Multiyear homing of Atlantic cod to a spawning ground

2001 ◽  
Vol 58 (12) ◽  
pp. 2325-2329 ◽  
Author(s):  
D Robichaud ◽  
G A Rose
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spawning Season ◽  
Spawning Ground ◽  
Long Distance ◽  
Tag Loss ◽  
Sea Bed ◽  
Placentia Bay

Long-term sonar transmitting tags were implanted in 27 female and 21 male cod (Gadus morhua) at the Bar Haven spawning ground in Placentia Bay, Newfoundland, in April 1998. Two thirds of tagged fish were relocated. All relocations during the 1999 and 2000 spawning seasons were within 10 km of the tagging site, the majority being within a few hundred metres. No tagged fish were relocated at other spawning grounds or elsewhere in the bay during the spawning season. Outside the spawning season, several tagged fish were relocated in other parts of the bay at ranges of a few kilometres to 110 km from the tagging site, as were 13 of 15 fishery returns (2 returns from several hundred kilometres outside the bay). Homing rates in 1999 and 2000 were 39% and 53%, respectively, after adjustments for tag loss, mortality, misreporting, and relocation efficiency based on returns from a sea-bed beacon tag left at the Bar Haven grounds. Multiyear homing was observed in 26% of cod. This study provides the first direct evidence that cod undertaking long-distance feeding migrations may home to a specific spawning ground in consecutive years, and a hypothesis for the slow recolonisation rates observed in North Atlantic cod stocks.

scholarly journals Home range and elevated egg densities within an inshore spawning ground of coastal cod

2007 ◽  
Vol 64 (5) ◽  
pp. 920-928 ◽  
Author(s):  
Sigurd Heiberg Espeland ◽  
Ailin Fernløf Gundersen ◽  
Esben Moland Olsen ◽  
Halvor Knutsen ◽  
Jakob Gjøsæter ◽  
...  
Keyword(s):  
Home Range ◽  
Site Fidelity ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Generalized Additive Models ◽  
Spatial Dynamics ◽  
Additive Models ◽  
Spawning Season ◽  
Spawning Ground ◽  
Spawning Site

Abstract Espeland, S. H., Gundersen, A. F., Olsen, E. M., Knutsen, H., Gjøsæter, J., and Stenseth, N. C. 2007. Home range and elevated egg densities within an inshore spawning ground of coastal cod. – ICES Journal of Marine Science, 64: 920–928. Atlantic cod (Gadus morhua) along the Norwegian Skagerrak coast are structured into genetically distinct local populations. Mechanisms contributing to this genetic structure may include spawning site fidelity of adult cod as well as retention of pelagic early life stages close to the spawning grounds. Spawning in sheltered inshore localities is likely to favour retention of eggs and larvae, the opposite situation to offshore spawning. A combined study was made of area utilization by adult cod and the distribution of cod eggs within an inshore locality of the Norwegian Skagerrak coast. The behaviour of adult cod was studied using acoustic telemetry and kernel modelling, and eggs were sampled throughout the spawning season. Generalized additive models were applied to test hypotheses about the spatial dynamics of the eggs, and the best model described a central spawning area that retained its integrity through time. Adult cod were confined to small parts of the study area and remained there throughout the spawning season. The average home range of the adult cod was 27 ha. Overall, the study demonstrated two mechanisms by which coastal (i.e. inshore) cod maintain their population structure: spawning site fidelity and the spatial dynamics of their eggs.

Influence of climatic changes on the parasites of Atlantic cod Gadus morhua off coastal Labrador, Canada

2006 ◽  
Vol 80 (2) ◽  
pp. 193-197 ◽  
Author(s):  
R.A. Khan ◽  
C.V. Chandra
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Age Groups ◽  
Climatic Conditions ◽  
Otter Trawl ◽  
Commercial Fishery ◽  
Metazoan Parasites ◽  
Mean Values ◽  
The North

AbstractA study was conducted in 2000 and 2003, following the collapse of the commercial fishery in 1990, to compare metazoan parasites of Atlantic cod Gadus morhua, captured off coastal Labrador, with samples taken in 1980 and 1986. Fish were captured by otter trawl offshore in the North Atlantic Fish Organisation subarea 2J. Parasites were removed from the digestive tract, stained, identified and compared between the different groups. Both the prevalence and mean abundance of trematodes, larval nematodes and E. gadi were significantly lower in fish taken in 2000 and 2003 than in 1980. While mean values of trematodes and nematodes declined in 1986, those of Echinorhynchus gadi remained unchanged in 1986 and 1990. Four-year-old cod sampled in 1990 harboured significantly fewer E. gadi than older age groups. The most commonly occurring trematodes included Podocotylereflexa, Lepidapedon elongatum, Derogenes varicus and Hemiurus levinseni while the larval nematode, Anisakis sp. was predominant. Comparison of offshore samples taken in 2000 and 2003 with others taken in previous years suggests an overall decline of parasites coincident with a change in climatic conditions, the absence of a major food source, namely capelin Mallotus villosus, of cod and ultimately the decline of the Labrador population.

Fish Catches and Long-Term Tidal Cycles in Northwest Atlantic Fisheries: A Nonlinear Regression Approach

1987 ◽  
Vol 44 (11) ◽  
pp. 1890-1897 ◽  
Author(s):  
Paul Cabilio ◽  
David L. DeWolfe ◽  
Graham R. Daborn
Keyword(s):  
New England ◽  
Nonlinear Regression ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Significant Negative Correlation ◽  
Clupea Harengus ◽  
Atlantic Menhaden ◽  
Melanogrammus Aeglefinus ◽  
Grand Banks

Selected long-term fisheries catch data from the New England – Fundy area and the Grand Banks were examined for concordance between changes in fish catches and the 18.6-yr nodal cycle of the tides using a nonlinear regression model. Significant positive correlations were found for Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), alewife (Alosa pseudoharengus), Atlantic herring (Clupea harengus harengus), and scallop (Placopecten magellanicus), with lag times that are biologically appropriate for the time from hatching to recruitment into the fishery. A significant negative correlation with the nodal cycle was evident for Atlantic menhaden (Brevoortia tyrannus), for which this area constitutes the most northerly part of its range. Cod catches on the Grand Banks showed no correlation with the nodal cycle. It is suggested that the correlations between the nodal cycle and the changes in fish catches are caused by correlated changes either in sea surface temperature or in productivity resulting from changes in the degree of vertical mixing.

scholarly journals Bacterial composition and succession during storage of North-Atlantic cod (Gadus morhua) at superchilled temperatures

2009 ◽  
Vol 9 (1) ◽  
pp. 250 ◽  
Author(s):  
Eyjólfur Reynisson ◽  
Hélène L Lauzon ◽  
Hannes Magnússon ◽  
Rósa Jónsdóttir ◽  
Guðrún Ólafsdóttir ◽  
...  
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Bacterial Composition

Intergenerational valuation of fisheries resources can justify long-term conservation: a case study in Atlantic cod (Gadus morhua)

2005 ◽  
Vol 62 (5) ◽  
pp. 1104-1110 ◽  
Author(s):  
C H Ainsworth ◽  
U R Sumaila
Keyword(s):  
Discount Rate ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Ecosystem Model ◽  
Conventional Model ◽  
Fisheries Resources ◽  
Optimal Harvest ◽  
Harvest Policies

Where the conventional model of discounting advocates aggressive harvest policies, intergenerational discounting could have been used to render the historic gross overfishing of Atlantic cod (Gadus morhua) economically unappealing compared with a more conservative long-term strategy. Under these discounting approaches, we compare the historic harvest trend from 1985 (and projected postcollapse earnings) with theoretical optimal harvest profiles determined by an ecosystem model. The optimal scenarios generate less initial harvest than the historic profile but maintain the resource and provide greater yields over the long term. At a discount rate equal to market interest, we demonstrate that it was more economic under conventional valuation to harvest the cod stock to collapse than it would have been to sustain the population. However, under intergenerational valuation, the sustainable optimal scenarios outperform the actual harvest profile. Application of conventional discounting by fishing consortiums may be partly to blame for depletion, yet management fell short of even that ideal.

scholarly journals Otolith chemistry and redistributions of Northern cod: evidence of Smith Sound – Bonavista Corridor connectivity

2018 ◽  
Vol 75 (12) ◽  
pp. 2302-2312 ◽  
Author(s):  
Victoria Neville ◽  
George Rose ◽  
Sherrylynn Rowe ◽  
Robyn Jamieson ◽  
Glenn Piercey
Keyword(s):  
Oxygen Isotope ◽  
Gadus Morhua ◽  
Direct Evidence ◽  
Atlantic Cod ◽  
Otolith Chemistry ◽  
Stable Oxygen Isotope ◽  
Metapopulation Structure ◽  
Northern Cod ◽  
Stable Oxygen ◽  
Placentia Bay

Stable oxygen isotope assays of otoliths (δ18Ooto) from migrant Atlantic cod (Gadus morhua Linnaeus, 1758) that overwintered in Smith Sound, Newfoundland, during 1995–2006 differed from those of nonmigrating summer residents and cod from Placentia Bay and Halibut Channel but did not differ from those of cod from the adjacent offshore Bonavista Corridor in summer. All fish sampled were of the 1990 year class (founder of the Smith Sound aggregation) at ages 8–10 years. Hence, overwintering Smith Sound and summering Bonavista Corridor cod likely experienced similar temperatures and salinities in each year of life, representing different migration stages of an intermixed group. Moreover, predictions of δ18Ooto from near-bottom ocean temperatures and salinities differed between inshore and offshore sites and, in general, matched observed signatures of inshore and offshore cod. The Bonavista Corridor cod, however, were an exception, having δ18Ooto signatures suggestive of inshore exposure. Our findings provide direct evidence of metapopulation structure in the Northern cod and are consistent with offshore rebuilding having been spurred by dispersal of cod from inshore Smith Sound.

Short- and long-term effects of fish density and specific water flow on the welfare of Atlantic cod, Gadus morhua

Aquaculture ◽  
2011 ◽  
Vol 322-323 ◽  
pp. 184-190 ◽  
Author(s):  
Børge Damsgård ◽  
Frode Bjørklund ◽  
Helge K. Johnsen ◽  
Hilde Toften
Keyword(s):  
Water Flow ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fish Density ◽  
Long Term Effects ◽  
Short And Long Term

Reproductive interactions between fugitive farmed and wild Atlantic cod (Gadus morhua) in the field

2010 ◽  
Vol 67 (8) ◽  
pp. 1221-1231 ◽  
Author(s):  
Justin J. Meager ◽  
Jon Egil Skjæraasen ◽  
Anders Fernö ◽  
Svein Løkkeborg
Keyword(s):  
Mating System ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spatial Dynamics ◽  
Wild Fish ◽  
Spawning Ground ◽  
Males And Females ◽  
Farmed Escapees ◽  
Ultrasonic Transmitters

Atlantic cod ( Gadus morhua ) are being increasingly farmed in net pens adjacent to coastal populations that are currently at historic lows. One concern is that farmed escapees enter local spawning shoals and mate with wild cod. We tested for the potential of escaped farmed cod to interact and hybridize with wild fish by examining the spatial dynamics of, and associations between, fish tagged with ultrasonic transmitters. Based on these data, we also investigated the basic mating system of cod in the field. The spawning ground was best described as a lekking arena. Wild males aggregated near the seafloor and associations between individuals were frequent. Wild females had a pelagic and dispersed distribution and rarely associated with each other. Associations between individual wild males and females were also infrequent. Farmed males rarely associated with wild fish and had core usage areas above the wild males, suggesting that they were not admitted into the spawning arena. Farmed females were over the spawning arena more frequently than wild females and often associated with wild males at the depth of the spawning arena, indicating potential mating with wild males and the possibility of courtship interference. Hence, hybridization between escaped farmed and wild cod is likely.

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