Movements and Mortality Rates of Striped Mullet in North Carolina

Abstract

Striped mullet Mugil cephalus is an economically important species to commercial and recreational fishermen, as well as an ecologically significant detritivore linking lower trophic levels with a wide variety of estuarine and marine fish and birds. Despite this importance, striped mullet migration patterns and mortality rates are poorly understood. Approximately 15,000 striped mullet were tagged in North Carolina between 1997 and 2001, and monthly movement information was collected on recovered individuals (n = 384) from commercial and recreational fishermen and state agency personnel. A tag return model was used to estimate an instantaneous total mortality rate, and this rate was partitioned into natural and fishing components by means of life history methods. Nearly all (98.2%) striped mullet were recovered in North Carolina, the remaining few being recovered in nearby states. Striped mullet moved southward of their tagging locations and had the highest daily movement rate between the months of August and November. Movements corresponded to the months when spawning migrations are thought to occur in North Carolina. A smaller but substantial proportion of fish were recovered north of their tagging locations in late fall. Instantaneous total mortality rates of 2.12 and 1.71 were estimated using the two most parsimonious models for individuals larger than 300 mm fork length, comparing well with preliminary estimates from an independent statistical catch-at-age model. Concomitant holding tank experiments suggested that tag retention and posttagging survival, two central assumptions of the tag return model, were extremely high for adult striped mullet. These results will be incorporated into the North Carolina striped mullet fishery management plan currently in development.