My project focuses on Cuban dogfish and gulper sharks, two of the most commonly captured bycatch (non-target) species in deep sea fisheries worldwide. These sharks are representative of entire groups of related species at depths between 200 and 1,000m deep. They are often caught accidentally in commercial snapper and grouper fisheries and experience high mortality rates when pulled to the surface due to severe temperature, pressure, and light related stress. If they are alive at the boat, they are either released as bycatch and presumed to survive, or, conversely, killed at the boat under the assumption that none will survive after release.
A past study in Eleuthera, The Bahamas, deployed 11 satellite tags on gulper sharks, and received data from only two. Both of these were badly damaged and showed signs of predation close to the capture event. As such, we believe that even those sharks released alive are being either consumed on the way back down or perish shortly thereafter as a result of capture. On the other hand, deep sea trawl fisheries assume that all captured sharks will not survive, and as such vessels remove their livers before throwing them overboard. If our data suggest that some species can survive, then a selective release measure can be implemented for animals caught in the appropriate depth zones.
So how can fisheries models assume 100% mortality, or nearly 0% mortality, without basic estimates of post-release survivorship? The answer is that they simply cannot. As you can imagine, this leads to a troubling conclusion: fisheries models are likely underestimating the impacts of capture on deep sea shark populations or, through blanket regulations, allowing the killing of sharks that would otherwise make it.
As such, our research aims to fill gaps in our ability to responsibly manage fishing effort in the deep sea. It is the next step in a series of ongoing projects out of the FSU Coastal and Marine Lab and our collaborators at the Cape Eleuthera Institute.
Management decisions rely on accurate estimates of at-vessel mortality and post-release survivorship. For these sharks, we have little to none of the latter.
Our project will help managers put the true price on the effects of fishery capture in the deep sea. The gulper sharks and Cuban dogfish were not chosen randomly; they are representative of the dominant groups of sharks captured in deep sea fisheries worldwide. As such, our research will improve the ability of fisheries models to predict the true cost of bycatch in temperate and tropical waters around the world for not only these species, but entire assemblages of related fishes.
Furthermore, it will set the stage for future studies on the habitat use and migration patterns of these animals, particularly research documenting the long-term impacts of a capture event or even a toxic oil spill.
This project will serve two main objectives: a research component and an education component.
This funding will cover the majority of equipment costs required for me to complete this project. Most of what we purchase will be useful for studies in the future as well, so the funding will go a long way!