Effect of Caribbean Spiny Lobster Traps on Seagrass Beds of the Florida Keys National Marine Sanctuary: Damage Assessment and Evaluation of Recovery

In the Florida Keys, traps for spiny lobsters (also known as Caribbean spiny lobster) Panulirus argus are often deployed in seagrass beds. Given that several hundred thousand traps may be deployed in one fishing season, the possibility exists for significant impacts to seagrass resources. The question was whether standard fishing practices observed in the fishery actually resulted in injmies to seagrass. This study was designed to measure the degree of injury to seagrass as a function of trap deployment duration (soak time) and habitat type (seagrass species) and the recovery of seagrass following trap removal. Aspects of the deployment and retrieval process were not examined. Sampling grids composed of 30 3-m x 3-m squares were arbitrarily established within each of three monospecific seagrassbeds (two of Thalassia testudinum and one of Syringodium filiforme) near Marathon, Florida. Five squares within each grid remained trap-free (controls) while the remaining squares each received a single trap. Five traps from each grid were randomly removed at each of five soak times (ranging from 1 to 24 weeks). Immediately before deployment and following trap removal, seagrass short shoot densities were recorded and compared among controls and treatments. Both seagrass species exhibited significantly decreased shoot densities after 6-week and 24-week soak times. Thalassia testudinum densities within the 6-week and 24-week treatments had returned to control densities 4 months after trap removal, while densities of S. filiforme remained significantly decreased at the end of 24 weeks. We conclude that traps must be recovered within a 6-week period, beyond which injury to seagrass beds is predicted, with long lasting effects to beds of S. filifonne. Within the limits of these testing parameters, it appears that standard fishing practices (typically < 5-week soak time) should not result in a significant injury to seagrass beds in the Florida Keys.