Analyzing 19th Century Fisheries Records to Determine the Historical Abundance and Distribution of Gulf of Maine Cod

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Project Type: 
Research
Project Number: 
R/MED-3
Inception Date: 
2004
Completion Date: 
2006
Theme Area: 
Fisheries Resources

Participants:

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

Students Involved:

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
Abstract: 

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.

Objectives: 

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.

Methodology: 

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.

Rationale: 

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.

Accomplishments: 
2012

Historic Records Provide 19th Century Baseline for Cod Population Estimates

In 2012, NHSG-funded researchers analyzed 19th century fisheries records to estimate historical cod landings in the Gulf of Maine. They used landings from Frenchman’s Bay vessels in 1861 and tested a range of distributional assumptions in their calculations to estimate that between 62,600-78,600 metric tonnes of cod were caught that year. This estimate indicates that the cod population in the 1800s was much more productive than it is today, representing a decline of more than 89%. These historical population estimates will enable resource managers to use a more accurate baseline for their model calculations for improved fisheries management decisions.

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.

Historic Records Indicate Importance of Inshore Habitats for Cod Stocks
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.

2011

 
Book Chapter Details Daily Life in the New England Cod Fishery in the mid-1800s, as well as Catch Estimates from the Gulf of Maine
NHSG-funded researchers are working to digitize and extract data from fish inspector reports and fish commission reports in Maine and Massachusetts variously ranging from 1804-1908. As part of this effort, one of the researchers contributed a chapter to the book In Our Own Words: New England Diaries, 1600 to the Present. The book chapter provides personal records of life at sea from the nineteenth century cod fishermen’s logs. In addition to providing a more well-rounded view of the daily lives of fishermen, the book chapter also includes the estimates of the number of cod that were caught and at what location. This information is useful for fisheries managers who need historic population estimates in order to better manage the current fish stock.
 
Book Chapters Describes Daily Life and Catch Estimates from the Scotian Shelf
NHSG-funded researchers are working to digitize and extract data from fish inspector reports and fish commission reports in Maine and Massachusetts variously ranging from 1804-1908. As part of this effort, one researcher edited the book “Shifting Baselines: The Past and Future of Ocean Fisheries” and the others co-wrote two chapters for the book, which presented material from the historic New England cod fisheries. One of these two chapters described the Scotian Shelf fishery, uniting descriptive narrative about historical life at sea with the scientific analysis of the decline of catch and cod stocks. The collapse of the fishery is described in the words of the fishermen who suffered the consequences, and the abundance estimate of cod on the Scotian Shelf is explained in historic terms. The other chapter describes how lessons learned from both the Frenchman’s Bay and the Scotian Shelf fishery are applied to current management strategies and the gratifying increase in alewife abundance after the removal of the Edwards Dam in Maine is cited as good news for this endangered species. Shifting Baselines is the first book on the subject and investigates how historic perspectives apply to the crisis in fisheries management.
 

Landings Estimate for cod in 1861

Estimated cod landings in the Gulf of Maine in 1861 at between 62,600 and 78,600 mt, by scaling up the landings from Frenchman’s Bay vessels, and after testing a range of distributional assumptions and propagating uncertainty throughout. The range depends on the multiplier used to convert from cured to round weight, but in either case is more than an order of magnitude greater than current landings today, and comparable to the goal for Spawning Stock Biomass (SSBMSY) of 82,830 mt (NEFSC 2008). This confirms Lotze and Worm’s conclusions that harvested marine animals have declined more than 89% on average since historical times (2009). This shows that the cod population in the 1800s was enormously more productive than it is today, which implies that the marine ecosystem was also profoundly different (Alexander et al. in press).
 
Population Structure
Determined a population structure for Gulf of Maine cod in the 1860s. The graph of the curve for cod landed from 1861 to 1865 is surprisingly similar to the graph for landings from 2003-2007 (NEFSC 2008). Both these graphs show a similar distribution of landings by size. Large cod were present in about the same proportion in both groups, although the quantity of cod caught was very different. (An exception is that no 2kg cod showed up in the modern landings because mesh size is now regulated.) However, both of these distributions are quite different from the graph for 1996-2000. Then 83% of the cod were between 2 and 4 kg, with cod over 6kg at 38% of the current quantity (NEFSC 2008). This may show that, while population size has not grown appreciably, population structure seems to have improved dramatically, and resembles that of a demonstrably healthier historical population. Since large cod are better breeders this may be a necessary condition for improved spawning success (Alexander et al. in press).
 
Evidence of Distinctive Size Cohorts and Seasonal Migration
Calculated and plotted the average daily weight of cod to show spatial and temporal changes during the season and at different scales. Generally, larger cod averaging 15 lbs. or more appeared in late March and early April, and again in November. Smaller fish averaging less than 10 lbs. each took their place during late summer and early fall. Smaller scales show that cohorts varying substantially in size occupied different parts of the region at the same time. Within a single season schools of cod appeared, possessed individual fishing areas for a time, and were displaced by successive groups. This suggests a population structure for cod more complex than any recently observed (Alexander et al. in press, Ames 2004, Bigelow and Schroeder 1927, Goode 1887).
 
The Importance of Inshore Grounds
Showed that 91.62% of the catch in the Frenchman’s Bay Customs District was taken near shore within 20 miles of a protected anchorage, a range roughly equivalent to that of small, motorized lobster boats today. The inshore fishery was enormously productive in a region that scarcely fishes for cod at all today. Frenchman’s Bay logs describe 56 hitherto uncharted fishing locations with landmarks, ranges and bearings. Averaging 6.32 miles from shore, these microgrounds were clustered near or within broad bays perforating the Maine coast, and were exploited by large vessels and small boats at the same time. Several vessels recorded catching cod at anchor in port. The coastal ecosystem receives little or no attention from marine conservation, yet history indicates that it is of critical importance to cod (Alexander et al. in press).
 
Mortality Rate
From the population structure we calculated a mortality rate for cod in 1861. However, fishing mortality turned out to be higher than we anticipated. We are still studying this to try to determine what it may mean. While Cashes Ledge and Jeffrey’s Bank are important today, a combination of traditional fishing patterns, economic strategy and the sailing ability of traditional vessels insured that they were rarely visited in the 1860s. Thus high inshore fishing mortality may have been mitigated by under-utilized grounds that served as defacto protected areas. This is the first mortality rate calculated from historical landings records.
 
Ecosystem Information and Feeding Habits
Fishermen’s descriptions of bait abundance are statistically significant indicators of cod landings, indicating that ecosystem descriptions in the log are not only accurate, but list what the fishermen thought were the ecosystem components necessary to support cod populations. The species they described most often were herring, menhaden, and clams. Lobster did not figure into their thinking at all. We found four lengthy descriptions of cod stomach contents taken in the 19th century out of 168 fish caught from Long Island Sound to the Bay St. Lawrence. The most common forage species were crabs, clams, herring and squid. Only one 4 inch lobster was found. This indicates that a recovery of the codfishery may not adversely affect the lobster fishery, unless other forage in the system has also declined (Alexander et al. in press).
 
First approach using an historical fishery as a lens on the Gulf of Maine ecosystem
When we embarked on this study, researchers were focusing on estimating baselines, and we had just estimated the cod population on the Scotian Shelf in 1852. We conceived of our results as stand- alone papers at the time. We found as we worked, however, that each result was intimately connected to the whole and that, taken together, they provided an ecosystem snapshot of the Gulf of Maine in the 1860s with precision that had not been achieved before. For this reason, we combined all six results, along with their impacts, into one long paper to show that historical baselines can be assembled into an ecosystem portrait, and that one fishery can act as a lens on an entire ecosystem in the past as well as today.
 
Management recommendation 
We propose creating Coastal Protected Areas and corridors linking these areas to MPAs and other management areas. Penobscot Bay, an area of considerable conservation interest that once supported a prolific coastal ecosystem, would be a good candidate.

Publications

Available from the National Sea Grant Library (use NHU number to search) or NH Sea Grant

Journal Article

  • Bolster, W. (2008). Putting the ocean in Atlantic history: maritime communities and marine ecology in the Northwest Atlantic, 1500-1800. American Historical Review 113(2):19-47, February 2008.
  • Bolster, W. (2006). Opportunities in marine environmental history. Environmental History 11:567-597, July 2006.
  • Willis, T., K. Wilson, K. Alexander and W. Leavenworth (2013). Tracking cod diet preference over a century in the northern Gulf of Maine: historic data and modern analysis. Marine Ecology Progress Series 474:263-276, 2013.
  • Grasso, G. (2008). What appeared limitless plenty: the rise and fall of the nineteenth-century Atlantic halibut fishery. Environmental History 13(1):66-91, January 2008.
  • Alexander, K. et al. (2009). Gulf of Maine cod in 1861: historical analysis of fishery logbooks, with ecosystem implications. Fish and Fisheries 10(4):428-449, December 2009.
  • Leavenworth, W. (2008). The changing landscape of maritime resources in seventeenth-century New England. The International Journal of Maritime History 20(1):33-62, June 2008.
  • Rosenberg, A., W. Bolster, K. Alexander, W. Leavenworth, A. Cooper and M. McKenzie (2005). The history of ocean resources: modeling cod biomass using historical records. Frontiers in Ecology and the Environment 3(2):84-90.

Thesis/Dissertation

  • Klein, E. (2008). A new perspective: Atlantic herring ("Clupea harengus") as a case study for time series analysis and historical data. Master's Thesis, University of New Hampshire.
  • Claesson, S. (2008). Sustainable development of maritime cultural heritage in the Gulf of Maine. PhD dissertation, University of New Hampshire.
  • Magness, K. (2005). Development of fishing policy in the Gulf of Maine, late 19th century. Master's Thesis, University of New Hampshire.

Book Chapter

  • Rosenberg, A., K. Alexander and J. Cournane (2011). Management in the Gulf of Maine. In J.B.C. Jackson, K. Alexander and E. Sala (Eds.), Shifting Baselines: the past and the future of ocean fisheries (pp. 177-191). Washington, DC: Island Press.
  • McKenzie, M. (2004). Salem as Athenaeum. In: Salem: Place, Myth and Memory, D. Morrison and N. Schultz, eds., pp. 91-105.
  • Bolster, W.J., K. Alexander and W. Leavenworth (2011). The historical abundance of cod on the Nova Scotian shelf. In J.B.C. Jackson, K. Alexander and E. Sala (Eds.), Shifting Baselines: the past and the future of ocean fisheries (pp. 79-113). Washington, DC: Island Press.

Proceeding

  • Alexander, K. (2009). "so ends this day": personal records of life at sea from nineteenth-century New England cod fishermen's logs. In Our Own Words: New England Diaries, 1600 to the Present Volume 1: Diary Diversity, Coming of Age; The Dublin Seminar for New England Folklife Annual Proceedings 2006/2007, Peter Benes, Ed., pp.79-93.
  • Leavenworth, W. (2006). Opening Pandora's box: tradition, competition and technology on the Scotian Shelf, 1852-1860. Studia Atlantica 8:29-49, 2006.

Book

  • Jackson, J.B.C., K.E. Alexander and E. Sala (editors). Shifting baselines: the past and the future of ocean fisheries. Island Press, 2011.