Analyzing 19th Century Fisheries Records to Determine the Historical Abundance and Distribution of Gulf of Maine Cod
|William B. Leavenworth||UNH - Department of History||Associate Investigator|
|Andrew Cooper||UNH - Department of Natural Resources & the Environment||Associate Investigator|
|Karen Alexander||UNH - Department of History||Associate Investigator|
|Andrew Rosenberg||UNH - Department of Natural Resources & the Environment||Associate Investigator|
|W. Jeffrey Bolster||UNH - Department of History||Principal Investigator|
|Renee Dunn||UNH - Department of Natural Resources & the Environment|
|Catherine Marzin||UNH - Department of Natural Resources & the Environment|
|Emily Klein||UNH - Department of Natural Resources & the Environment|
|Loren McClenachan||Scripps Institution of Oceanography|
|Dmitry Lajus||St. Petersburg State University|
|Julia Lajus||European University of St. Petersburg|
|John Greene||UNH - Natural Resources and Earth System Science|
|Althea Marks||UNH - Natural Resources and Earth System Science|
|Steve Brennan||UNH - Department of History|
|Robert Gee||UNH - Department of History|
|Stefan Claesson||UNH - Department of Natural Resources & the Environment|
|Kate Magness||UNH - Department of Natural Resources & the Environment|
|Gwynna Smith||UNH - Department of History|
|Rene Poulsen||University of Southern Denmark|
|Lesley Rains||UNH - Department of History|
|Erika Washburn||UNH - Department of Natural Resources & the Environment|
|Tristan Law||UNH - Department of History|
Cod and other groundfish are of critical importance to the Gulf of Maine ecosystem and the New England fisheries. Most biologists, fisheries managers and policy experts agree that the Gulf of Maine cod fishery is in crisis today. All hope that the commercial fishery will remain an integral part of coastal New England's culture and economy. However, controversies exist about how to rebuild the stock and what population level is adequate for a profitable fishery and a healthy cod population. Inherent in those questions is the need for a clear understanding of long-term productivity. Central to the problem is that none of the stakeholders know very much about the historical nature of the Gulf of Maine cod population or about its productivity over the long term.
This project links maritime historians, biostatisticians, marine ecologists and policy experts from UNH to look at the historical dynamics of the cod population. It will reconstruct cod population dynamics for the mid-19th century Gulf of Maine using data obtained from approximately 650 historic fisheries logbooks, fishing agreements and other customs records.
From 1852-1866 cod fishermen recorded the catch per man (Catch Per Unit Effort) and their geographic location in their logs for almost every day of the fishing season. Data sets compiled from these logs are suitable for analysis using modified fisheries stock assessment models, generating metrics for cod population size in numbers of fish, total biomass and average fish size. Furthermore, GIS permits the mapping of geographic and seasonal distribution of cod as well as seasonal and geographic variations in catch and fish size.
This study follows a similar investigation of the logbooks from the Scotian Shelf deepwater codfishery. That fishery showed a marked decline in catch from 1852-1859. In contrast, preliminary analysis of the Gulf of Maine logs indicates that this near shore fishery may have been sustainable 150 years ago.
The population metrics generated can be of enormous importance to fishery managers. The metrics extend baselines for cod stock back to a state not yet exploited by mechanized fishing. Managers and policy makers can use these baselines in formulating stock restoration goals. Population distribution and migration patterns of cod in the 1800s can be compared to those obtained for the Gulf of Maine today to aid in the development of area-based management systems. Reconstructing cod stock in the pre-industrial Gulf of Maine extends the scientific framework of marine ecology back 150 years to retrieve results unobtainable today by traditional scientific experimentation.
The objectives of this project are to determine population size, demographics and migration patterns for Gulf of Maine cod in the mid-19th century. Data will be derived from historic fisheries logs and ancillary documentary sources, and analyzed using modern fisheries stock assessment models. These results will provide end user scientists, fisheries managers and policy makers, as well as the interested public, with baselines for cod populations before the advent of mechanized fishing.
Spatial and temporal resolution in Gulf of Maine data will allow us to calculate spatially-explicit estimates of CPUE throughout a fishing season to fit a series of regression models and non-equilibrium surplus production models. Mixed-effect models will estimate population-wide parameters (e.g., fixed-effects) as well as spatially-explicit parameters (e.g., random-effects). The significance of random effects will be tested using likelihood ratio tests.
This project directly addresses debates on rebuilding cod stocks in the Gulf of Maine by supplying 19th-century cod population baselines. It contributes to discussions on biological reference points, provides parameters for ecosystem dynamics, and adds historical perspectives to questions of geographical distribution and area-based management. End users are the New England Fisheries Management Council, the U.S. Commission on Ocean Policy, the Census of Marine Life, the National Marine Fisheries Service, fishermen and the general public.
Historic Records Provide 19th Century Baseline for Cod Population Estimates
Comparison of Cod Population Structures Indicates Reproductive Health
NHSG-funded researchers analyzed 19th century fisheries records to estimate the population structure for cod in the Gulf of Maine in the 1860s and compare it to present-day structure. In 2012, researchers determined that the graph of the population curve for cod landed from 1861-1865 is similar to the graph for cod landings from 2003-2007. Large cod were present in about the same proportion in both groups, although the quantity caught was different. Larger-sized cod are typically better breeders, so this may represent improved spawning success and reproductive health. The data indicate that current cod population structure, despite being low, resembles that of a much healthier historical population. These results provide a more detailed view of population structure for improved fisheries management decisions.
In 2012, NHSG-funded researchers analyzed 19th century fisheries records to determine the historical importance of inshore fishing grounds. Using landings from Frenchman’s Bay vessels in 1861, they estimated that more than 91% of the catch in the bay’s Customs District was harvested near shore — within 20 miles of a protected anchorage, with the average being 6.32 miles from shore. These historical fishing “microgrounds” demonstrate the critical importance of coastal ecosystems to cod populations. This research will enable resource managers to gain a better understanding of the importance of inshore fishing grounds for sustainable cod stocks.
Records of Cod Population Structure Indicate Historic Complexity
Using NHSG funding in 2012, researchers used landings from Frenchman’s Bay vessels in 1861 to calculate and plot the average daily weight of cod to show spatial and temporal changes during various seasons and at different scales. The data indicated that cod had distinctive size cohorts and displayed seasonal migration, with larger cod appearing in early spring and smaller cod replacing them during late summer. Within a single season schools of cod appeared and occupied individual fishing areas for a time, and were then displaced by successive groups. These data suggest a more complex population structure than that of present-day stocks. Results from this research provide a more comprehensive view of cod populations that will help inform fisheries management decisions.
Records of 19th Century Cod Stomach Contents Indicate Historic Feeding Habits
In 2012, NHSG-funded researchers analyzed 19th century fisheries records to determine the historical feeding habits of cod in the Gulf of Maine. When researchers examined documents from the 1860s, the descriptions of cod stomach contents indicate the fish ate mostly crabs, clams, herring and squid, with only one small lobster detected in all 168 stomach samples. Vessel log books from that era indicated that fishermen recognized the importance of those species for supporting cod populations but made no mention of lobsters — in present day, cod are commonly thought of as one of the main predators of lobsters. The stomach contents from the 19th century indicate that a recovery of the cod fishery may not adversely affect the lobster fishery unless other forage species in the system have already declined. This research will help inform resource managers of cod feeding habits and ecosystem components for improved fisheries management decisions.
Landings Estimate for cod in 1861
Available from the National Sea Grant Library (use NHU number to search) or NH Sea Grant
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