West Florida

Background information

On June 19, 2000, the Gulf of Mexico Fishery Management Council created two Marine Protected Areas (MPAs) located between 28 and 30 degrees latitude in the northeastern Gulf of Mexico. These MPAs, Madison-Swanson and Steamboat Lumps, were closed to all fishing in an effort to increase the stock size of gag grouper in the northern Gulf. This action was taken in response to a 1997 gag grouper stock assessment and a recommendation from the Reef Fish Stock Assessment Panel suggesting gag grouper, while not overfished, may be undergoing overfishing. In 2000, the total fishing ban was relaxed to allow fishing for highly migratory species (tunas, swordfish, oceanic sharks, and billfishes). The life history strategy for gag makes them particularly vulnerable to fishing during their spawning season. Gag are protogynous hermaphrodites, that is, all gag are born as females and a small percentage switch sex to males once they reach a certain size and if no other males are nearby. During the spawning season, December - April, female gag gather in large breeding harems of up to 50 fish, all guarded by a single male. This male becomes very territorial and loses his natural wariness of baited hooks. The practice of fishing on gag spawning aggregations increases the focus of the fishery on large breeders, decreases the proportion of males in the population, disrupts the social structure of the spawning groups, and can even cause complete loss of spawning groups. Therefore, it was recommended that a representative area of known gag spawning habitat be closed to fishing. To evaluate the effectiveness of the marine reserve concept in this application, the Madison-Swanson and Steamboat Lumps areas were chosen as study sites. Both are approximately the same size (roughly 100 square miles), contain similar depths (200-400 ft.), and have similar habitat (rocky ledges on sandy plains). The differences are the geographic locations and the scale of the rocky habitat, Madison-Swanson is characterized as high relief and Steamboat Lumps is characterized as low relief. Another area of similar depth and habitat, called the Twin Ridges is adjacent to Madison-Swanson and will be studied as a control site because it remains open to fishing.

Objectives

• Baseline estimates of fish abundances
• Age structure and reproductive status of groupers and snappers
• Describe habitat features
• Locate spawning aggregations of groupers and snappers
• Compare selectivity of fish hooks with Chevron traps and video gear