Round Goby Predation on Smallmouth Bass Offspring in Nests during Simulated Catch-and-Release Angling

Round goby Neogobius melanostomus first appeared in Lake Erie in 1993 and now occur in extremely high densities in some areas. As known nest predators, round goby currently pose a threat to nest-guarding smallmouth bass Micropterus dolomieu. We conducted manipulative experiments to evaluate the combined effects of round goby predation and catch-and-release angling during 1999–2001 in the Bass Islands, Lake Erie. We quantified how many smallmouth bass offspring were consumed by round goby when nest-guarding smallmouth bass males were present, removed, and recovering from angling-related stress. In 10 h of video observations, we only saw one instance of round goby consuming smallmouth bass offspring while the nest was guarded. Upon removal of nest-guarding smallmouth bass, round goby quickly entered unguarded nests (4.3 round goby/min for nests with unhatched embryos and 1.8 round goby/min for nests with hatched embryos). During experimental catch-and-release angling, round goby consumed an average of 2,000 unhatched embryos before the guardian male returned, but postreturn offspring losses were minimal while the male recovered from angling stress. For an average smallmouth bass nest in the Bass Islands, round goby could consume all offspring from an unguarded nest in about 15 min. Round goby predation and smallmouth bass angling combined to reduce survival of smallmouth bass embryos, but we did not observe round goby consuming free-swimming larvae or juveniles. If the number of surviving smallmouth bass embryos drives adult population size, managers should consider angling regulations that reduce interference with nesting males, thus limiting the deleterious effects of round goby.This research was funded by Federal Aid in Sport Fish Restoration Project F-69-P, administered jointly by the U.S. Fish and Wildlife Service and the Ohio Department of Natural Resources, Division of Wildlife, and the Department of Evolution, Ecology, and Organismal Biology at Ohio State University

Increased parental care cost for nest-guarding fish in a lake with hyperabundant nest predators

Although parental care increases offspring survival, providing care is costly, reducing parental growth and survival and, thereby, compromising future reproductive success. To determine if an exotic benthic predator might be affecting parental care by nest-guarding smallmouth bass (Micropterus dolomieu), we compared nest-guarding behavior and energy expenditures in two systems, one with a hyperabundant recently introduced predator, the round goby (Neogobious melanostomus). In Lake Erie, USA, smallmouth bass vigorously defended their nests from benthic round gobies. In Lake Opeongo, Canada, smallmouth bass were exposed to fewer and predominantly open-water predators and were less active in their nest defense. From scuba and video observations, we documented that nest-guarding smallmouth bass chased predators (99% of which were round gobies) nine times more frequently in Lake Erie than in Lake Opeongo. This heightened activity resulted in a significant decline in weight and energetic content of guarding males in Lake Erie but no change in Lake Opeongo males. Bioenergetic simulations revealed that parental care increased smallmouth bass standard metabolic rate by 210% in Lake Erie but only by 28% in Lake Opeongo. As energy reserves declined and offspring became increasingly independent, males in both lakes consumed more prey and spent more time foraging away from their nests; however, nest-guarding smallmouth bass consumed few prey and, in Lake Erie, rarely consumed round gobies. Therefore, increased parental care costs owing to the presence of round gobies could affect future growth, reproduction, and survival if smallmouth bass approach critically low energy reserves.Funding for this project was provided by Federal Aid in Sport Fish Restoration Project F-69-P, administered jointly by United States Fish and Wildlife Service and Ohio Department of Natural Resources, Division of Wildlife, a Sigma Xi Grant-in-Aid awarded to G.B.S., and the Department of Evolution, Ecology, and Organismal Biology at The Ohio State University

Winter Ecology of Kokanee: Implications for Salmon Management

We sampled various limnological parameters and measured growth and diet of age-0 kokanee Oncorhynchus nerka (lacustrine sockeye salmon) during two winters in a high-mountain lake of the Sawtooth Valley, Idaho. Although winter has been recognized as an important period for many warmwater fishes and for stream-dwelling salmonids, winter limitations have only recently been studied for coolwater and coldwater species. Ice and snow cover in winter limited light penetration. As a result, chlorophyll-a and zooplankton density were lower in ice-covered periods than during ice-free periods. The weight of stomach contents was often below a maintenance ration, yet the incidence of empty stomachs was extremely low (1 of 63) and the weight of stomach contents increased as energy reserves declined, indicating that kokanee were actively foraging during winter. Kokanee length and weight remained constant during the winter of 1993–1994 but increased from November through May in 1994–1995. Condition factors, however, declined significantly over the winter in both years, and lipid content approached levels associated with mortality. Differences in growth patterns may have been caused by a combination of changes in zooplankton density and kokanee abundance and in kokanee behavior to defend energy reserves or avoid predation. Results demonstrated the ambiguity of some growth measurements and the importance of choosing the correct metric for measuring growth in fishes. Because juvenile kokanee and sockeye salmon are ecologically similar, management efforts to restore the endangered Snake River sockeye salmon to the Sawtooth Valley lakes should recognize that winter conditions might be a bottleneck for this species

Effects of storms, angling, and nest predation during angling on smallmouth bass (Micropterus dolomieu) nest success

Abstract in English and FrenchWe studied how storms, angling, and nest predation during angling affected smallmouth bass (Micropterus dolomieu) nest survival in the Bass Islands, Lake Erie, Ohio, USA. Increasing angler effort and introduction of an exotic nest predator, round goby (Neogobious melanostomus), have raised concerns about smallmouth bass recruitment in Lake Erie. We surveyed smallmouth bass nests and calculated daily survival rates for nests assigned to different angling treatments: control, angling without predation, or angling with predation treatments. Only 30% of control nests were successful compared with 11% of angling without predation and 14% of angling with predation treatments. We used the Mayfield method and maximum likelihood models in the program MARK to estimate the survival rates for nests of different treatments and exposed to different numbers of storms. Although nest predators consumed about 35% of broods during angling, daily nest survival rates of both angling treatments were similar. Angling reduced nest survival compared with controls by approximately 5%. Storms reduced both nest success and daily survival. The best model predicting daily nest survival included the added effects of angling treatment and number of storms. Thus, whereas storms and angling affected smallmouth bass nest survival, nest predation during angling did not.This research was funded by Federal Aid in Sport Fish Restoration Project F-69-P administered jointly by the US Fish and Wildlife Service and Ohio Department of Natural Resources, Division of Wildlife, and the Department of Evolution, Ecology, and Organismal Biology at Ohio State University

Increased parental care cost for nest-guarding fish in a lake with hyperabundant nest predators

Although parental care increases offspring survival, providing care is costly, reducing parental growth and survival and, thereby, compromising future reproductive success. To determine if an exotic benthic predator might be affecting parental care by nest-guarding smallmouth bass (Micropterus dolomieu), we compared nest-guarding behavior and energy expenditures in two systems, one with a hyperabundant recently introduced predator, the round goby (Neogobious melanostomus). In Lake Erie, USA, smallmouth bass vigorously defended their nests from benthic round gobies. In Lake Opeongo, Canada, smallmouth bass were exposed to fewer and predominantly open-water predators and were less active in their nest defense. From scuba and video observations, we documented that nest-guarding smallmouth bass chased predators (99% of which were round gobies) nine times more frequently in Lake Erie than in Lake Opeongo. This heightened activity resulted in a significant decline in weight and energetic content of guarding males in Lake Erie but no change in Lake Opeongo males. Bioenergetic simulations revealed that parental care increased smallmouth bass standard metabolic rate by 210% in Lake Erie but only by 28% in Lake Opeongo. As energy reserves declined and offspring became increasingly independent, males in both lakes consumed more prey and spent more time foraging away from their nests; however, nest-guarding smallmouth bass consumed few prey and, in Lake Erie, rarely consumed round gobies. Therefore, increased parental care costs owing to the presence of round gobies could affect future growth, reproduction, and survival if smallmouth bass approach critically low energy reserves. Copyright 2005.bioenergetics; exotic species; nest defense; parental care; round goby; smallmouth bass