Pre-1900 – late 1930s

Recent observations of cod movement across stock boundaries are generally consistent with historical tagging data as well as information from other stock identification approaches. This working paper provides a historical context in which to consider recent tagging data for spatial delineation of cod stock assessments (TOR C). Introduction The objective of this report is to review the literature available for stock identification of cod off New England. The review is focused on tagging studies, but also refers to relevant information from other approaches to determine spatial population structure, though not comprehensively. The organization is initially chronological, to illustrate the historical development of perspectives on cod stock structure, but conclusions are based on multidisciplinary synthesis of information pertaining to movement across current stock boundaries. Review of Previous Research Pre-1900 – late 1930s Goode (1884) consolidated the earliest information regarding the fisheries of the New England area. This work catalogued the cod fishing grounds, cod fishing methods, and predominant cod fishing ports through a series of fisherman interviews. Goode’s (1884) documentation established a baseline for which cod catch statistics were gathered by identifying the key ports within the region. Annual reporting of catches initiated in 1893 (Serchuk and Wigley 1992). The reporting was temporally consistent, although occasionally ports were missed during any year. Goode (1884) delineated fishing grounds in his earliest work, however apparent inconsistencies between captains required a redefinition of fishing grounds by the late 1920s (Rich 1930). During the early 1900’s tagging studies were conducted in association with cod hatcheries. Hatchery experiments began in Gloucester, MA in 1884 (Tarr 1884), and by the 1900’s a permanent hatchery had been established in Woods Hole, MA (Smith 1902). Smith (1902) conducted the first exploratory tagging experiment at the Woods Hole hatchery. Cod that had been collected on Nantucket Shoals for brood stock were tagged and released of Woods Hole, MA after they spawned. Recaptures from this experiment Working Paper C.2 Cod Tagging & Stock Identification (2007 GARM WP3B) 2 indicated that many cod returned to Nantucket Shoals, and some moved southward to the middle Atlantic Bight (Smith 1902). A second tagging investigation was initiated in 1923 (Rich 1925) and continued annually through 1932 when funding diminished (Higgins 1934). The initial scope of this project was to repeat Smith’s (1902) experiment tagging and releasing cod at Woods Hole and also to carrying out tagging on Nantucket Shoals (Rich 1925; Schroeder 1930). Reports of this work were filed annually with the U.S. Commissioner of Fisheries fiscal reports (Rich 1925; 1926; Higgins 1927; Schroeder 1927, 1930; Higgins 1928, 1929, 1930, 1931, 1932, 1933, 1934) and at meetings of the North Atlantic Commission of Fisheries Investigations (NACFI 1932, 1935, 1939). These reports provide precise reporting of the dates, location, and number of tagged cod, but the conclusions are often generalized and lack specific details. By 1928 a general perception of cod stock structure had been formed (Higgins 1929): • A seasonally migrating group between the grounds of southern Massachusetts and North Carolina. • A Nantucket Shoals group with components that move westward and eastward in the summer. • Massachusetts Bay fish that tend to migrate to the south • Relatively sedentary groups ranging from northern Massachusetts Bay to eastern Maine. • In the middle of the Gulf of Maine some banks had stationary stocks while other individuals appeared to migrate randomly out of the area in all directions. • The offshore banks of Georges and Browns Banks appeared connected. Schroeder (1930) provided extensive analysis of the cod tagging that occurred primarily along the southern shore and specifically at Nantucket Shoals. Furthermore, Schroeder conducted an investigation in growth patterns through scale ageing and length frequencies collection. Schroeder (1930) provided a view of New England cod stock structure, stating: “The stock of cod living on Nantucket shoals, consisting chiefly of young adult and nearly adult fish, is for the most part distinct from that living to the north and east of Southern Massachusetts, for there is no general intermingling of the fish belonging to these regions...only a very small percentage of the Nantucket cod stray to the north and east annually, and, conversely, only a few cod tagged to the north and east stray to Nantucket Shoals” “A large part of the Nantucket Shoals cod population make a fall migration into the Rhode Island-North Carolina region, where most of them remain until the spring. These fish are joined by others from the North and east of Cape Cod; but that southern New England cod form the bulk of the fish which occupy these wintering grounds is indicated by the paucity of recaptures there of fish tagged to the northward and eastward of Cape Cod and by the general similarities in length frequencies between the population in this wintering region and the summer cod on Nantucket Shoals. In the spring the fish return eastward, the majority of them stopping to summer on Nantucket Shoals, but others, chiefly the larger Cod Tagging & Stock Identification (2007 GARM WP3B) 3 fish, most of which probably came from the north and east of Cape Cod, continue on to deeper water.” “Part of the cod living on Nantucket Shoals emigrate eastward to the Chatham-South Channel region during certain summers...the size of the fish but temperature, too, appears to influence this emigration...fewer cod took part in the summer eastward emigration than in the fall westward migrations.” Preceding the investigation on Nantucket Shoals, Schroeder switched focus to the coastal Maine and offshore bank stocks. Unfortunately, detailed analysis from these investigations was never published. What results have been published include: Browns Bank: Major pathway of movement was North and Northeast with a little to the south and West (Higgins 1931). Georges Bank: Most fish stayed on the Bank with movement to Browns Bank and slightly less to Nantucket Shoals and Southward (Higgins 1931). Maine Coast: Most returns local, those fish that did migrate tended to move East (Higgins 1933). The Maine coast stock was not thought to be a feeder to the offshore banks (Higgins 1934). This early series of tagging investigations provided the first information on movement patterns of cod off New England, but they were not quantitative. Documentation is incomplete, and conclusions are somewhat subjective. Furthermore, much resolution in data may have been forgone due to an estimated 60-70% tag loss (Schroeder 1927, Higgins 1929) 1930-late 1950s. Haddock had become increasingly important by the late 1920’s (Higgins 1928; Serchuk and Wigley 1992), and cod catches along Southern New England had declined severely by 1934 (Higgins 1935). These fluctuations in landings prompted efforts to improve fishery monitoring and control factors affecting the fishery (Rounsefell 1948). A system of geographically defined statistical reporting units was developed based upon the European system. Units in the Gulf of Maine region were designed to encompass historically important banks while in the Great South Channel and Georges Bank they were designed around the apparent natural effort distributions of the offshore fishery (Rounsefell 1948; Figure 1). Catch statistics and later trawl survey data became tabulated by statistical areas (Rounsefell 1948; Halliday and Pinhorn 1990; Serchuk and Wigley 1992). Although no investigations into New England cod occurred during this time period, a tagging study was conducted in Nova Scotian waters (McKenzie 1956). 1950-1960 Towards the end of the 1950’s there was a renewed interest in cod stock structure. Wise (1958) conducted a repeat of Smith’s (1902) and Schroeder’s (1930) investigation of the cod along the southern New England Mid Atlantic Bite region. This group had already been identified as exhibiting a unique seasonal migration between Nantucket Shoals and the Mid Atlantic region. Wise (1958) conducted his tagging along the southern New Jersey shore, finding the same seasonal pattern describe by Schroeder (1930) and in the Commissioner of Fisheries reports. Based upon the presence of Cod Tagging & Stock Identification (2007 GARM WP3B) 4 spawning individuals along the New Jersey coast, he concluded that these cod spawn in the south during the winter and migrate northward to feed during the summer, however. This period was punctuated by a significant effort to consolidate the information on stock structure along the Western Atlantic coast (Halliday and Pinhorn 1990; Serchuk and Wigley 1992). Wise and Jensen (1960) performed a preliminary investigation on cod stock structure finding that in New England: “While cod is the subject of the major fishery in the Convention Areas and yearly landings of cod usually surpass those of all other species combined in Subareas 1, 2, 3, and 4, they are of subordinate importance in Subarea 5. In addition, about one-half or two-thirds of the cod landing in Subarea 5 are incidental to the haddock fishery. These facts have functioned to de-emphasize cod research in the Subaraea: for about twenty-five years following 1930 there was no research in progress.” “...the most important single population is that of eastern Georges Bank, which apparently mixes little with the more westerly and northerly groups although some of the large and older fish do appear to wander off to join the populations of western Nova Scotia (Subarea 4). West of the shoals of Georges Bank (about 68W.) there is another population which summers in the great South Channel (about 69W.), particularly on the western side, and which spends the better part of the rest of the year inshore in the Nantucket Shoals-Chatham region. North of this group of fish are those of the Gulf of Maine, one or more sedentary stocks.” “Joining the Nantucket Shoals-Chatham fish in the summer are fish whose winter habitat is outside the Convention Area. They migrate along the Rhode Island, Long Island and New Jersey shores in the autumn, some years reaching as far as North Carolina (about 35N.), then return in spring to summer in southern New England waters again.” Templeman (1962) summarized this report and others to delineate Western Atlantic cod stocks (Figures 2). Some boundaries of the statistical reporting areas were readjusted following these reports to more suitably encompass the stocks in question (Halliday and Pinhorn 1990). Sherman and Wise (1961) used of parasites as biological tags to determine stock structure of cod. Their one-year study found that the prevalence of the gill parasite increased in the shore fish as latitude increased. Prevalence was relatively low in all offshore samples. They concluded that there are probably three stocks in the New England area consisting of the Gulf of Maine where parasitism was higher, Georges Bank where parasitism was relatively low, and Southern New England where no parasitism was found. Their stock boundaries coincided with the statistical areas defined earlier by Rousenfell (1948). Wise (1963) completed a broad scale, four-year tagging investigation to study New England cod stock structure (Figures 3-5). Through a synthesis of tagging results, commercial length frequency data, the earlier parasitic investigation, and a meristic study, Wise (1963) concluded on New England Cod stock structure that: 1. “The cod of the offshore banks (Georges and Browns) are closely related to the fish of the southwestern Nova Scotia coast.” Cod Tagging & Stock Identification (2007 GARM WP3B) 5 2. “The cod of the Gulf of Maine, probably divided into many subgroups, and receiving considerable recruitment from the south.” 3. “The cod of southern New England and the South Channel.” 4. “The New Jersey coastal cod, which spend part of the year mingled to a greater or lesser degree with the southern New England fish.” Furthermore, Wise (1963) went on to describe how the bathymetry and hydrography of the region shape the structure of cod stocks. Northern stocks seemed to be defined by bathymetry; on Georges Bank they are divided by western shoals of the Bank, at about 68W, while the South Channel was divided from the Gulf of Maine by the constriction at the North end of Cape Cod. Hydrography played a roll in defining the NJ coastal cod and the growth differences between Gulf of Maine fish and those to the South (Wise 1958). 1960-1980 The history of cod management on Georges Bank during this period is documented by Serchuk and Wigley (1992). There was a major shift from international management through ICNAF to internal management starting in the early 1970s. ICNAF division 5 was subdivided into area 5Y (Gulf of Maine) and 5Z (Georges Bank) in 1972 (Serchuk and Wigley 1992). An initiative to advance stock assessments of New England cod resources led to a multidisciplinary review of information on spatial population structure to define operational management units with similar demographic parameters for population modeling. Pentilla and Gifford (1976) compared cod growth and mortality rates between the Gulf of Maine, Southern New England and the South Channel region (Nauset), and on Georges Bank. They found “highly significant differences between areas (P<0.01), except for the age 3 autumn comparison between Georges Bank and the South and Nauset areas (P>0.05). For age 4 and older cod the mean lengths at age from these two areas are very similar” (Pentilla and Gilford 1976). Similarities in growth rates eventually led to the consolidation of the Georges Bank stock with the South Channel and SNE stock into an operational stock. The principal spawning times and locations for cod were described by Colton et al. (1979). Serchuk and Wood (1979) document the evidence for a consolidation of previously recognized stocks, including information on historical fisheries trends, management structure, distributional data, trends in trawl survey data, mortality estimates, growth investigations, commercial indices of catch-per-unit-effort and commercial catch composition. They also demonstrated the management implications of different life histories and fishery patterns through yield-per-recruit analyses, illustrating different population dynamics and productivity of the newly delineated stocks. Serchuk and Wood (1979) concluded that the similar trends in growth rates, trawl survey indices, and commercial catch compositions between George Bank and more southern areas, as well as the apparent absence of juvenile cod from the Mid-Atlantic region justified a common approach to assessment and management for both areas. They state: “The question of biological stock identity of the southerly cod populations may be moot relative to management concerns. If the similarities between the Southern New England-Middle Atlantic and Georges Bank cod populations result from similar biotic and environmental factors, management measures applied to the two groupings as a unit should Cod Tagging & Stock Identification (2007 GARM WP3B) 6 produce similar responses within each group. Contrariwise, if the similarities between the groups reflect the movement of Georges Bank fish southward, then only one biological stock exists and management measures applied similarly in both regions should produce a uniform impact” This operational stock definition has been applied to New England cod resources since the late 1970s.