• Bay scallop: Usually associated with seagrass 

 beds and salinities greater than 25 ppt. 



• Rangia: All life stages occur in salinities below 

 25 ppt. 



• Hard clam: Most life stages occur in salinities 

 above 20 ppt. 



• Bay squid: The lower lethal salinity limit is 1 7.5 

 ppt, and bay squid actively avoid salinities that 

 are lowerthan this. Therefore, thedistribution of 

 juveniles and adults will only be from the lower 

 margin of the mixing zone to the seawater zone, 

 and out to the nearshore shelf waters of the Gulf 

 of Mexico. 



• Penaeid shrimp: Postlarvae and juveniles are 

 the critical life stages utilizing the estuaries. 

 Adults generally move to nearshore spawning 

 grounds, where spawning, egg development, 

 and most of the larval development occur. 



• Grass shrimp: Fertilized eggs are held on the 

 female's pleopods until hatching. 



• Spiny lobster. Spiny lobsters are found in the 

 Gulf of Mexico estuaries of southern Florida and 

 southern Texas. Juveniles do not mature to 

 adult stages until 6-8 years of age. 



• Stone crabs: Usually found in salinities greater 

 than 20 ppt. Males are typically located in 

 nearshore waters, but migrate into the estuaries 

 for mating. Williams and Felder (1986) have 

 distinguished two separtate species in the Gulf 

 of Mexico. The Florida stone crab, Menippe 

 mercenaria, occurs from Florida Bay to 

 Appalachicola Bay, and the Gulf stone crab, M. 

 adina is found from Suwannee River to the 

 Yucatan Penisula. M. mercenaria'is not included 

 in this report because it does not occur in the 

 Central Gulf of Mexico estuaries. 



• Bluecrab: Mating usually takes place in the low 

 salinities of the tidal fresh to the upper region of 

 the mixing zone. After mating, females move to 

 the seawater zone, while males often remain in 

 the upper reaches of the estuary. Females 

 brood the eggs (sponge females), and larvae are 

 released in higher salinities. Development 

 through the late zoeal stages occurs offshore. 

 Megalopae are transported back into the estuary 

 and disperse throughout the salinity zones. As 

 they approach maturity, blue crabs seek lower 

 salinities. 



Fishes. Aggregating species by salinity zone uses a 

 fundamental habitat parameter. However, a 

 combination of habitat characteristics, such as bottom 

 type, water temperature, and bathymetry, would 

 nrore accurately indicate species spatial and temporal 

 distributions. 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 (> 2220 cm TL) 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. 



• 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. 



• Menhaden: Juveniles are the predominant life 

 stage utilizing the estuaries. Spawning occurs 

 from the coastline to six miles offshore. Gulf and 

 yellowfin menhaden may hybridize where their 

 ranges overlap. 



• Gizzard shad: Large juveniles and adults are 

 found in the estuaries, but adults must return to 

 freshwater to spawn. In large rivers there is a 

 migration or "spring ain" up the river. Large 

 juveniles that are washed into bays with floods 

 can mature to adulthood, but their upstream 

 migration may be impeded by waterway 

 restrictions. 



• Hardhead catfish: Eggs and larvae are brooded 

 in the mouths of adult males; therefore, their 

 distribution is determined by the adult population. 



• Bluefish: Juveniles and adults are the principal 

 life stages found in estuaries. Adults may ascend 

 rivers into brackish waters. Spawning and 

 development of eggs and larvae occur offshore. 



• Crevalle jack and blue runner. Juvenile and 

 adult stages occur in estuaries, but other life 

 stages are usually offshore. 



• Florida pompano: Typically found in nearshore 

 surf and inlet waters, but juveniles and adults do 

 enterthe bays. Spawning, eggs, and larvae are 



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