2002 Florida Silver Mullet Stock Assessment

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Florida silver mullet fishery and stock assessment

Behzad Mahmoudi
Florida Fish and Wildlife Conservation Commission
Florida Marine Research Institute
St. Petersburg, FL
May 23 2002

EXECUTIVE SUMMARY

Three species enter the silver mullet fishery in Florida; white mullet (Mugil curema), redeye mullet (M. gaimardianus), and fantail mullet (M. gyrans). White mullet, being most common, are popular baitfish in the sport fishery and are commercially exploited along the Atlantic and Gulf coasts of Florida. The silver-mullet complex is utilized as trolling, live, strip, chunk, or cut fishing bait.

The Atlantic coast commercial landings of silver mullet averaged about 228,686 pounds per year during 1982-1995 and have doubled to an average of 451,755 pounds per year since 1996. Recent increase in the Atlantic coast landings reflected the rapid increase in the number of commercial fishing trips. The Gulf coast annual landings showed an opposite trend. Landings declined from an average of 407,304 pounds per year during 1982-1995 to an average of 118,740 per year during 1996-2000. Recreational landings (1982-2000) varied significantly from year to year on both coasts. From 1996 to 2000, the annual recreational harvests have averaged about 744,604 fish (approximately 148,921 lbs.) on the Atlantic coast and 221,796 fish (approximately 73,193 lbs.) on the Gulf coast.

Data were insufficient to develop an age-structured model for stock assessment of silver mullet in Florida. We chose methods, such as a modified De Lury and surplus production that use fisheries landings and effort time series, to generate estimates of population size and fishing mortality rates. According to our preliminary assessment, it appears that fishing mortality rate (F) has substantially increased on the Atlantic coast while it has declined on the Gulf coast in recent years. On the Atlantic coast, the F increased from an average of 0.20 per year during 1982-1995 to an average of 0.50 during 1996-2000. Despite recent increases in fishing mortality, it does not appear that the stock is overfished at present time. The current F estimate (F 2000 = 0.55 per year) was in the range of natural mortality estimates (0.4-0.64 per year) and was below the FMSY estimate of 0.64 per year. Recent increases in F, however, may have caused a decline in population biomass and the B current / BMSY ratio. Opposite trends have occurred on the Gulf coast. The F decreased sharply from an average of 0.14 per year during 1982-1995 to an average of 0.09 per year during 1996-2000. The current F estimate (F 2000 = 0.09 per year) was substantially below the FMSY.

Recent increase in landings on the Atlantic coast and potential for future increase of fishing effort is alarming. The current F could quickly reach or exceed the FMSY level if fishing effort continue to increase at the rate seen during 1994-1997 period. At present time, however, it appears that landing and fishing effort has somewhat stabilized on the Atlantic coast. The Gulf coast silver mullet population appears to be healthy. Assessment indicates no sign of either growth and or recruitment overfishing in this fishery.

Prior to July 1, 2004, the Fish and Wildlife Research Institute was known as the Florida Marine Research Institute. The institute name has not been changed in historical articles and articles that directly reference work done by the Florida Marine Research Institute.