The importance of marsh access to growth of the California killifish, Fundulus parvipinnis, evaluated through bioenergetics modeling

We developed, tested, and applied a bioenergetics model for the California killifish, fundulus parvipinnis, to estimate the benefits of vegetated salt marsh habitats to killifish growth. Three independent statistical tests in dicated that the model accurately estimated killifish growth. Predicted gro wth differed on average by only 14% from observed values. Field estimates o f food consumption show that killifish can potentially double their daily f ood intake by adding marsh surface foods to their diet during each 2-3 h pe riod of marsh access. Our model predicts that killifish grow from 20 to 44% faster if they add intertidal marsh surfaces to their subtidal feeding are as, despite higher metabolic costs and lower food assimilation during marsh feeding. Killifish may potentially grow up to 100% faster if energy costs associated with marsh access are minimized. During March-May, daytime tides are not high enough to permit marsh access. At water temperatures above 20 degreesC, growth of adult killifish ( > 3.5 g wet mass, > 60-62 mm, TL) is more adversely affected than that of juveniles by lack of marsh access. Ki llifish that are spawned early (April) develop under thermal regimes and pe riods of marsh access that differ from those spawned late (September), lead ing to large differences in the mass that could be achieved by the next spa wning season. At age 1 year, early-spawned (ES) fish are 35-50% larger than late-spawned fish. Bioenergetics model are useful for determining the valu e of vegetated areas for fish tan important mitigation issue), designing fo r coastal wetland restoration (e.g. inclusion of marshes), and maintaining salt marshes as important fish habitat in southern California. (C) 2001 Els evier Science B.V, All rights reserved.