Comparative Growth, Mortality, and Energetics of 



Marine Fish Larvae: Temperature and Implied 



Latitudinal Effects 



Edward D. Houde 



ABSTRACT: Vital rates and energetics of marine 

 fish larvae were examined in relation to tempera- 

 ture to determine if recruitment potential and 

 spawning strategies might vary as a consequence of 

 differences in these traits among species. Litera- 

 ture-derived values of growth rates, mortality 

 rates, larval stage durations, gross growth efficien- 

 cies, 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 A'l = 0.29), indicating no lati- 

 tudinal 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 signifi- 

 cantly 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 dura- 

 tions tended to be both long and potentially vari- 

 able in high latitudes. Because of these characteris- 

 tics it is suggested that early life, density-depen- 

 dent 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 gi-owth and mortality rates of ma- 

 rine fish larvae can cause fluctuations in recruit- 

 ment 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 Bio- 

 logical Laboratory, Solomons, MD 20688. 



Manuscript accepted March 1989. 

 Fishery Bulletin, U.S. 87:471^95. 



"single process" in early life (Gushing 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 variable, both among and within 

 species, which could cause significant fluctua- 

 tions in recruitment levels through effects on 

 larval stage duration (Houde 1987). If variation 

 in the magnitude of larval growth or mortality 

 were predictable, for example, in relation to lati- 

 tude, the consequences of it might be discernible 

 in life history strategies or in physiological adap- 

 tations 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 conte.xt of 

 spawning strategies and possible mechanisms in 

 the larval stage that may regulate the recruit- 

 ment process. A cursory examination of litera- 

 ture indicated that teleost larval gi'owth and 

 mortality rates increased relative to tempera- 

 ture and that temperature could, in a general 

 way, be equated to latitude. A review and com- 

 parative analysis were undertaken to define the 

 relationships between temperature and the lar- 

 vae 1) growth rates, 2) stage duration, 3) mortal- 

 ity rates, 4) gi-owth efficiency, and 5) oxygen 

 uptakes. From the analysis, it was possible to 

 estimate cohort net survivorships, to develop 

 energy budgets, and to estimate ingestion re- 

 quirements of first-feeding larvae over the range 

 of temperatures that was surveyed. The likeh- 

 hood of starvation by marine fish larvae from low 

 and high latitudes was considered. Because 

 spawning strategies of marine fishes may be 

 Unked to larval dynamics and energetics, results 

 also were considered in relation to dominant 

 spawning patterns in warm and cold seas. 



METHODS 



Literature was reviewed to obtain data for the 

 analyses. Relationships and variables that were 



471 



