Ecosystem- and Taxon-specific Dynamic and Energetics Properties of Larval Fish Assemblages
Abstract:Growth rates, mortality rates, and energetics properties of teleost larvae differ among species and among ecosystems. In this synthesis, the ingestion rates required to support mean growth of larvae were estimated and energy budgets were developed. Weight-specific growth coefficients (G), instantaneous mortality rates (Z), larval stage durations (D), gross growth efficiencies (K1), and weight-specific oxygen uptake (QO2) were obtained from published sources and categorized by marine and freshwater species. Rates and properties were subcategorized by marine ecosystems and by taxonomic group. The strong temperature dependencies of rates and properties for larvae were adjusted by analysis of covariance to allow mean values to be compared among ecosystems and taxa. After adjustment, relatively few significant differences were detected, indicating that, with important exceptions, teleost larvae have characteristic and predictable attributes. Marine fish larvae have higher Z, longer D and higher QO2 than freshwater larvae, probably because marine larvae weigh less at hatch (47 μg versus 339 μg). Larvae of coral reef fishes had lower temperature-adjusted G than larvae from other marine ecosystems. Values of K1 (mean = 0.301) differed little among ecosystems or taxonomic groups and were not related to temperature. Energy budgets, which integrate the effects of rates and properties, differed appreciably among ecosystems and taxa. Ingestion, metabolism, and assimilation were higher for marine than for freshwater larvae. Mean temperature-adjusted ingestion rates usually were 40 to 65% of body weight, although values as high as 97% (Scombroidei) were estimated. Larvae from cool ecosystems (10°C) required two to four times less ingested energy on a daily basis than larvae from warm systems (28°C) to grow at their respective mean rates. Assimilation efficiencies declined as temperature increased. Temperature-adjusted mean assimilation efficiencies (Ā) were 0.65 for marine and 0.56 for freshwater teleost larvae; Ā ranged from 0.54 (shelf) to 0.75 (upwelling) for marine ecosystems, and from 0.47 (Salmoniformes) to 0.82 (Gadiformes) across taxonomic groups. Rates and relationships reported here, while not intended to predict species-specific responses, do provide information on deviations by individual species from predicted rates and can identify specific adaptations and life-history strategies. Results of the analyses will be useful to categorize, compare, and model ichthyoplankton assemblages in pelagic communities.
Document Type: Research Article
Publication date: September 1, 1993
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