What We Do
We answer the question: "What do fish eat and how much?"
Our mission is to understand who eats whom in marine waters of the northeast U.S. We examine the extent of predation and the impact of selective harvesting patterns on fish community dynamics. We document how predator and prey populations respond to one another. We assess the joint impact of harvesting and ecological interactions on these populations.
Unfortunately, it isn’t easy to observe fish predation and sample stomach contents in their natural environment, nor is it easy to measure these variables for an entire continental shelf. To accomplish our mission, our staff train sea-going staff to identify fish stomach contents. We also go to sea regularly and help collect the more than 10,000 stomach records which are added to the Food Habits Database each year. For copies of the training materials and to learn more please email Brian Smith or Stacy Rowe.
Our primary objectives are to measure fish trophic (feeding) interactions of the Northeast U.S.continental shelf ecosystem. Our emphasis is on fish near the ocean bottom and middle of the ocean and commercially-important invertebrates. Our research objectives are to:
Quantify the natural mortality of commercially-important species (due to predation) relative to fishing mortality.
Model species interactions.
Relate diet variability to various mechanisms (environmental and population-level processes).
Advance our understanding of the Northeast U.S. continental shelf ecosystem.
Projects: Products and Analyses
The program has four levels of products and analyses.
We produce descriptors of who’s eating whom (species profiles) across life histories of fish.
We examine what has happened to the fish community of the Northeast U.S. continental shelf. We use time-series modeling; hypothesis testing for differences across geographic regions, decades, depths, size classes, predators, etc.; and multivariate analyses.
Based upon our knowledge of the fish community, what will likely happen to the community composition, and how will this impact fisheries yield?
We produce generalized consumption estimates for key species with a theoretical examination of several approaches verified with field data. We are also interested in monitoring patterns that contribute to basic ecological principles observed from fish trophic interactions.
Our Food Habits Database is a source of information for peer-reviewed papers. It is the primary source for modeling consumption rates or predator-prey interactions in ecosystem assessments. In the past few decades, it has grown to include records of more than 650,000 stomachs from more than 150 predator species. Each year more than 10,000 stomach records are added by seagoing staff.
The database has two major sources: the Northeast Fisheries Science Center’s bottom trawl surveys, and “process-oriented” cruises. Both sources provide stomach content information; composition, total and individual prey weights or volumes; and length of prey.
The broad-scale trawl surveys cover continental shelf waters from Cape Hatteras, North Carolina to Nova Scotia, and extend from 1963 to present. Systematic fish diet sampling began in 1973 and has continued through today. The sampling program was initiated in the autumn of 1963; a spring survey was initiated in 1968. Seasonal surveys have also been conducted in summer and winter on an intermittent basis. Process-oriented cruises have been undertaken sporadically throughout this time series, and have a more geographical focus (e.g., Georges Bank).
Food Habits Data
Once collected, whether at sea or in the laboratory, the data are part of a computerized database. They are audited, documented, and archived for analysis. This extensive database is maintained on our network computer system. We continue to research and address various methodological issues related to these data, including:
Basic identification of prey.
Contrasting stomach volumes versus weights.
Interpretation of empty stomachs (are they blown, regurgitated, or truly empty?).
Unbiased estimators of stomach content data.
At-sea data entry.
Effect of time of day of sampling on stomach contents, etc.
Since 1985, all stomach samples have been primarily processed and prey identified at sea. However, we continually preserve the juveniles (< 12.5 cm) for all routinely sampled species for in-lab stomach processing. We have also preserved individual stomachs for data quality assurance during our bottom trawl survey approximately every 25th station, and from selected species during process-oriented cruises. To further ensure that the highest possible quality of data be collected at sea, we have conducted prey identification workshops. They provide many aids and guides to assist sea-going personnel in prey identification.
During the 1950-1960s, the Woods Hole Laboratory began surveying the marine benthic community. We cataloged and mapped the invertebrates which formed the fish forage base in the Northwest Atlantic Ocean. By the 1970s, the Lab's semi-annual, standardized fishery-independent groundfish surveys were routinely collecting food habits of a number of regional species. Today, routine monitoring and targeted investigations continue for more than 50 species.
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