Influence of flood frequency, temperature and population density on migration of Fundulus heteroclitus in semi-isolated marsh pond habitats

摘要

Fish respond to habitat and demographic factors that affect growth and survival through migration, reproduction and mortality. However, the importance of migration rates on fish population dynamics and the effects of habitat and demographic factors on movement are not well understood. We used mark-recapture to determine population dynamics (recruitment, mortality, immigration and emigration) of the mummichog Fundulus heteroclitus inhabiting semi-isolated ponds in a New Jersey salt marsh over the spring and summer of 2002. We tested the effects of marsh pond flood frequency, water temperature and fish density on mummichog emigration from marsh ponds. Results show that during the April to July study period, monthly emigration rates averaged 30 % and tended to decline from spring to summer in most ponds. Recruitment and immigration were negligible after May and June, respectively. Increasing mortality and decreasing emigration and immigration over the study period suggested that there was a shift in the importance of movement in regulating mummichog population size in marsh ponds. The mean rate of emigration showed a significant negative relationship with the frequency of flooding in a pond. Neither mummichog density nor water temperature was strongly correlated with emigration rate. Our finding of lower emigration from ponds with higher flooding frequency suggests that frequent pond flooding indirectly triggers stationary behaviour in mummichogs because of enhanced water quality and food abundance.