Assessment of depredation by bottlenose dolphins in the Northwest Florida and Alabama sport fishery
By Steve Shippee, PhD Candidate, University of Central Florida
During 2008, we initiated a new study to assess the problem of harmful interactions between bottlenose dolphins and the sport fishery along the Northwest Florida – Alabama Gulf Coast. Sport anglers and boat operators report increasing incidences of dolphins stealing hook-and-line caught fish, regulatory discards, and bait. Aside from anecdotal information, little else is known about the extent and frequency of this problem, or of the consequence to dolphins that are injured or killed by fishing gear and the retributions of upset anglers. It is also unknown if some dolphins have become dependent on depredation as a principal feeding strategy, as has been suggested by some anglers.
Figure 1 - Entangled dolphin calf in Destin
The population status of dolphins in the Northern Gulf of Mexico is not well known, especially after recent hurricanes, red tides, and Unusual Mortality Events (UMEs). Increased interactions with sport fishing may indicate a shift in dolphins’ prey fish availability, suggesting ecological and habitat disturbance might underlie this problem. We speculate that discard requirements for undersized fish in the sport fishery also play a large role in exasperating dolphins’ persistence to depredate since fishing boats and piers serve as easy prey sources. Presumably, the unintentional feeding of dolphins reinforces the interactions and promotes the problem as younger dolphins learn depredation behaviors from adults, which may have significant effects on juvenile survival.
Figure 2 - Dolphin patrolling Okaloosa Pier
Our study sites are in Destin, Florida and Orange Beach, Alabama, where there are frequent reports of dolphins depredating sport fishing in the estuaries, at fishing piers, and at the near-shore reefs. The occurrence of these interactions appears to be year-round. Since January 2008, there have been two cases of dolphins being entangled in fishing gear in Destin (Fig. 1) and one unconfirmed report of a dolphin trailing a buoy. We have partnered with members of the charter fishing fleets in both locations and are also monitoring dolphin depredation activity at two Gulf fishing piers (Fig. 2). We have already identified numerous dolphins that frequent the fishing piers and two that travel between the piers, a distance of over 33 miles (Fig. 3). Our project addresses four aspects of this issue: 1) examine the extent of the fishery depredation problem, 2) assess impacts on dolphins, 3) investigate mitigation approaches, and 4) develop and disseminate educational information on “dolphin-friendly fishing tips”. Our objectives will be accomplished through direct observation of sport fishing, photo-identification of individual dolphins, angler surveys, and public outreach. We will be establishing community support for outreach opportunities as our study develops, and we look forward to reporting on our progress in the coming year.
This study is funded by the National Sea Grant Program of the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration under NOAA Grant NA07OAR4170511, the Mississippi-Alabama Sea Grant Consortium Project Number R/MG/BR-01A, and the Sea World Busch Gardens Conservation Fund.
Figure 3 - Panhandle project map with dolphins at fishing piers