Evaluation of nursery habitat: an ecophysiological approach

Abstract

DEL TORO SILVA, FELIX M.: Evaluation of nursery habitat: an ecophysiological approach.

Abiotic conditions can determine biomass production within habitats and this can influence the relative contribution of nursery habitats to adult populations, yet few studies have addressed how the interactions of abiotic parameters can influence production. Through a combination of laboratory experiments, simulation modeling, and field experiments the effects of abiotic dynamics on fish growth were examined. The objective of the study were to: (1) assess the effects of oxygen and temperature dynamics on growth; (2) test three indices of metabolic capacity (MMS, RMR, LOC) as indicators of fish performance relative to these dynamics; (3) develop a simulation model to predict growth based on abiotic conditions; (4) validate the model in four nursery areas within the Pamlico River Estuary; (5) compare habitat classification based on model results with juvenile abundance classification. Results showed significant individual and interaction effects of oxygen and temperature on growth. No significant abiotic effects on RMR were detected, but significant effects were detected for the other two indices (MMS and LOC). MMS indices showed a pattern similar to the observed growth rates in response to temperature and oxygen treatments. The model was successfully parameterized with laboratory data and validated through simulations of field trials. The model successfully reproduced growth rates in the field using environmental data (oxygen, temperature and salinity) as input variables and more importantly, it reproduced in a fine temporal scale dynamics of growth rate within the simulations. Comparisons of habitat classification between juvenile abundance and model simulations were not possible because environmental conditions during field experiments were so sever that most of the experiments resulted in negative growth rates. Overall, the study demonstrated the importance of abiotic dynamics on individual performance and resulting biomass production within a habitat and that the ecophysiological framework is an adequate model to develop and test hypothesis of mechanism affecting production within nursery habitats.