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 indicated that the model accurately estimated killifish growth. Predicted growth differed on average by only 14% from observed values. Field estimates of food consumption show that killifish can potentially double their daily food intake by adding marsh surface foods to their diet during each 2–3 h period of marsh access. Our model predicts that killifish grow from 20 to 44% faster if they add intertidal marsh surfaces to their subtidal feeding areas, 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°C, 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. Killifish that are spawned early (April) develop under thermal regimes and periods of marsh access that differ from those spawned late (September), leading to large differences in the mass that could be achieved by the next spawning season. At age 1 year, early-spawned (ES) fish are 35–50% larger than late-spawned fish. Bioenergetics model are useful for determining the value of vegetated areas for fish (an important mitigation issue), designing for coastal wetland restoration (e.g. inclusion of marshes), and maintaining salt marshes as important fish habitat in southern California.