Fish Habitat: Essential Fish Habitat and Rehabilitation

<em>Abstract</em> .—Defining and quantifying essential fish habitat is difficult, perhaps particularly so in estuaries, which are typically dynamic. Yet we need habitat data to make informed decisions about the management of estuarine habitats and associated fish populations. Our ongoing efforts to resolve issues of fish habitat quality have been centered in the relatively unaltered Jacques Cousteau National Estuarine Research Reserve (the Reserve) in the Mullica River–Great Bay estuary in southern New Jersey, where extensive studies of fishes and their habitats have been conducted during the last decade. Much of our effort to define essential fish habitat has focused on a variety of shallow-water habitats (eelgrass, macroalgae, marsh creeks, unvegetated substrates of different grain sizes) where it is easier to sample in a quantitative manner (e.g., using throw traps and beam trawls) and conduct experimental manipulations (e.g., caging, deploying of artificial habitats). Although our studies in the Reserve have been extensive, they still have been focused on a relatively small component (less than 3%) of the fish fauna of the Reserve, including several species of economic importance. These species include winter flounder <em>Pseudopleuronectes americanus</em> , summer flounder <em>Paralichthys dentatus</em> , tautog <em>Tautoga onitis</em> , and black sea bass <em>Centropristis striata</em> . This work has examined the period from larval ingress and settlement through the first year using a variety of complementary approaches. To date, these studies have included measures of habitat-specific distribution, abundance, residence time, and growth. Attempts to identify both habitat-specific measures of mortality and sources of mortality have proven especially difficult for the migratory fishes typical of Middle Atlantic Bight estuaries. In fact, this mobility, which occurs at seasonal, diel, tidal, and episodic (storms, upwelling, etc.) scales, makes it difficult to assess residence times and confounds attempts to measure habitat quality. The measures of habitat quality that we have used suggest that there are species-specific and habitat-specific responses; however, data sets for multiple years are seldom available to confirm these responses. Efforts to quantify essential fish habitat will be limited in their effectiveness until interannual variability can be assessed.