Research Interests

My research interests involve the ecology and evolutionary biology of fishes and fisheries science. I seek to understand the adaptive significance of reproductive, behavioral, physiological, or life history traits in fishes and to extend this knowledge to fundamental problems in resource management. Species currently under investigation include the Atlantic silverside (Menidia menidia), the bluefish (Pomatomus saltatrix), and the striped bass (Morone saxatilis).

A long-standing interest of mine is to understand how the sex ratio evolves. I have been the first to show that sex determination in fishes is influenced by temperature during larval development. Most of this work has involved the Atlantic silverside but the phenomenon is now known to be widespread. These findings are important not only in designing approaches to sex ratio manipulation in aquaculture, but also to understanding the causes of fluctuations in sex ratio among natural populations.

Another long term interest concerns the population dynamics of bluefish. Each spring and summer, numerous young bluefish recruit to estuaries along the U.S. East Coast. Bluefish are unusual among east coast fishes in having a bimodal spawning and recruitment strategy. The reasons for this bimodal recruitment and its consequences are a major focus of our research. Bluefish are also unique with respect to the very large size attained by the end of their 1st growing season. My students and I have demonstrated that bluefish reach such large size by acquiring a predatory size advantage over their principal prey. This size advantage is a result of being spawned near the edge of the Gulfstream in the South Atlantic Bight early in the spring, northward advection, and invasion estuaries of the Middle Atlantic Bight at an advanced size, just as the growing season of the inshore prey fishes is beginning. The level of predation by juvenile bluefish determines the recruitment success of their principal prey such as striped bass in the Hudson River.

Another area of investigation concerns how growth rate is adapted to differences in seasonality that occur with latitude. In several species distributed along the east coast of North America, the length of the growing season declines with increasing latitude by a factor of about three. Yet body size at the end of the growing season is independent of latitude. Experimental studies on laboratory-reared fish explain this paradox: high-latitude fish have a higher genetic capacity for growth and grow two to three times faster within the growing season than do low-latitude fish. This "countergradient variation" in growth rate appears to be widespread and may provide a general model for choosing natural stocks to be used in aquaculture: natural populations with the highest capacity for growth may be found where the growing season is shortest. Rapid growth in the north evolves because size-dependent winter mortality affects small fish more severely than larger fish. The causes of winter mortality are yet another area of research in our lab. The existence of genetic variation in growth also implies that there must be evolutionary trade-offs that select for different growth rates at different latitudes. Much of our current research is directed at establishing the selective pressures that cause variation in growth rate.

Finally, I am very interested in the long term consequences of harvesting as a selective force that alters the evolution of life history traits in fishes. Because most fisheries selectively harvest the largest and fastest growing members of a population, the long term evolutionary response is likely to be slower individual growth and lower population productivity. We are currently conducting empirical simulation experiments, where captive populations of silversides are selectively harvested in different directions, to assess the rate at which life history characters might evolve under size-selective harvest in the wild.

For more information about my research, please visit the Conover Fish Ecology Lab website at http://www.msrc.sunysb.edu/~conover or click on the link above.

Selected Recent Publications

Munch, S.B., M. Walsh, and D.O. Conover. 2005. Harvest selection, genetic correlations, and evolutionary changes in recruitment: one less thing to worry about? Can. J. Fish. Aquat. Sci. 62 (4): 802-810.

Conover, D. O., S.A. Arnott, M.R. Walsh, and S.B. Munch. 2005. Darwinian fishery science: lessons from the Atlantic silverside. Can. J. Fish. Aquat. Sci. 62 (4): 730-737.

Hurst, T.P. , K.A. McKown, and D.O. Conover. 2004. Interannual and long term variation in the near-shore fish community of the mesohaline Hudson River estuary. Estuaries 27(4):659-669.

E. K. Pikitch, C. Santora, .E. A. Babcock, A. Bakun, R. Bonfil, D.O. Conover, P. Dayton, P. Doukakis, D. Fluharty, B. Heneman, E. D. Houde, J. Link, P. A. Livingston, M. Mangel, M. K. Mcallister, J. Pope, K. J. Sainsbury. 2004. Ecosystem-based fishery management. Science 305 (5682): 346-347

Conover, D.O. 2004. Temperature-dependent sex determination in fishes. pp. 11-20 In Temperature-dependent sex determination. N. Valenzuela and V. Lance (eds). Smithsonian Institution Press. (194 p).

Munch S.B. and D.O. Conover. 2004. Nonlinear growth cost in Menidia menidia: Theory and empirical evidence. Evolution 58 (3): 661-664.

Hurst, T.P. and D.O. Conover. 2003. Seasonal and interannual variation in the allometry of energy allocation in juvenile striped bass. Ecology 84: 3360-3369.

Conover, D.O., T. Gilmore, and S. B. Munch. 2003. Estimating the relative contribution of spring and summer-spawned cohorts to the Atlantic coast bluefish stock. Trans. Amer. Fish. Soc. 132 (6): 1117-1124.

Munch, S.B. and D.O. Conover. 2003. Rapid growth results in increased susceptibility to predation in Menidia menidia. Evolution 57 (9): 2119-2127

Munch, S.B., M. Mangel, and D.O. Conover. 2003. Quantifying natural selection on body size from field data with an application to winter mortality in Menidia menidia. Ecology 84(8): 2168-2177.

Conover, D.O. and S.B. Munch. 2002. Sustaining fisheries yields over evolutionary time scales. Science 297 (5578): 94-96.