Harvest Pressure on Coastal Atlantic Cod (Gadus morhua) from Recreational Fishing Relative to Commercial Fishing Assessed from Tag-Recovery Data

The influence of a lower condition on reproductive investment, somatic energy losses, and postspawning condition of Atlantic cod (Gadus morhua) was examined under the hypothesis that females, in response to lower available energy reserves, would reduce reproductive investment in order to limit somatic energy losses. Laboratory experiments revealed that female cod with high prespawning condition factors ended reproduction in better condition than females with low prespawning condition factors. Fecundity and total egg dry weight were significantly lower in poor-condition females. The loss in somatic mass and energy in these poor-condition females was nevertheless higher, in relative terms, than the losses experienced by females in good condition. Consequently, energy reserves invested in reproduction by poor-condition females increase their risk of mortality. In the northern Gulf of St. Lawrence during the early 1990s, reproductive females had lower fecundities and were in worse prespawning and postspawning condition. The condition of spent females suggested a greater impact of changes in environmental conditions on adult than on immature cod. Reproductive potential and possibly recruitment may have suffered from that situation and could have contributed to the failure of that stock to recover despite the moratorium on commercial fishing.

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Why the Atlantic cod (Gadus morhua) stock off eastern Nova Scotia has not recovered

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f01-095 ◽

2001 ◽

Vol 58 (8) ◽

pp. 1613-1623 ◽

Cited By ~ 46

Author(s):

Caihong Fu ◽

Robert Mohn ◽

L Paul Fanning

Keyword(s):

Nova Scotia ◽

Gadus Morhua ◽

Atlantic Cod ◽

Commercial Fishing ◽

Sudden Increase ◽

Annual Variations ◽

Structured Population ◽

Population Dynamics Model ◽

Structured Population Dynamics ◽

Age Structured

An age-structured population dynamics model, incorporating interactions between Atlantic cod (Gadus morhua), the fishery, and the grey seal (Halichoerus grypus) population, was applied to the cod stock off eastern Nova Scotia (Northwest Atlantic Fisheries Organization Divisions 4Vs and 4W, commonly abbreviated to 4VsW), a stock that has dramatically declined since the late 1980s. Mortality was modeled as having three components: fishing mortality (F), seal predation (Mp), and all other sources of natural mortality (M). Specifically, M was assumed to be distinct for immature cod (ages 14; Mi) and mature cod (age 5 and older; Mm), and respective annual variations were estimated. Parameters estimated also included recruitment (cod abundance at age 1; R), F, and Mp. Based on our estimates of F, Mp, and M, it is unlikely that the collapse of the 4VsW cod stock can be attributed to a sudden increase in M; fishing appears to have been the primary cause for the stock's decline. However, after the moratorium on commercial fishing in 1993, increasing Mp and Mm and low R may have contributed to the failure of the 4VsW cod stock to recover.

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Assessing changes in age and size at maturation in collapsing populations of Atlantic cod (Gadus morhua)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f05-065 ◽

2005 ◽

Vol 62 (4) ◽

pp. 811-823 ◽

Cited By ~ 151

Author(s):

Esben Moland Olsen ◽

George R Lilly ◽

Mikko Heino ◽

M Joanne Morgan ◽

John Brattey ◽

...

Keyword(s):

Genetic Variation ◽

Life Histories ◽

Gadus Morhua ◽

Atlantic Cod ◽

Reference Points ◽

Reaction Norms ◽

Commercial Fishing ◽

Evolutionary Changes ◽

Survival And Growth ◽

Maturation Age

By estimating probabilistic reaction norms for age and size at maturation, we show that maturation schedules of Atlantic cod (Gadus morhua) off Labrador and Newfoundland shifted toward earlier ages and smaller sizes during the late 1980s and early 1990s, when these populations underwent a severe collapse in biomass and subsequently were closed for directed commercial fishing. We also demonstrate that this trend towards maturation at younger ages and smaller sizes is halted and even shows signs of reversal during the closure of the fisheries. In addition, our analysis reveals that males tend to mature earlier and at a smaller size than females and that maturation age and size decrease with increasing latitude. Importantly, the maturation reaction norms presented here are robust to variation in survival and growth (through phenotypic plasticity) and are thus strongly indicative of rapid evolutionary changes in cod maturation as well as of spatial and sex-specific genetic variation. We therefore suggest that maturation reaction norms can provide helpful reference points for managing harvested populations with evolving life histories.

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Site Utilization by Atlantic Cod (Gadus morhua) in Off-Shore Gravel Habitat as Determined by Acoustic Telemetry: Implications for the Design of Marine Protected Areas

Marine Technology Society Journal ◽

10.4031/002533203787537401 ◽

2003 ◽

Vol 37 (1) ◽

pp. 27-34 ◽

Cited By ~ 10

Author(s):

James Lindholm ◽

Peter Auster

Keyword(s):

Protected Areas ◽

Marine Protected Areas ◽

Acoustic Telemetry ◽

Site Fidelity ◽

Gadus Morhua ◽

Atlantic Cod ◽

Commercial Fishing ◽

Individual Fish ◽

High Site ◽

Demersal Fishes

We quantified the site utilization of offshore gravel habitat by Atlantic cod (Gadus morhua) using acoustic telemetry. An omni-directional receiver was deployed inside Stellwagen Bank National Marine Sanctuary during Summer 2001 in an area that excluded commercial fishing for demersal fishes. Fish were collected using hook and line, tagged externally with coded acoustic pingers, and released on the seafloor using an “elevator” within the range of the receiver. Observations were made over 120 days. The total number of days that individual fish were recorded was up to 120 days and a total of 37% of all tagged fish showed high site fidelity to the study area.

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Occurrence of anisakid nematodes in Atlantic cod (Gadus morhua) and Greenland cod (Gadus ogac), West Greenland

Acta Parasitologica ◽

10.2478/s11686-010-0009-3 ◽

2010 ◽

Vol 55 (1) ◽

Cited By ~ 18

Author(s):

Kim Mouritsen ◽

Rasmus Hedeholm ◽

Henriette Schack ◽

Lone Møller ◽

Marie Storr-Paulsen ◽

...

Keyword(s):

Gadus Morhua ◽

Atlantic Cod ◽

Infection Intensity ◽

Stomach Contents ◽

Nematode Species ◽

Commercial Fishing ◽

Opposite Pattern ◽

West Greenland ◽

Pcr Rflp ◽

Anisakid Nematodes

AbstractAnisakid nematodes commonly infect gadids, and are of economic and aesthetic importance to the commercial fishing industry in Greenland as some species are pathogenic to humans. However, very little is known about the occurrence of these parasites and their impact on the hosts in Greenland waters. During a survey in 2005, stomach sample of 227 Atlantic cod (Gadus morhua) and 64 Greenland cod (Gadus ogac) was collected in Godthaab and Sisimiut fiord systems in West Greenland waters. All cod were dissected for stomach contents and anisakid nematodes were removed from the visceral cavity. Third stage larvae (L3) of three anisakid species were found, including Contracaecum osculatum (Rudolphi, 1802), Anisakis simplex (Rudolphi, 1809) and Hysterothylacium aduncum (Rudolphi, 1802). Molecular identification by PCR-RFLP indicated the presence of A. simplex s.s. and the sibling species C. osculatum B and C. The prevalence of infection by C. osculatum was higher in Greenland cod (84.3%) than in Atlantic cod (73.9%) whereas the prevalence of A. simplex showed an opposite pattern (Greenland cod 8.3%; Atlantic cod 24.2%). Only one G. morhua (1.0%) was infected by H. aduncum. No gender specific difference in both nematode species regarding prevalence of infection and mean infection intensity was evident, and there was no relationship between fish condition and the intensity of nematode infections. Standardised for size, capelin-eating cod were in better condition and more heavily infected than fish subsisting on alternative prey at the point of collection. Hence, nematode infections in the two gadids seem governed in part by feeding behaviour, and capelin appears a significant source of larval anisakids.

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Transition to an alternate state in a continental shelf ecosystem

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f04-079 ◽

2004 ◽

Vol 61 (4) ◽

pp. 505-510 ◽

Cited By ~ 96

Author(s):

Jae S Choi ◽

Kenneth T Frank ◽

William C Leggett ◽

Ken Drinkwater

Keyword(s):

Fish Species ◽

Gadus Morhua ◽

Atlantic Cod ◽

Demersal Fish ◽

Commercial Fishing ◽

Progressive Decline ◽

Ecological Changes ◽

Decadal Scale ◽

Flow Through

The collapse of Atlantic cod (Gadus morhua) stocks in the northwest Atlantic Ocean ranks among the most dramatic and widely known ecological changes of the 20th century. Less widely known are the systemic changes that occurred within these areas prior to and coincident with the cod collapse. Our analysis of a fishery-independent, long-term, standardized database collected on the eastern Scotian Shelf off Nova Scotia revealed that during the past four decades, coherent, community-level reductions in body size, biomass, and physiological condition have occurred in the resident demersal fish species. The changes occurred over large spatial (>104 km2) and short temporal (<10 years) scales, suggesting a progressive decline in the nature and extent of the energy flow through the benthic system. The unexpected and persistent poor condition of a variety of morphologically and functionally dissimilar demersal fish species, living in an environment of reduced intra- and inter-specific competition, suggests a decoupling of the benthic pelagic systems. This decoupling appears to be attributable to a cascading series of processes involving the cumulative removal of biomass resulting from commercial fishing, compensatory and self-stabilizing increases in pelagic fish biomass, and a decline in groundfish productivity exacerbated by decadal scale variability in water temperature and stratification.

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