How Many Mullet are there in Florida Bay?

Author： Scott Gerald P. Dewey Michael R. Hansen Larry J. Owen Ralph E. Rutherford Edward S.

Publisher： University of Miami - Rosenstiel School of Marine and Atmospheric Science

ISSN： 0007-4977

Source： Bulletin of Marine Science, Vol.44, Iss.1, 1989-01, pp. : 89-107

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Abstract

A fishery independent sampling survey design was implemented in the Everglades National Park's Florida Bay to estimate the monthly biomass of mullet (Mugil spp.) in the area. The method was an application of aerial visual sampling, photogrammetric sampling, and shipboard sea-truth sampling. Aerial visual sampling was used to estimate the density (D_M) and number of “muds” in the study area. Photogrammetric sampling was used to estimate mud surface area, and shipboard sampling was used to estimate the proportion of muds containing mullet and the biomass of mullet per unit area of mud (b). Total biomass was estimated as the product of these four variables. The method applied proved to be appropriate for silver mullet. Biomass of silver mullet estimates were found to be characterized by a high degree of variation (CY ≅ 35%), owing primarily to variability of estimates of b and D_M Mud density estimates were found to be a relatively precise (CY ≅ 20%) index of presumed mullet abundance based on comparison with fishery CPUE data. Bias was estimated to result in underestimation of mullet biomass on the order of a factor of 9.6 to more than 19.0. The major source of bias was due to estimates of b. Estimated monthly harvest of silver mullet in April-December 1984 ranged from 2.4 to 12.0% of the bias-adjusted estimates of biomass.