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2000 Florida Mullet Stock Assessment

This article, a 2000 update of the status and trends and stock assessment of Florida mullet, Mugil cephalus, addresses commercial and recreational landings, fishing mortality, and additional statistics.

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Status and trends in the Florida mullet fishery and an updated stock assessment

Behzad Mahmoudi
Florida Fish and Wildlife Conservation Commission
Florida Marine Research Institute
St. Petersburg, FL
September 2000

EXECUTIVE SUMMARY

This report provides an update on the status of striped mullet stocks in Florida based on analyses of the most recent commercial and recreational statistics, fishery-independent monitoring, and biological data integrated into age-based assessment models. Total commercial and recreational landings of striped mullet in 1999 were about 10.6 million lbs. The commercial landings contributed about 89% of the total landings. The landings have gradually increased since the net limitation in 1995 when the total landings were 6.5 million lbs. The 1999 landings were still substantially lower by 58% than the pre-regulation level (an average of 25 million lbs for 1950–1994). The recent increases in commercial landings have occurred mostly in the southwest region (where over 60% of landings have been made historically) and during the roe season. The roe season landings in the southwest region increased from 1.4 million lbs in 1995/96 to 5.6 million lbs in 1999/00, equal to the levels of landings made during 1993/94 and 1994/95, prior to the net limitation. The statewide fishing effort has also increased since the net limitation, from 24,943 trips in 1995 to 29,264 trips in 1999. As with landings, most of this increase occurred in the southwest region during the roe season.

Results from our age-structured modeling show that the fishing mortality rates declined substantially during the post net-limitation period (1995–99) compared to the pre net-limitation period on the east and west coasts of Florida. In the southwest region, fishing mortality declined from 0.8–1.2 per year during 1991–1994 to 0.2–0.57 per year during 1995–1999. In 1999, fishing mortality was estimated at 0.42 per year (sex combined) and 0.47 per year (females) per year. The decline in fishing mortality has resulted in a significant increase in the stock size and the spawning stock biomass in recent years. Similar patterns of decline in fishing mortality and increase in stock size were shown for the northwest and southeast regions. The 1999 fishing mortality estimates in the range of 0.42–0.47 indicate that the Spawning Potential Ratio (SPR) has apparently reached the target level of 35% as was projected in our 1998-assessment report. Sensitivity analyses showed that there was a high probability associated with the 1999 mean fishing mortality and spawning stock size estimates. However, the 1999 SPR is a transitional estimate and marks the first year that the SPR has reached the target level.

Trends in relative abundance estimated from the fishery-independent and fishery-dependent monitoring data support the results from the age-structured modeling. The abundance of new recruits, pre-adults, and adults has increased in recent years. Median juvenile catch rates were significantly (p <0.05) higher in 1995, 1998, and 1999 in the southwest region and in 1996 and 1998 in the southeast region than in any other year during the 1989–1999 sampling period. Mean standardized commercial catch-per-unit-of-effort, which fluctuated during 1991–94, increased significantly between 1996 and 1999. The size/age distributions collected during 1993–1999 trammel-net surveys in the southwest region showed a substantial increase in the number of mullet 4 years and older following the net-limitation. In addition, there has been a gradual increase in the female proportion of the spawning population in recent years.

Significant changes have occurred in the mullet fishery and in the mullet population structure in the past few years and illustrate that the rebuilding of mullet stocks is occurring at a healthy rate. If mullet production stabilizes at the present level and recovery of mullet stocks continue at the same rate, fishing mortality should decline further. However, fishery statistics of recent years indicates that commercial landings and fishing trips have increased rapidly since 1995 (especially in the southwest region), and have not yet reached stable levels.

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For more information:

Stock Assessments: View other stock assessments for finfish and invertebrates.
Striped Mullet Species Account: Read the striped mullet species account.