they approach maturity, blue crabs seek lower salini- 

 ties. Life stages considered in this report are adults, 

 mating (instead of spawning), juveniles, larvae, and 

 eggs. 



• Stone aabs: Usually found in salinities greater than 

 20 ppt. Males are typically in nearshore waters, but 

 migrate into the estuaries for mating. Life stages 

 considered in this report are adults, mating, juveniles, 

 lan/ae, and eggs. Williams and Felder (1986) have 

 distinguished two separate species in the Gulf of Mexico. 

 The stone crab (Menippe mercenaria) occurs from 

 Florida Bay to Apalachicola Bay, and the Gulf stone 

 crab (M. adina) is found from Suwannee River to the 

 Yucatan peninsula. M. mercenaria is also known as 

 Florida stone crab (Williams et al. 1989). 



Fishes. Aggregating species by salinity zone uses a 

 single fundamental habitat parameter. However, a 

 combination of habitat characteristics, such as bottom 

 type, water temperature, and bathymetry, would more 

 accurately indicate species' spatial and temporal distri- 

 butions. Specific habitat requirements and life history 

 characteristics of a number of fishes are presented 

 here: 



• Bull shark: Development of eggs and larvae are 

 internal, and parturition results in pups of juvenile size 

 (75 cm TL). Therefore, only juveniles and adults are 

 found in the estuaries. Fishing gear usually limits the 

 ability to take large sharks. Based on the sizes of 

 sharks captured, it may be inferred that parturition is 

 occurring within the estuaries. Life stages considered 

 in this report are adults, mating, juveniles, and parturi- 

 tion. 



• Tarpon: Spawning, egg, and larval stages occur well 

 off shore. Juveniles use the estuaries as a nursery 

 ground, often seeking waters of low dissolved oxygen 

 and low salinity. 



• Alabama shad: Not found west of the Barataria Bay 

 barrier islands in Louisiana, nor in south Florida. 



• Menhaden: Juveniles are the predominant life stage 

 utilizing the estuaries. Spawning generally occurs 

 from the coastline to six miles offshore. Gulf menha- 

 den (Brevoortia patronus) are generally not common 

 south of Tampa Bay, and yellowfin menhaden 

 {Brevoortia smithi} are generally not common north 

 and west of Tampa Bay. The two species may hybrid- 

 ize where their ranges overlap. 



• Gizzard shad: Large juveniles and adults are found 

 in estuaries, but adults must return to freshwater to 

 spawn. In large rivers there is an upstream migration 

 or "spring run." Juveniles that are washed into bays 



with floods can mature to adulthood, but their upstream 

 migration may be impeded by dams, weirs, and other 

 waterway restrictions. Not common in south Florida 

 estuaries. 



• Bay anchovy: All life stages occur in estuaries, 

 although adults may move offshore. This is a key 

 forage species that is one of the most abundant fishes 

 in Gulf of Mexico estuarine waters. 



• Hardhead catfish: Eggs and lan/ae are brooded in 

 the mouths of adult males; therefore, their distribution 

 is determined by the adult population. 



• Sheepshead minnow: The entire life cycle is com- 

 pleted within the estuary, and all life stages are euryha- 

 line and eurythermal. This species tends to prefer 

 open bottom to heavily vegetated areas. 



• Gulfkillifish: All life stages are estuarine, euryhaline, 

 and eurythermal. This species occurs in shallow 

 estuarine waters, including mangrove and flooded 

 marsh habitat. 



• Silversides: Two species commonly occur in Gulf of 

 Mexico estuaries: the tidewater silverside, Menidia 

 pen/nsL//ae, and inland silverside,yif.t)e/y///na(Chernoff 

 etal. 1981, Robins etal. 1991). The two were fomnerly 

 considered to be a single species (Robins et al. 1980). 

 Although they do occur together and occasionally 

 hybridize, the tidewater silverside is generally found in 

 moderate to high salinity estuarine waters, and the 

 inland silverside in low salinity estuarine waters and 

 inland freshwater (Johnson 1975). These species are 

 considered together in this report because most fisher- 

 ies data do not distinguish between them. All life 

 stages are estuarine, euryhaline, and eurythermal. 

 Adults and juveniles form schools, primarily in shallow 

 waters near the surface, and are often abundant. 



• Snook: Also known as common snook (Robins etal. 

 1991). The snook is most common in the southern 

 Florida estuaries, but also occurs in Texas. Adults and 

 juveniles are euryhaline, but are quite sensitive to cold 

 temperatures. 



• Bluefish: Spawning, egg and larval development 

 occur offshore. Juveniles and adults are the principal 

 life stages found in estuaries. The bluefish is a prima- 

 rily visual predator, and often schools. In the Gulf of 

 Mexico, they are generally most common from Missis- 

 sippi Sound eastward. 



• Blue njnner and crevalle jack: Juveniles and adults 

 enter estuaries, but other life stages are usually off- 

 shore. 



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