Age, Growth and Sexual Maturity of Cod (Gadus morhua L.) in the Newfoundland Area, 1947–1950

Commercial recaptures of 26% (22.5% in years after the tagging year) of 18,822 Atlantic cod (Gadus morhua) 50 cm or more in length that were tagged mainly in the feeding season at 13 localities in the Newfoundland area in 1954–55 elucidated migrations and intermingling of cod of various stocks or stock complexes. Cod of the northern Gulf of St. Lawrence stock migrated southward from the Strait of Belle Isle to winter on the northern side of Cabot Strait and vicinity, mingling there with the Burgeo Bank stock. Cod of the Newfoundland–Labrador complex tagged at three sites mingled along the east coast of Newfoundland and off southern Labrador and with cod of the northern Gulf stock near the Strait of Belle Isle, of the Avalon–Burin stock complex off the Avalon peninsula, and of a Grand Bank stock on the northern part of the bank. Though cod tagged off the Avalon peninsula and on St. Pierre Bank were recaptured mainly near the tagging sites, some moved as far north as Labrador, to the southern Grand Bank, and to Cabot Strait. Fish tagged on the northwestern Grand Bank were recaptured mainly at the tagging site but also elsewhere on the bank and off the east coast of Newfoundland. Those tagged on the Southeast Shoal of the Grand Bank were recaptured mainly on the southeastern part of the bank though some moved as far as southeastern Newfoundland. Those tagged on Burgeo Bank mingled with the Avalon–Burin stock complex, including the St. Pierre Bank component, but mainly with the Northern Gulf stock in winter–spring near Cabot Strait.Cod 90–129 cm long at tagging were recaptured at shorter distances from the tagging sites than 50–89-cm cod. Tagging–recapture distances also increased with increasing age for cod of the smaller length ranges on tagging. In their vertical movements, most tagged cod moved to shallow water in late spring or early summer and retreated gradually to deeper water from late summer to early spring. Some remained in deep water throughout the year.Recapture rates at different size ranges varied with area but were not greatly different at length ranges from 50–59 to 80–94 cm, which included 95% of the tagged cod.

Commercial fishing practices on offshore juvenile flatfish nursery grounds on the Grand Banks of Newfoundland

We examined interannual variability in the timing of spawning of female cod Gadus rnorhua from 1947 to 1992 in 3 regions off Newfoundland, Canada, in the northwest Atlantic. Maturity data, assessed by visual examination of dissected gonads of cod collected by research trawls, were analysed with probit regressions to identify the day of each year on which 50% of females had ceased spawnlng (which we refer to as spawning time) on northern [Northwest Atlantic Fisheries Organisation (NAFO) Division 3L] and southern (3NO) Grand Bank and on St. Pierre Bank (3Ps). We minimized the bias in our estimates by separating sampling variability and interannual variation in age structure from true interannual variability in reproduction. Among regions, average spawning time (mean -t SD) varied from Days 157 + 18 (June 6 ) and 139 * 16 (May 19) on northern and southern Grand Bank, respectively, to Day 135 2 24 (May 15) on St. Pierre Bank. Interannual differences in spawning time were significant within 3L (1948-1991), 3 N 0 (1947-1992), and 3Ps (1953-1987) (likelihood ratlo tests; p < 0.001). Interannual variation in spawning time was significantly associated wlth variation in water temperature prior to spawning in 3L and in 3Ps although the signs of the associations differed between regions, casting doubt on the hypothesis that the timing of cod reproduction represents an adaptive response to temperature change. The negative correlation between temperature and spawning time in 3L can be explained by the positive influence of temperature on gonad development. In 3Ps, we attribute the early spawning dates in years characterized by cold bank temperatures to (1) a thermal barrier Imposed by sub-zero temperatures on spawning migrations from the continental slope to the shelf, and to (2) increased rates of gonad development, and an earlier readiness to spawn, experienced by cod 'forced' to prolong their residence in warm slope waters. Our analyses indicate that cod spawning time varies significantly among years, demonstrate how the effects of temperature on cod reproduction depend on regional hydrography, and underscore the importance of separating variation in sampling protocol and age structure from true interannual variability in spawning time.

Inspection of the fillets of cod and other fish species for nematodes was carried out mainly in the years 1947 to 1953. Fillets were examined on a candling table. Two varieties of nematodes were found: one, 94% in cod and 86% of the total in American plaice, witch flounder, haddock and redfish, was Porrocaecum, ranging between 15–16 and 57–58 mm. in length; the other, 6% in cod and 14% of the total for the other 4 fish species mentioned above, did not possess a caecum and had a longer pharynx than Porrocaecum relative to the total length and to the ventriculus length. The latter nematode was 17–18 to 33–34 mm. in length and resembled Anisakis but may possibly have been Eustoma.The infection level per 100 lb. (45 kg.) of cod fillets was lowest, 1 to 6 nematodes in ascending order, on Flemish Cap, the Grand Bank, the east coast of Newfoundland, off Labrador and southern St. Pierre Bank. It was highest, 223 nematodes, in the southern part of the Gulf of St. Lawrence. Intermediate values, 10 to 65 nematodes, were present in other areas. The nematode infection level in the larger American plaice was similar to that in cod, and infection per 100 lb. of fillets was especially heavy at the smaller sizes of plaice. Witch flounder, redfish and haddock showed low infection levels. Smelts living in the immediate neighbourhood of seal colonies were sometimes highly infected in terms of nematodes per 100 lb. of fillets. Nematodes were found in the fillets of the angler, Greenland cod, Greenland halibut, pollock, yellowtail flounder, longhorn sculpin and tomcod. It was concluded that the site of original infection of the fish was close to the site of deposition of nematode eggs by the seal host, and that the first intermediate hosts, invertebrates or small fish, were not very migratory.In the fillet, nematodes were most numerous in the thicker parts dorsal and posterior to the body cavity and less numerous in the thinner tail portion. The distribution fits the idea that nematodes emerging from the stomach of the fish enter the neighbouring body muscles.Of the seals which are the final hosts for Porrocaecum, harbour seals are common in Newfoundland areas where nematode infection of cod is high, as on the west coast of the island, but they are also especially numerous in southern Labrador where nematode infection of cod is low. The usual intermediate invertebrate or fish hosts may be scarce or lacking in Labrador and on the northeast coast of Newfoundland.It is concluded that the larger, browner, and more numerous Porrocaecum presents the problem of commercial importance, rather than the smaller, whiter Anisakis. The only practical biological attack in view at the moment is the reduction in numbers of harbour and grey seals, in the hope that the more numerous harp seal is not so important a final host as it at first sight appears to be in the Gulf of St. Lawrence. In many areas where harp seals are not present, or, where present, do not carry Porrocaecum, the harbour and grey seals appear to be the only final hosts of Porrocaecum. St. Mary's Bay, Newfoundland has many advantages as a site for a practical long-term experiment on reduction of nematode levels in cod flesh.

Diet composition of grey seals in the Gulf of St. Lawrence (Gulf) and around the coast of Newfoundland, Canada, was examined using identification of otoliths recovered from digestive tracts. Prey were recovered from 632 animals. Twenty-nine different prey taxa were identified. Grey seals sampled in the northern Gulf of St. Lawrence fed mainly on capelin, mackerel, wolffish and lumpfish during the spring, but consumed more cod, sandlance and winter flounder during late summer. Overall, the southern Gulf diet was more diverse, with sandlance, Atlantic cod, cunner, white hake and Atlantic herring dominating the diet. Capelin and winter flounder were the dominant prey in grey seals sampled from the east coast of Newfoundland, while Atlantic cod, flatfish and capelin were the most important prey from the south coast. Animals consumed prey with an average length of 20.4 cm (Range 4.2-99.2 cm). Capelin were the shortest prey (Mean = 13.9 cm, SE = 0.08, N = 1126), while wolffish were the longest with the largest fish having an estimated length of 99.2 cm (Mean = 59.4, SE = 2.8, N = 63). In the early 1990s most cod fisheries in Atlantic Canada were closed because of the collapse of the stocks. Since then they have shown limited sign of recovery. Diet samples from the west coast of Newfoundland indicate a decline in the contribution of cod to the diet from the pre-collapse to the postcollapse period, while samples from the southern Gulf indicate little change in the contribution of cod.

Lack of life history change in two over-exploited haddock (Melanogrammus aeglefinus) stocks

Factors influencing distribution of juvenile yellowtail flounder ( Limanda ferruginea) on the grand bank of Newfoundland

Geographically separated Atlantic cod (Gadus morhua) stocks in the northwest Atlantic exhibit life history variation and have been shown to differ genetically. The genetic and environmental contributions to phenotypic differences, however, have not yet been measured. We used common environment experiments to evaluate the importance of temperature on the observed growth variation between Grand Banks (GB) and Gulf of Maine (GOM) cod stocks. Larvae from the GB grew faster than GOM larvae at both 7 and 12°C. Growth rates of juveniles were not different, but GB juveniles had higher food conversion efficiencies than those from the GOM (at both ambient and warm temperatures). The results indicate that faster growth of GOM cod in the wild is not due to a higher genetic capacity for growth rate in GOM than in GB fish. The findings give evidence of genetically based phenotypic variation, which is in agreement with molecular studies on population differentiation in cod, and support the theory of countergradient variation in growth rates of larval fish.

We analyzed 47 yr (1946–92) of research trawl data and 5 yr (1964–68) of research gillnet data to identify spawning locations of Atlantic cod, Gadus morhua, in the Newfoundland–Labrador region. Offshore, spawners are common on the continental shelf but generally rare on the slope. Relative abundance of spawning individuals on the shelf is comparably high off northeast Newfoundland, within 100 km of the Newfoundland coast from Cape Freels to Cape Race, on central Grand Bank, and on St. Pierre Bank. Slope spawning is largely restricted to the eastern slope of Hamilton Bank, a small section of northern Grand Bank, and Flemish Cap. Inshore spawning is evident in southeastern Labrador and southeastern Newfoundland, particularly in St. Mary's, Placentia, Trinity, and Bonavista bays. Trajectories of satellite-tracked drifter buoys indicate that it is highly improbable that eggs spawned on the slope of Grand Bank and much of the northeastern Newfoundland slope will be transported into shelf and coastal waters. We conclude that cod spawn in areas in which their eggs and larvae are likely to be retained and that inshore spawning populations may provide a considerably larger contribution to cod recruitment in coastal Newfoundland than has previously been believed.

A study was initiated to ascertain the prevalence of a trypanosome in Atlantic cod (Gadus morhua) especially in relation to stocks in the Newfoundland area and as an aid in management and conservation. Highest prevalences were recorded in fish taken off the Labrador coast (ICNAF divisions 2J and 3K, 94 and 90%, respectively). Trypanosomes were not as prevalent in fish collected from the northern Grand Bank (46%, division 3L) or from the southern Grand Bank (13 and 16%, divisions 3N and 3O, respectively). A further decrease in prevalence occurred among fish collected on the Flemish Cap (10%,, division 3M) and St. Pierre Bank (8%, subdivision 3Ps), while the lowest levels (4%) were apparent in cod taken from the Gulf of St. Lawrence (divisions 4R and 4S). Fish sampled at inshore localities reflected prevalences corresponding to some extent to offshore localities. Cod taken on coastal Labrador and from northern Newfoundland have a high prevalence of trypanosome infections while in the more easterly bays, intermediate levels occur. A conspicuous decrease in prevalence was apparent in a sample taken from the most easterly inshore locality (Portugal Cove) and from two others on the south coast of Newfoundland. Lowest prevalences were noted among fish taken at four inshore localities in the Gulf of St. Lawrence. These results, based on prevalences of infection, support conclusions from other studies that there are at least six stocks of cod in the Newfoundland area with some degree of mixing.Key words: trypanosome, prevalence, cod stocks, Newfoundland–Labrador, ICNAF

Distribution of commercial flatfishes in the Newfoundland-Labrador region of the Canadian Northwest Atlantic and changes in certain biological parameters since exploitation

This paper describes the global mooring analysis conducted for the Terra Nova FPSO, located on the Grand Banks, offshore Eastern Newfoundland, Canada. The FPSO has a disconnectable internal turret mooring system that must withstand the 100-year storm environment, and be disconnectable to avoid collision with large icebergs. The global analysis of the FPSO vessel and mooring system focuses on the response of the system in storm conditions, and during offloading, disconnect and reconnect operations. The analysis was performed using sophisticated analytical and numerical techniques, integrated with a comprehensive model test program primarily for verification of the analysis. As the Terra Nova FPSO is the first such platform to operate in an iceberg region, a focus of the analysis was in studying the interaction of pack ice and icebergs with the FPSO system. The methodology used to analyze the FPSO system is outlined in this paper and some key results are presented. Introduction The Terra Nova FPSO will be located in approximately 95 meters water depth on the Grand Banks off the East Coast of Newfoundland, Canada. The region has a harsh environment, much like the Northern North Sea, with intense storms occurring frequently in winter. In addition, there is sea ice excursion into the region, including pack ice and icebergs. The FPSO system consists of a new-build FPSO vessel and a disconnectable turret with a thruster-assisted, 9-leg mooring system. The turret supports 14 risers and 5 umbilicals servicing wellheads in four or more glory holes. The internal turret mooring system has been designed to maintain station in the 100-year storm environment, and to be disconnectable to avoid an approaching iceberg on a collision course. Once the FPSO disconnects, the mooring and riser system is supported by a spider buoy that has an equilibrium depth of 35 meters below sea level. The global analysis of an FPSO system requires detailed knowledge of the environment, vessel characteristics, and the mooring system design. The analysis of the Terra Nova system has further complications due to the use of an automatically controlled thruster system to assist the mooring, and the disconnect and reconnect operations. The following sections briefly describe the methodology used to study the combined FPSO vessel and mooring system response, and present a few results to illustrate the performance of the system, and the accuracy of the analysis. Stationkeeping Design Basis The mooring system has been designed to meet or exceed the requirements of Lloyd's Register (References 1 and 2) for a thruster-assisted, permanent mooring system. The design basis for the FPSO global analysis is summarized below:The Terra Nova FPSO must be moored on station in a 100-year storm, requiring the turret mooring system to be designed for the 100-year environment. The mooring system can depend on the full capability of the thruster system (25 MW).In seastates up to the 1-year storm the mooring system can only utilize the heading control mode of the thruster system, with a maximum peak power demand of 10 MW.

Among highly migratory fish species, nursery areas occupied by juveniles often differ from adult habitats. To better understand the spatial dynamics of Canada's Northern cod stock, juveniles caught off the east coast of Newfoundland and Labrador were compared to adults from the same region as well as individuals from other areas in Atlantic Canada using double-digest restriction site-associated DNA sequencing-derived single nucleotide polymorphisms. A reduced proportion of homozygotes with a chromosomal inversion located in linkage group 1 (LG1) was detected between juvenile and adult samples in the Northern cod stock region, potentially indicating age-dependent habitat use or ontogenetic selection for attributes associated with the many genes located in LG1. No selectively neutral genetic differences were found between samples from the Northern cod stock; nevertheless, significant differences were found between some of these samples and cod collected from St. Pierre Bank, Bay of Fundy, Browns Bank and the southern Scotian Shelf. Clustering analysis of variants at neutral loci provided evidence for three major genetic units: (a) the Newfoundland Atlantic Coast, (b) eastern and southern Gulf of St. Lawrence and Burgeo Bank and (c) the Bay of Fundy, Browns Bank and southern Scotian Shelf. Both adaptive and neutral population structure within the Northern cod stock should be considered by managers to promote demographic rebuilding of the stock.

The Grand Banks off the coast of Newfoundland, Canada is home to several major offshore oil discoveries. Most notable are the 800+ MMbbl Hibernia and 400+ MMbbl Terra Nova fields, currently in production; the 200+ MMbbl White Rose field, currently under development towards planned start-up in early 2006; and the 500+ MMbbl Hebron field, whose development future is undetermined at this time. All discoveries are in a single producing basin, the Jeanne d'Arc. Since the discovery of Hibernia, there have been predictions that offshore Newfoundland could become the next North Sea. But while the Jeanne d'Arc Basin has proven to be a world-class producing basin, other large discoveries have remained elusive to date. Since the inception of the industry in the North Sea, thousands of exploration and delineation wells have been drilled and hundreds of fields have been developed. During a similar time period, well under 200 exploration or delineation wells have been drilled, and just two fields have entered production on the Grand Banks. While offshore Newfoundland and Labrador has not lived up to its early billing as the next North Sea, the opportunity remains for this region to be a more significant producing area, but probably not at the scale of the North Sea. Petro-Canada operates the Terra Nova field, and has substantial interests in Hibernia, White Rose, Hebron and all but one of the significant hydrocarbon discoveries in the region since 1979. This paper provides one perspective on the development of the Newfoundland offshore area - the considerable environmental, geological, technological and infrastructural challenges, the significant opportunities that are driving continued interest in the region, and the factors for success. Introduction The question being examined in this paper - whether the Grand Banks off the coast of Newfoundland and Labrador could be the next North Sea - has been asked almost since the first oil discovery at Hibernia in 1979. The four largest oil fields discovered to date - Hibernia, Terra Nova, White Rose and Hebron - are significant in terms of their reserves. In addition, there are 14 other smaller hydrocarbon discoveries - not individually commercial at present - some of which could potentially be tied into existing field developments at some future time. These discoveries established the Jeanne d'Arc Basin as a world class basin. This is where the development focus has been directed, with two fields in production - Hibernia and Terra Nova - and a third, White Rose, under development toward production start in early 2006. But success beyond the Jeanne d'Arc has not yet materialized. During a similar period, more than 250 fields have been developed in the North Sea, but this is on the strength of approximately 4000 exploration or delineation wells, compared with less than 200 offshore Newfoundland. There is undoubtedly more that can be done to maximize the potential of the Newfoundland offshore region. At the same time, perhaps some expectations have been unrealistic.

The peak spawning period of American plaice was the first part of April for Flemish Cap and ranged from the end of April for the Grand Bank and surrounding areas to the first part of June for Labrador–Northeast Newfoundland Shelf. Average bottom temperatures during spawning ranged from about 3.5 C for Flemish Cap and the deep spawning areas to the north, to about −1.3 C for St. Mary's Bay and the northern half of the Grand Bank. For the Southeast Grand Bank, Southwest Grand Bank, and St. Pierre Bank average spawning temperatures were 1.1, 2.8, and 2.7 C, respectively.There was evidence that some older, larger fish spawned first and also that plaice in deep water spawned later than those from shallower depths. At the latter depths light was a possible factor.According to samples from St. Mary's Bay the development of the sex products for spring spawning was apparently controlled by water temperatures during the previous fall and late summer.Fifty per cent of the females from Flemish Cap were mature at 7.8 years, the bottom temperature being almost constant at 3.5 C. For other areas the number of years ranged from 12.2 for the Southwest Grand Bank, with prevalent temperatures 0–3, to 15.2 C for St. Mary's Bay where temperatures were −1 to 1.0 C. For males the range was from 5.3 years for the Southeast Grand Bank to 7.5 years for St. Pierre Bank, no data being available for Flemish Cap.