CURRENT RESEARCH
I. Developing model-based based decision tools for evaluating impacts of fisheries on protected species
High levels of bycatch have been linked to population declines of many long-lived, late-maturing marine vertebrate species. However, only for a small fraction of species taken incidentally during fishing do we understand how much bycatch mortality is occurring or whether these levels are sustainable. This is due to a combination factors, including insuffient management resources (dollars) to collect adequate bycatch data and the challenges of studying population dynamics (e.g., reproduction and survivorship schedules) of long-lived highly migratory marine species. In addition to bycatch, fisheries may also affect marine vertebrates by affecting their habitat or prey availability, but again, quantifying such relationships is incredibly difficult.
In spite of these challenges, management agencies (such as the National Marine Fisheries Service) are charged with limiting impacts of fisheries on protected species such as marine mammals and marine turtles. But how do you set bycatch or fishing limits without knowing how much bycatch is too much, or whether fisheries are indirectly affecting protected species?
I am currently working on two projects in this research area. One is to develop a decision tool to help identify sustainable levels of incidental take for sea turtles. The approach is rooted in population demography and analagous in some respects to the Potential Biological Removal (PBR) framework used in the managment of marine mammals under the Marine Mammal Protection Act. The other project aims to identify marine mammal stocks most likely being affected indirectly by fisheries (via prey depletion). I am using a modification of the PBR equation in conjunction with historical information on fish stock abundance and ecological scaling principles to attempt progress in this research area.
II. Project GloBAL (Global Bycatch Assessment of Long-Lived Species)
Bycatch (incidental kill) by industrial and artisanal fisheries is a leading cause of population declines for many species of sea turtles, marine mammals, and seabirds around the world. Project GloBAL, an initiative of the Duke Center for Marine Conservation and Blue Ocean Institute, spent three years assessing global magnitude of fisheries bycatch for these taxa and has helped identify patterns that may yield inference for data-limited areas where bycatch occurs but is unquantified. Our work has involved comprehensive meta-analyses to address synthetic questions about bycatch (e.g., oceanographic correlates, bycatch vulnerability vs. life history), case study analyses based on observer-program data (e.g., demographic impacts of bycatch on populations, spatial patterns, etc), and developing protcols for efficiently gathering new bycatch information from data-limited areas. Here are a few specific projects I've been involved in since coming to Project GloBAL in January 2006:
A. Strandings-based model of cetacean demography and impacts of bycatch:
Marine mammals are notoriously difficult for obtaining information about survival rates, population growth rates, or population sizes. This makes management extremely challenging, because without these types of information, it is difficult to assess the conservation implications of observed bycatch levels for different species. Using age-structured strandings and bycatch data, I developed a Bayesian approach to estimate population parameters, and the impacts of bycatch on those parameters, for harbor porpoise (Phocoena phocoena) in the northwest Atlantic (Moore and Read 2008). I currently aim to update and apply this model framework to additional species interacting with Atlantic U.S. fisheries.
Harbor porpoise that died due to fishing net entanglement.
Photograph by and courtesy of Bo Haakansson,
Danish Society for the Conservation of Nature.
B. Rapid assessment of bycatch and fishing effort in data-limited fisheries:
We are only beginning to appreciate the potentially high impacts of small-scale fisheries around the world on marine mammal and sea turtle popoulations, due to high levels of mortality in fishing nets. However, reliable estimates of fishing effort and fishing mortality rates for these taxa are extremely limited in most artisanal fisheries of the world's developing areas. I have been collaborating with colleagues on Project GloBAL and partners around the world to develop a questionnaire-based protocol for obtaining semi-quantitative estimates of bycatch and fishing effort in data-limited fisheries. To date, information has been obtained from interviews with fishers in communities from Africa, Southeast Asia, and Jamaica. Our goal is to develop a standardized survey template that may be subsequently applied more broadly in relatively rapid and low-cost manner to help identify areas of the developing world where sea turtle and marine mammal mortality may be particularly severe, so that these areas can become foci for more intensive research and conservation efforts.
Artisanal fishing village in Jamaica.
Photographs by Peter Espeut.
C. Quantative evaluation of fisheries bycatch risk for marine mammals and seabirds:
Bycatch poses serious threats to marine mammal and seabird populations, but the fragmentary nature of bycatch information makes it difficult to establish international conservation priorities on this issue. Since current prioritizations are mostly species- and fishery-specific, based on individual case studies and expert opinions, we lack the global multi-species perspective needed to identify geographic regions where the greatest numbers of problems occur. In collaboration with Project Global colleagues, I have used information from the IUCN Red List and other sources to to describe bycatch risk for marine mammals and seabirds as a function of various species attributes within a logistic regression framework. One goal is to generate likelihood-based estimates of bycatch-risk for data-deficient species, thereby providing quantitative validation of expert opinion concerning bycatch concerns in data-poor areas. Another is to construct a map-based index depicting the global distribution of IUCN-classified and regression-estimated bycatch risk. These describe areas where cumulative bycatch problems are likely most severe.
