Modeling the impacts of bottom trawling and the subsequent recovery rates of sponges and corals in the Aleutian Islands, Alaska

The abundance of some marine fish species are correlated to the abundance of habitat-forming benthic organisms such as sponges and corals. A concern for fisheries management agencies is the recovery of these benthic invertebrates from removal or mortality from bottom trawling and other commercial fisheries activities. Using a logistic model, observations of available substrate and data from bottom trawl surveys of the Aleutian Islands, Alaska, we estimated recovery rates of sponges and corals following removal. The model predicted the observed sponge and coral catch in bottom trawl surveys relatively accurately ( R 2=0.38 and 0.46). For sponges, the results show that intrinsic growth rates were slow ( r=0.107 yr −1). Results show that intrinsic growth rates of corals were also slow ( r=0.062 yr −1). The best models for corals and sponges were models that did not include the impacts of commercial fishing removals. Subsequent recovery times for both taxa were also predicted to be slow. Mortality of 67% of the initial sponge biomass would recover to 80% of the original biomass after 20 years, while mortality of 67% of the coral biomass would recover to 80% of the original biomass after 34 years. The modeled recovery times were consistent with previous studies in estimating that recovery times were of the order of decades, however improved data from directed studies would no doubt improve parameter estimates and reduce the uncertainty in the model results. Given their role as a major ecosystem component and potential habitat for marine fish, damage and removal of sponges and corals must be considered when estimating the impacts of commercial bottom trawling on the seafloor. ► We estimated logistic population growth rates for sponges at r=0.107 yr −1 and corals r=0.062 yr −1. ► A mortality of 67% of sponge biomass would recover to 80% of the original biomass after 20 years. ► A mortality of 67% of coral biomass would recover to 80% of the original biomass after 34 years. ► Errors for the estimates were large, and could be improved with data from directed studies.