitating greater prey biomass to meet future energy demands. The timing of increased predator consumption will likely shift towards spring and fall (compared to summer), when prey species may not be available in the quantities required. Our findings suggest that increased water temperatures may affect species at the edge of their native range (i.e. northern pike) and a potential mismatch between predator and prey could exist

Predator-prey Interactions of Fishes in Two Nebraska Sandhill Lakes

Although largemouth bass Micropterus salmoides and northern pike Esox Lucius food habit studies have been undertaken extensively throughout the United States and Europe, none have been completed for fish communities in the Nebraska Sandhill lakes. Additionally, little information exists on the seasonal food habits of bluegill Lepomis macrochirus and yellow perch Perca flavescens in these shallow natural lakes. Most of the previous research on the Nebraska Sandhill lakes has focused on factors influencing quality panfish populations. Previous research indicated that largemouth bass relative abundance was positively correlated with bluegill and yellow perch proportional stock density (PSD). However, direct assessment of predator effects on panfish populations is still needed. The objective of my study was to determine seasonal food habits of bluegill, yellow perch, largemouth bass, and northern pike in Pelican and West Long lakes, Nebraska, in 2001. Although bluegill in all length groups primarily consumed macroinvertebrates during all seasons in West Long Lake, zooplankton were common in the diets of bluegills in all length groups during all seasons. In Pelican Lake, bluegills in all length groups fed almost exclusively on macroinvertebrates during all seasons rather than on zooplankton or fishes. Based on percent by number and weight, yellow perch in West Long Lake primarily fed on macroinvertebrates, while yellow perch in Pelican Lake additionally consumed zooplankton and fish (i.e., yellow perch). Based on percent by number and weight, largemouth bass in Pelican Lake primarily consumed yellow perch in all length groups and during all seasons. Although yellow perch were common in the diets of largemouth bass in West Long Lake, a greater variety of prey taxa appeared in their diets compared to bass in Pelican Lake. Northern pike in Pelican Lake fed primarily on yellow perch except in September when northern pike \u3e 710 mm consumed primarily common carp Cyprinus carpio. Although northern pike in West Long Lake fed primarily on yellow perch, a variety of prey fishes appeared in the diets of northern pike \u3c 350 mm. These results provide evidence of predator-prey interactions in Nebraska Sandhill lakes, which has only been inferred in previous research

FOOD HABITS OF YELLOW PERCH, \u3ci\u3ePERCA FLAVESCENS\u3c/i\u3e, IN WEST LONG LAKE, NEBRASKA

Food-habits data were collected from 102 yellow perch, Perca flavescens, in West Long Lake, Nebraska, from April to October, 2001, to determine iffood habits changed seasonally in this shallow, vegetated, natural lake. Based on percent by number and weight, yellow perch in all length groups and during all seasons primarily consumed macro-invertebrates. Yellow perch \u3c 130 mm in total length fed primarily on amphipods and chironomids in all months except October. For perch between 130 and 199 mm, amphipods and chironomids composed greater than 60% of the diet by weight in all months except August. Yellow perch ≥ 200 mm primarily consumed macro-invertebrates with fish contributing less than 6% ofthe diet by weight during all months except June. Knowledge of the trophic ecology of yellow perch in these lentic systems should help biologists better understand the role of perch as both predator and prey