Comparative Growth, Mortality, and Energetics of Marine Fish Larvae: Temperature and Implied Latitudinal Effects

Vital rates and energetics of marine fish larvae were examined in relation to temperature to determine if recruitment potential and spawning strategies might vary as a consequence of differences in these traits among species. Literature-derived values of growth rates, mortality rates. larval stage durations, gross growth efficiencies, and oxygen uptakes were considered. Results were presumed to reflect latitudinal variation among species. Instantaneous daily growth and mortality rates each increased approximately 0.01 per °C increase in temperature. But. there was no significant regression of gross growth efficiency on temperature (mean K) = 0.29), indicating no latitudinal relationship. The large increases in growth rate at high temperatures must be supported by increased food consumption, not increased growth efficiency. Oxygen uptakes also increased significantly in relation to temperature. but relatively slowly compared to growth rates. Larval stage duration was inversely related to growth rate. The potential variability in growth rate was observed to increase with temperature, but the opposite trend was observed for stage duration. Thus. stage durations tended to be both long and potentially variable in high latitudes. Because of these characteristics it is suggested that early life. density-dependent regulation is more probable in high than in low latitudes. The required ingestion to support average growth rate increased threefold in the 10°_ 30°C range. indicating that fish larvae in warm seas may be more likely to starve than larvae in cold seas. Spawning in low latitudes often is protracted with frequent batches in contrast to spawning in high latitudes. where seasons are brief. with one or a few batches. The different strategies may have been selected and maintained to counter energetic and dynamic constraints in the larval stage. Variability in growth and mortality rates of marine fish larvae can cause fluctuations in recruitment levels. The two processes, growth and death, may interact and can be viewed as a Edward D. Houde. University of Maryland System: Center for Environmental and Estuarine Studies, Chesapeake Biological Laboratory, Solomons. MD 20688. Manuscript accepted March 1989. Fishery Bulletin, U.S. 87:471-495. "single process" in early life (Cushing 1975). In reviewing larval mortality rates, it is apparent that not only are rates high but they range widely (Dahlberg 1979; McGurk 1986). Growth rates also are valiable, both among and within species, which could cause significant fluctuations in recruitment levels through effects on larval stage duration (Houde 1987). If variation in the magnitude of larval growth or mOltality were predictable, for example, in relation to latitude, the consequences of it might be discernible in life history strategies or in physiological adaptations of fishes from different temperature zones. Objectives of this paper are to compare vital rates and energetics parameters of marine fish larvae, and to discuss results in the context of spawning strategies and possible mechanisms in the larval stage that may regulate the recmitment process. A cursory examination of literature indicated that teleost larval growth and mortality rates increased relative to temperature and that temperature could, in a general way, be equated to latitude. A review and comparative analysis were undertaken to define the relationships between temperature alld the larvae 1) growth rates. 2) stage duration, 3) mortality rates, 4) growth efficiency, and 5) oxygen uptakes. From the analysis, it was possible to estimate cohort net survivorships. to develop energy budgets, and to estimate ingestion requirements of first-feeding larvae over the range of temperatures that was surveyed. The likelihood of starvation by marine fish lal'vae from low and high latitudes was considered. Because spawning strategies of marine fishes may be linked to larval dynamics and energetics, results also were considered in relation to dominant spawning patterns in warm and cold seas.