Research Objectives

  • Investigate the effects of various anthropogenic stressors, most notably fishing capture and handling, on the health and survival of elasmobranch fishes (sharks, stingrays and skates) and other fishes.
  • Examine potential factors explaining differences in the mortality rates and physiological stress responses observed between species.
  • Establish estimates of capture-induced immediate and delayed mortality rates of various fishes according to capture method and other factors that hold influence.
  • By deciphering the most detrimental aspect(s) of the capture and handling process for a given species or complex, establish strategies to reduce mortality (e.g. through the development of best capture and handling practices), or to reduce the rate of the incidental capture in the first place.

Research Overview

Humans pose many threats to health and balance of our oceans, including direct effects on ocean dwelling species. Our research program studies how marine fishes respond to those “anthropogenic” disturbances that tax these animals beyond the usual scope of their daily existence. Through the use of variety of field and laboratory based tools, we aim to reveal differences in how species physiologically and behaviorally cope with and recover from acute and chronic stressors, establish methods to reduce the stress imposed, and enhance survival of these fish species. In general, our work also aims to provide data that can be directly or indirectly utilized to inform conservation and/or management measures for vulnerable fish species.

While our program focuses on a variety of stressors and species, our work principally focuses on how commercial and recreational fishing capture/handling methods affect various fish species, particularly elasmobranchs (sharks, stingrays and skates). The overriding goal of this work is to establish mortality rates, and reduce stress and injury levels in fish captured accidentally and later discarded as “bycatch”, or fish captured and released for sport. For those species most vulnerable, some of the work also tests strategies to avoid these fish and therefore reduce catch rates in the first place.

Why elasmobranchs?

Due to factors such as slow growth, a long life span and low reproductive output, elasmobranch populations are in general very susceptible to overexploitation from human activities. For example, high levels of targeted commercial fishing effort and recreational fishing activities have caused major (reported) declines in the populations of many elasmobranchs species around the globe in recent years. However, the ecological footprint of fishing activities extends beyond the purposeful capture of these animals. Many elasmobranchs are also caught incidentally as bycatch, and although released, are still subjected to the cumulative physical and physiological rigors of capture, handling and deck-time (air exposure). Such treatments can be outright lethal, or incite eventual mortality after the animals have been returned to the ocean.

 

Post-Release Mortality of Atlantic Cod in the Recreational Fishery

 

Once vast, the Atlantic cod (Gadus morhua) population in the Gulf of Maine is currently struggling to recover from historic lows. Today, quotas and size limits are enforced in the recreational cod fishery in order to protect this rebuilding population. The survival rate of the cod discarded in accordance with these laws, however, is largely unknown. In collaboration with the Massachusetts Division of Marine Fisheries and University of New England, our project uses modern tracking technologies to evaluate the survival of Atlantic cod that are thrown back after capture in the recreational hook and line fishery. Our study seeks not only establish survival estimates, but also fishing and handling guidelines to minimize injury/stress/mortality of what is arguably the most commercially and recreationally important fish in New England waters.

Read more about this project on the Aquarium's Global Explorers Blog.

Condition and Discard Mortality of Skates in the Scallop Dredge Fishery

 

The incidental capture rates for skates (Family Rajidae) caught by demersal mobile fishing gears (i.e. otter-trawl and scallop dredge) in the Gulf of Maine/Georges Bank regions are at extremely high levels. Three of the five species from the Northeast Skate Complex indigenous to the Gulf of Maine are prohibited and must be released, while the other two are managed with strict catch limits, necessitating the return of any excess to the ocean. As such, the total discard rates for commercially caught skates in this region are high. Capture by these mobile towing gears coupled with handling of the catch on deck can lead to extensive physiological impairment, and can inflict severe physical trauma from crushing injuries, lacerations and mechanical stress from interactions with the gear. As such, it is important to understand the implications on survival in this group, which includes species of great management and/or conservation importance and concern.


Together with the Virginia Institute of Marine Science and University of New England, our current work aims to assess injuries sustained and estimate immediate and short term delayed mortality in skate species regularly caught as bycatch in the scallop fishery, which can inflict severe physical trauma from crushing injuries and interaction with the fishing gear. This work uses holding tanks to house skates on board the actual fishing vessels for the immediate few days after capture, allowing a direct observation of the fate of these animals. The impact of scallop dredge fishing on skate survival has been deemed a major priority area by fisheries management.

Conservation Physiology of Sharks and Rays in the Bahamas

 

Through our work and others, it has become clear that elasmobranchs vary widely by species in how they cope with capture stress from a given fishing gear/method. While some of the factors governing these differences are intuitive, others are more cryptic. For management and conservation purposes, it becomes important to not only explore the extent in which these species differ, but the underlying basis for why. Working with researchers at the Cape Eleuthera Institute in the Bahamas, we are examining how and why sharks differ in their tolerance to the stress of longline fishing capture, as well as how various sharks and rays respond to different types of acute and chronic stressors. This work involves a variety of smaller studies, with the broad goal to not only establish these species differences, but to devise methods that reduce the most detrimental aspects of human-induced stressors, while aiding the management and conservation of these vulnerable marine species.