Reporting and shedding rate estimates from tag-recovery experiments on Atlantic cod (Gadus morhua) in coastal Newfoundland

2006 ◽  
Vol 63 (9) ◽  
pp. 1944-1958 ◽  
Author(s):  
Noel G Cadigan ◽  
John Brattey
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Mortality Rates ◽  
First Year ◽  
Commercial Fisheries ◽  
Dorsal Fin ◽  
Temporal And Spatial Variability ◽  
Temporal And Spatial ◽  
Reporting Rates ◽  
Tag Shedding

It is important to have good estimates of tag reporting rates when inferring exploitation rates and other mortality rates from tagging experiments. We estimate the reporting rates of single- and double-tagged Atlantic cod (Gadus morhua) caught in commercial fisheries around coastal Newfoundland, Canada, based on an extensive series of multi-reward tagging experiments conducted during 1997–2004. Reporting rates for single-tagged cod varied from 58% to almost 100%, with significant temporal and spatial variability. The odds of reporting a double-tagged cod was almost double that of a single-tagged cod. Returns from double-tagged cod allow us to estimate tag shedding rates. Tag shedding rates suggested that 22% of fish lost their tag during their first year at liberty; subsequently, tag shedding rates were much lower (<10%). We also found that twice as many fish lost tags when the tags were attached anteriorly at the base of the first dorsal fin compared with a position more towards the posterior end.

Spatiotemporal variations in juvenile mortality and cohort strength of Atlantic cod (Gadus morhua) off Newfoundland and Labrador

2020 ◽  
Vol 77 (3) ◽  
pp. 625-635
Author(s):  
Fan Zhang ◽  
Rick M. Rideout ◽  
Noel G. Cadigan
Keyword(s):  
Newfoundland And Labrador ◽  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Survival Rates ◽  
Mortality Rates ◽  
Spatiotemporal Variations ◽  
Juvenile Mortality ◽  
Modelling Framework ◽  
Fish Recruitment

Juvenile mortality is an important factor affecting the spatiotemporal dynamics of fish recruitment, but estimation of the spatiotemporal variations in juvenile mortality rates remains challenging. We developed a state-space metapopulation dynamics model to simultaneously estimate spatiotemporal variations in juvenile mortality rates and cohort strength and applied this general modelling framework to data from multiple surveys for juvenile (ages 2–5) Atlantic cod (Gadus morhua) stocks off Newfoundland and Labrador (NL). We found large-scale synchronized dynamics of decreasing juvenile mortality rates and increasing cohort strength from offshore surveys off eastern and southeastern NL, suggesting improving reproduction and survival rates for juvenile cod. No synchronized patterns of juvenile mortality rates and cohort strength were detected for cod stocks off southern and western NL, indicating more complex cod population spatial structures in those areas. Our study demonstrates the potential of juvenile mortality to cause temporally variable and spatially synchronized dynamics of fish recruitment, and the spatial patterns of juvenile mortality and cohort strength indicate some potential mismatch between cod population structure and current management units off NL.

Dispersal of wild and escapee farmed Atlantic cod (Gadus morhua) in Newfoundland

2013 ◽  
Vol 70 (5) ◽  
pp. 747-755 ◽  
Author(s):  
Emily W. Zimmermann ◽  
Craig F. Purchase ◽  
Ian A. Fleming ◽  
John Brattey
Keyword(s):  
Acoustic Telemetry ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Wild Fish ◽  
Spatiotemporal Distribution ◽  
Small Scale ◽  
Commercial Fisheries ◽  
Wild Populations ◽  
Ecological Consequences ◽  
Considerable Distance

Inherent trait differences and changes that arise through domestication could be maladaptive and lead to negative ecological consequences when non-native individuals escape from aquaculture cages and interact with wild populations. We used acoustic telemetry to map the spatiotemporal distribution of local wild (n = 29) and “escapee” farmed Atlantic cod (Gadus morhua) (n = 52) through experimental releases off eastern Newfoundland to determine the potential for interaction. Dispersal from the cage (>600 m) was rapid (50% dispersal: 12 h for farmed; 5 h for wild) and nonrandom. Most cod (85% farmed, 55% wild) moved northward, remaining close to shore. Although recaptures of escapees during small-scale recreational and commercial fisheries was high (11% farmed; 10% wild), our results suggest that directed efforts to recapture escapees would be logistically challenging. Cod migrated a considerable distance (maximum 256 km for wild; 157 km for farmed), and some returned to the bay the following year. The similarity of the distribution of escapee farmed and wild cod suggests the potential for interactions between farmed and wild fish, highlighting the importance of minimizing escapes.

Fishery and Biology of Atlantic Cod (Gadus morhua) off the Southwest Coast of Newfoundland

1969 ◽  
Vol 26 (12) ◽  
pp. 3133-3164 ◽  
Author(s):  
Allenby T. Pinhorn
Keyword(s):  
Growth Rates ◽  
Food Supply ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Total Mortality ◽  
Mortality Rates ◽  
Limited Data ◽  
Southwest Coast

Data collected from the fishery off the southwest coast of Newfoundland indicated a decrease in the proportions of larger and older cod in ICNAF Division 3Pn in recent years. Changes in total mortality rates in 3Pn and on Burgeo Bank have been attributed to fluctuations in total landings and effort. Decreased growth rates for the younger cod and increased followed by decreased growth for the older cod were attributed to increased food supply superimposed on decreased bottom temperatures. Cod from Burgeo Bank grow faster than those from 3Pn. Sizes caught by various types of inshore boats were similar but larger fish were caught in deeper water, in eastern rather than western localities, and in the latter part of the season. Peak spawning occurs in May. Males were predominant in longline catches and matured at an earlier age and smaller size than females. Fish in the 3Pn area matured earlier and at a smaller size than Burgeo Bank fish. Vertebral averages at different localities in the area were similar but averages have decreased in recent years. Limited data on weights and fecundity are presented. Results are discussed in light of the separation of West Newfoundland and Burgeo Bank stocks.

scholarly journals Growth, survival, diet, and on-growing husbandry of haddock Melanogrammus aeglefinus in tanks and netpens

2006 ◽  
Vol 63 (2) ◽  
pp. 376-384 ◽  
Author(s):  
James W. Treasurer ◽  
Harald Sveier ◽  
Warren Harvey ◽  
Roddy Allen ◽  
Christopher J. Cutts ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Vibrio Anguillarum ◽  
Dietary Lipid ◽  
Whole Body ◽  
Melanogrammus Aeglefinus ◽  
Hepatosomatic Index ◽  
First Year ◽  
Starvation Period ◽  
Haddock Melanogrammus Aeglefinus

Abstract Growth of haddock (Melanogrammus aeglefinus) was assessed in onshore tanks in West Scotland. Fish were stocked at a mean weight of 15 g in July 2002, with a second stocking in October 2002 at 25 g. Fish had a mean weight of 755 ± 150 (s.d.) g at 20 months after stocking and were harvested. The specific growth rate of haddock was similar to Atlantic cod (Gadus morhua) during the first year but decreased by 20% after that. Liver biomass was 17.6% of the whole body weight, suggesting haddock had difficulty in utilizing dietary lipid. Reduced lipid levels in the diet had only a short-term effect on hepatosomatic index (HSI). Haddock that were held under 24-h light from the first summer solstice did not mature at an age of two years when compared with complete maturation of fish reared under ambient light. Mortality during the on-growing stage was high (28% of stock) and was attributed to Vibrio anguillarum infection, and possibly to enlarged livers. An assessment of quality found taste and texture to be as good or equal to wild North Sea haddock, and quality was improved with a five-day starvation period. Haddock mean weight, six months after transfer to netpens, was not significantly different from that of fish of the same age grown in tanks.

Early Stages in the Recovery to Injury in the Dorsal Fin of the Atlantic Cod (Gadus morhua)

1964 ◽  
Vol 21 (2) ◽  
pp. 347-354
Author(s):  
P. M. Townsley ◽  
M. L. Hughes
Keyword(s):  
Gadus Morhua ◽  
Wound Closure ◽  
Atlantic Cod ◽  
Epidermal Cells ◽  
Dorsal Fin ◽  
Early Stages ◽  
Close Proximity ◽  
Cell Mitosis

The early stages in the recovery of the dorsal fin of the Atlantic cod (Gadus morhua) to a "clean cut injury" are described. It is concluded that the observed rapid epidermal migration, wound closure and cell mitosis are essentially the same in in-vivo as in in-vitro experiments. An accumulation of carbohydrate material occurs in the outermost layer of epidermal cells. There is a change in the carbohydrate composition or structure in the dermal layers at the site of injury. The basal epidermal cells rapidly divide in the in-vitro culture whereas only those basal epidermal cells in an in-vivo injury in close proximity to the injury divide. The surrounding nutrient medium in in-vitro cultures does not appear to be involved in the initial cell migration. However, ascorbic acid does stimulate epidermal migration, mucous secretion, and basal epidermal cell mitosis.

Estimating the relative roles of dispersion and predation in generating regional differences in mortality rates of larval radiated shanny (Ulvaria subbifurcata)

2002 ◽  
Vol 59 (1) ◽  
pp. 105-114 ◽  
Author(s):  
P Pepin ◽  
J F Dower ◽  
J A Helbig ◽  
W C Leggett
Keyword(s):  
Regional Differences ◽  
Mortality Rates ◽  
Pelagic Fish ◽  
Surface Currents ◽  
Multidisciplinary Study ◽  
Temporal And Spatial Variability ◽  
Local Abundance ◽  
Capelin Mallotus Villosus ◽  
Predator Interactions ◽  
Temporal And Spatial

We followed three patches of larval radiated shanny (Ulvaria subbifurcata) using drogued drifters to assess regional differences in growth and mortality rates. We estimate dispersive losses directly using local surveys of surface currents corrected for the tidally induced divergence caused by the lack of synopticity of our surveys. We also monitored the abundance of juvenile capelin (Mallotus villosus), the major planktivore in the region, using hydroacoustic integration. The pattern of divergence–convergence showed considerable temporal and spatial variability, which resulted in substantial changes in the inferred biological mortality rates. The net mortality rates appeared to be directly proportional to the local abundance of pelagic fish. As with other patch studies, we are limited in the number of observations we obtained, but the results of this multidisciplinary study do suggest a strong potential for prey–predator interactions between larvae and adult planktivorous fish.

Analysis of the Biological and Demographic Parameters of Northern Sand Lance, Ammodytes dubius, from the Newfoundland Grand Bank

1983 ◽  
Vol 40 (4) ◽  
pp. 409-419 ◽  
Author(s):  
G. H. Winters
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Mortality Rates ◽  
Demographic Parameters ◽  
Natural Mortality ◽  
Sand Lance ◽  
Temperature Variations ◽  
Grand Banks ◽  
The 1960S ◽  
Bank Sand

Biological characteristics and population dynamics of northern sand lance (Ammodytes dubius) population on the Grand Banks were investigated in the period 1968–79. Sand lance were distributed mainly in the shallower areas of the Grand Banks, particularly in the northeast and southeast areas. Through an examination of reproduction parameters I conclude that spawning occurs principally during the period November–January. Growth rates of Grand Bank sand lance are within the range of those described for the Scotian Shelf and are well correlated with temperature variations. Abundance indices, derived from groundfish surveys, indicate a substantial increase in abundance since the 1960s, and this increase is attributable to increased recruitment and reduced natural mortality. From correlation analyses I suggest that the decline in the Grand Bank population of Atlantic cod (Gadus morhua) may be responsible for the reduced mortality rates and increased abundance of Grand Bank sand lance during the 1970s.

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