Fish Habitat: Essential Fish Habitat and Rehabilitation

Part Two: Essential Fish Habitat Identification

John A. Musick

doi: https://doi.org/10.47886/9781888569124.ch6

The fishes are the most diverse group of vertebrates on earth with some 24,000 species estimated. This great biodiversity is associated with great habitat diversity that comprises the aqueous biosphere from freshwater, to estuaries, to the coastal seas, to vast oceanic water masses.

Identification of essential fish habitat (EFH) among a multitude of environments requires a multitude of methods. In this section, five papers are presented that reflect the diversity of methods that might be employed to evaluate EFH for groups of fishes that depend on different habitats.

Thomas Minello studies habitat utilization by juvenile fishes and crustaceans in the highly productive estuaries of the northern Gulf of Mexico. Using drop nets in several different habitats, Minello analyzes animal density patterns within habitats to designate EFH. Minello concludes that all of the six habitat types he studied are likely to be essential for some fishery species. He stresses the need for additional, broader systematic sampling to define geographic differences in habitat utilization and also to examine intra-habitat variability. As a final note, Minello stresses that the identification of EFH requires an understanding of the functional relationships between species and habitat parameters.

David Packer and Tom Hoff review habitat utilization in the Middle Atlantic Bight by the summer flounder Paralichthys dentatus , one of the most important recreational and commercial fishes in that region. They begin with an extensive literature review of the critical habitat parameters for juvenile summer flounder. The authors have been able to glean information beyond simple preferred salinity and temperature ranges. Summer flounder has been well studied and thus information is available on the effects of temperature on growth and so forth. In addition to their literature review, Packer and Hoff analyze catch-per-uniteffort data from the National Marine Fisheries Service’s (NMFS’s) groundfish surveys and egg and larval surveys to provide seasonal density distribution maps over the continental shelf. In addition, they use presence–absence data from the National Oceanic and Atmospheric Administration’s (NOAA’s) Estuarine Living Marine Resources Program to map the utilization of estuaries by juvenile summer flounder. Packer and Hoff note that juvenile summer flounder are clearly estuarine dependent and thus estuaries should not only be identified as EFH but also as habitat areas of particular concern (HAPCs). Such HAPCs are critical to the sustained production of a species and are rare or sensitive to anthropogenic perturbations.

Anadromous fishes present problems in defining EFH different than those for marine and estuarine forms. Philip Roni and his colleagues make an important first attempt at defining EFH for four species of anadromous salmon Oncorhynchus spp. in the Pacific Northwest. For some of these species, EFH may include lotic spawning reaches $3,200 km from the ocean where they have sustained most of their growth. In addition, spawning and migration patterns may vary greatly among stocks, species, and drainages. The authors use geographic information system databases to define freshwater EFH for Pacific salmons, but they encountered difficulties with finer-scale resolution <1:100,000. The authors recommend that future efforts should focus on developing accurate seasonal salmon distribution data at a 1:24,000 scale.

Peter Rubec and his coauthors have developed habitat suitability index (HSI) models for spotted seatrout Cynoscion nebulosus for two estuaries on the west coast of Florida. Their results are encouraging in that models developed for Tampa Bay predicted fairly well the habitat suitability patterns for the same species measured in Charlotte Harbor. Thus, HSI models developed in one system may be useful in predicting HSI patterns in other nearby systems. Caution is advised in attempting to apply this paradigm to systems that are geographically more distant or where environmental differences among systems constrain the distribution of original environmental parameters used to develop the models. In addition, inter-area differences in biological communities (predators, competitors, etc.) may alter distribution patterns of species regardless of the environmental parameters.