Estuarine-Dependent Fish
Habitat Linkages and Estuarine-Dependent Fish
The over-whelming majority of economically important species in the Gulf of Mexico are estuarine dependent during one or more stages in their life history. Different estuarine-dependent species have different reproductive strategies, occupy the estuary during different life history stages, and have varying lengths of stay, timing of recruitment, and essential habitats. Many species (e.g., spotted seatrout, Cynoscion nebulosus; common snook, Centropomus undecimalis) typically complete their entire life history within the estuarine environment. Other species reproduce in the Gulf of Mexico but use estuarine environments for the first 12 – 18 months (e.g., gag, Mycteroperca microlepis; gray snapper, Lutjanus griseus), first several years (e.g., red drum, Sciaenops ocellatus; goliath grouper, Epinephelus itajara), or majority of their life history (e.g., striped mullet, Mugil cephalus). These estuarine-dependent species use the many, varied habitats available within an estuary. Common snook, for instance, are typically most abundant in backwater areas during their first year but move into and in-between many other habitats (e.g., rivers, seagrasses, fringing mangroves, open beaches, passes, manmade structures) during various life history stages and ecological seasons. Recruitment to, and movement between these various estuarine habitats can be restricted by barriers. The most obvious barriers within estuaries are physical structures (e.g., dams, weirs, causeways) but less obvious, non-structural barriers also exist (e.g., freshwater inflow, dissolved oxygen). Habitat degradation within an estuary (e.g., dredge and fill, mangrove trimming, hardened shorelines) and within the estuary’s watershed (e.g., impervious surfaces, stormwater runoff) can also limit movement and recruitment. The life history strategies of several estuarine-dependent species, their habitat linkages, impediments to their successful recruitment and the data available to assess recruitment success during various life history stages will be discussed.
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Submitted by: Timothy C. MacDonald, Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute