The effects of isolation and colonization history on the genetic structure of marine-relict populations of Atlantic cod (Gadus morhua) in the Canadian Arctic

2006 ◽  
Vol 63 (8) ◽  
pp. 1830-1839 ◽  
Author(s):  
David C Hardie ◽  
Roxanne M Gillett ◽  
Jeffrey A Hutchings
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Allelic Diversity ◽  
Canadian Arctic ◽  
Environmental Stochasticity ◽  
Arctic Lakes ◽  
The Arctic ◽  
Effective Population ◽  
Eastern Canada ◽  
High Allelic Diversity

The genetic consequences of extended periods at low population size are fundamental to the conservation of depleted species such as the Atlantic cod (Gadus morhua). We compared microsatellite genetic variability among cod populations in Canadian Arctic lakes with that of Gilbert Bay resident and inshore cod from eastern Canada. The Arctic populations had the lowest genetic diversity and were the most strongly genetically structured and distinct. By contrast, eastern Canadian samples expressed high allelic diversity and were not significantly genetically structured or distinct relative to each other, whereas Gilbert Bay resident cod were intermediate to the Arctic and eastern Canadian groups. Our results are consistent with the hypothesis that the Arctic populations were colonized between 8000 and 5000 years ago and have experienced little or no gene flow since that time. Despite isolation at the extreme of the species' range, the Arctic populations have retained relatively high heterozygosities and high genetic effective population sizes relative to census sizes (Ne–Nc ratios). Potential explanations for this include the absence of fishing pressure, allowing for the persistence of large, highly fecund individuals, as well as biotic (e.g., absence of planktivores) and abiotic (e.g., low environmental stochasticity) factors in the Arctic lakes that minimize individual variance in reproductive success.

The Ecology of Atlantic Cod (Gadus morhua) in Canadian Arctic Lakes

ARCTIC ◽  
2011 ◽  
Vol 64 (2) ◽  
Author(s):  
David C. Hardie ◽  
Jeffrey A. Hutchings
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Canadian Arctic ◽  
Arctic Lakes

Large effective population size and temporal genetic stability in Atlantic cod (Gadus morhua) in the southern Gulf of St. Lawrence

2010 ◽  
Vol 67 (10) ◽  
pp. 1585-1595 ◽  
Author(s):  
Nina Overgaard Therkildsen ◽  
Einar Eg Nielsen ◽  
Douglas P. Swain ◽  
Jes Søe Pedersen
Keyword(s):  
Genetic Variability ◽  
Population Size ◽  
Effective Population Size ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Population Decline ◽  
Allelic Diversity ◽  
Estimation Methods ◽  
Effective Population ◽  
Commercial Fish

Worldwide, many commercial fish stocks have experienced dramatic declines due to overfishing. Such fisheries-induced population reductions could potentially erode the genetic diversity of marine fish populations. Based on analyses of DNA extracted from archived and contemporary samples, this paper compares the genetic variability at nine microsatellite loci in a Canadian population of Atlantic cod ( Gadus morhua ) over 80 years, spanning from before the fishery intensified to now when the population is at historically low abundance. Extensively validated genetic data from the temporally spaced samples were used to estimate the effective population size. Over the period, we observed no loss of either heterozygosity or allelic diversity. Several of the estimation methods applied could not distinguish the effective population size from infinity, and the lower 95% confidence limit on estimates was generally >500, suggesting that the effective population size is probably considerably larger than this. Hence, it appears that the southern Gulf of St. Lawrence cod stock has maintained genetic variability to sustain future evolution despite a dramatic population decline.

Automated monitoring of a large-scale cod (Gadus morhua) migration in the open sea

2002 ◽  
Vol 59 (12) ◽  
pp. 1845-1850 ◽  
Author(s):  
Luc A Comeau ◽  
Steven E Campana ◽  
Martin Castonguay
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Seasonal Migration ◽  
Migration Routes ◽  
Eastern Canada ◽  
Migration Patterns ◽  
Migration Timing ◽  
Open Sea ◽  
And Migration

The migration patterns of marine fishes are poorly known, in part owing to the technical limitations associated with tracking the movements of animals in deep water. Here we document a large-scale, directed, migration of Atlantic cod (Gadus morhua) off eastern Canada. Our approach was based on the acoustic tagging of 126 fish and the deployment of 69 subsurface receivers, stretching over a 160-km distance along the edge of the Laurentian Channel. After 1 year of automated recording, we found that 65% of the fish migrated out of coastal waters in two distinct runs during the summer–autumn period. The offshore-migrating fish overwintered in deep Laurentian Channel waters, returning inshore in April. Individual migration routes and migration timing were variable, indicating that the cod did not aggregate in large schools during the seasonal migration events.

scholarly journals Genomic testing of landlocked Kildin cod (Gadus morhua kildinensis) for its ancestral state: stationary or migratory ecotype?

2016 ◽  
Author(s):  
Anastasia A Teterina ◽  
Lev A Zhivotovsky
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Habitat Preferences ◽  
Genomic Testing ◽  
Ancestral State ◽  
Genome Diversity ◽  
Effective Population ◽  
Marine Population ◽  
Genomic Regions ◽  
Kildin Cod

Kildin cod is a small landlocked population of Atlantic cod reproductively isolated from marine counterparts for around 1500-2000 years. The Kildin cod lives in a shallow meromictic lake in the five-meter intermediate layer of water with sharp gradients of oxygen and salinity. The cod had an effective population size of around one hundred individuals and evolved unique physiological, morphological and behavioral features. The marine Atlantic cod has two ecologically distinct forms: the stationary (coastal) and migratory (deep-water) ecotypes that differ in migratory behavior and habitat preferences (the depth, oxygen content, salinity and temperature). To understand the origin and genetic properties of Kildin cod, we scrutinized genomic regions associated with the cod ecotypes differentiation (LG1, LG2, and LG7) and found out that Kildin cod’s regions LG2 and LG7 were fixed with the migratory variants, whereas polymorphic LG1 had a higher frequency of the stationary variant, that could be explained by the possible strong genetic drift. The lake cod investigated had four times lesser genome diversity than marine population. Our finding suggests that Kildin cod originated from the migratory ecotype of the marine cod.

Some ectoparasitic trichodinids from Atlantic cod, Gadus morhua L., with a description of Trichodina cooperi n.sp.

1989 ◽  
Vol 67 (7) ◽  
pp. 1793-1800 ◽  
Author(s):  
S. L. Poynton ◽  
J. Lom
Keyword(s):  
Nova Scotia ◽  
Body Surface ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Geographic Range ◽  
The Body ◽  
Wild Fish ◽  
Eastern Canada ◽  
Mean Diameter ◽  
The Mean

Trichodina murmanica Polyanskiy, 1955 (= Trichodina domerguei subsp. saintjohnsi Lom and Laird, 1969) and Trichodina cooperi n.sp. were commonly encountered on skin and fins of Atlantic cod, Gadus morhua L., near Halifax, Nova Scotia, Canada. A third species of Trichodina, probably new, was recorded from the skin of one fish. This is believed to be the first report of the genus Trichodina from the body surface of gadoid fish from eastern Canada, and the known geographic range of T. murmanica is extended. Trichodina cooperi n.sp. has an adoral ciliary spiral of 370–380° and is relatively large, the mean diameter of the body is 110 μm, of the adhesive disc (with dark center), 95 μm, and of the denticulate ring, 59 μm. The denticulate ring consists of 24–29 denticles (usually 27), with 7–9 radial pins per denticle. Each denticle has a broad blade, a large central part, and a slightly curved thorn of moderate to broad width, with a central rib when mature. The thorn is approximately twice the length of the blade. The horseshoe-shaped macronucleus has a diameter of 80.0 μm and the micronucleus is in the +y position. Trichodina spp. infected 26% of 39 wild fish 20 to < 60 cm long. Most wild fish yielded less than five ciliates per 24 × 50 mm smear.

Influence of growth and survival costs of reproduction on Atlantic cod, Gadus morhua, population growth rate

1999 ◽  
Vol 56 (9) ◽  
pp. 1612-1623 ◽  
Author(s):  
Jeffrey A Hutchings
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Environmental Stochasticity ◽  
Individual Growth ◽  
Growth And Survival ◽  
Individual Growth Rate ◽  
Age Structured ◽  
Reproductive Rates

A stochastic, age-structured life history model was used to examine how age at maturity (theta), pre- (Zimm) and postreproductive (Zmat) mortality, and postreproductive growth rate can affect maximum reproductive rates of fish at low population size. Simulations suggest that annual (r) and per-generation (R0) metrics of population growth for Newfoundland's northern Grand Bank Atlantic cod, Gadus morhua, are primarily influenced by changes to mortality prior to and following reproduction. At observed weights at age and Zmat = 0.2, r ranged between 0.135 and 0.164 for cod maturing at between 4 and 7 years. Incremental increases in either Zimm or Zmat of 0.1 were associated with 0.03-0.05 reductions in r. To effect similar reductions, individual growth rate would have to decline by approximately one half. At observed weights at age, increases in Zmat from 0.20 to 0.45 increased the probability of negative per-generation growth from 3 to 26% for cod maturing at 4 years and from 6 to 46% for cod maturing at 7 years. Thus, even in the absence of fishing mortality, little or no population growth by Atlantic cod may not be unexpected in the presence of environmental stochasticity, particularly when accompanied by increases in mortality and declining individual growth.

Nematode Infestation of Fillets from Atlantic Cod, Gadus morhua, off Eastern Canada

1988 ◽  
Vol 74 (6) ◽  
pp. 1038 ◽  
Author(s):  
C. V. Chandra ◽  
R. A. Khan
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Eastern Canada

Mixing and migration of overwintering Atlantic cod (Gadus morhua) stocks near the mouth of the Gulf of St. Lawrence

1999 ◽  
Vol 56 (10) ◽  
pp. 1873-1881 ◽  
Author(s):  
S E Campana ◽  
G A Chouinard ◽  
J M Hanson ◽  
A Fréchet
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fishing Effort ◽  
Trace Element Composition ◽  
Eastern Canada ◽  
Management Area ◽  
Elemental Fingerprint ◽  
And Migration ◽  
Southern Flank

Millions of Atlantic cod (Gadus morhua) migrate distances of up to 500 km each fall to aggregate together in a small overwintering area off eastern Canada. Synoptic research vessel surveys carried out each January between 1994 and 1997 documented dense aggregations of cod along both flanks of the Laurentian Channel in each year, with estimated biomasses exceeding 100 000 metric tons. Using the trace element composition of the otolith ("otolith elemental fingerprint") as a natural tag, we found members of four populations to be present on the overwintering grounds in significant numbers, yet large-scale mixing among the populations was minimal. Individual trawl samples were often composed of a single population, suggesting that population integrity was maintained at a scale of <20 km. Cod from the southern Gulf of St. Lawrence dominated the population composition along the southern flank of the Channel, while cod from the northern Gulf dominated the northern flank; the distributions of both of these populations extended well to the east of their summer habitats and were remarkably similar across years. There was no evidence of large-scale mixing across the Channel. In light of the substantive migration of northern Gulf cod into the management area for the southern Newfoundland population, fishing effort off southern Newfoundland has the potential to reduce the size of the northern Gulf population.

scholarly journals Genomic testing of landlocked Kildin cod (Gadus morhua kildinensis) for its ancestral state: stationary or migratory ecotype?

2016 ◽  
Author(s):  
Anastasia A Teterina ◽  
Lev A Zhivotovsky
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Habitat Preferences ◽  
Genomic Testing ◽  
Ancestral State ◽  
Genome Diversity ◽  
Effective Population ◽  
Marine Population ◽  
Genomic Regions ◽  
Kildin Cod

Kildin cod is a small landlocked population of Atlantic cod reproductively isolated from marine counterparts for around 1500-2000 years. The Kildin cod lives in a shallow meromictic lake in the five-meter intermediate layer of water with sharp gradients of oxygen and salinity. The cod had an effective population size of around one hundred individuals and evolved unique physiological, morphological and behavioral features. The marine Atlantic cod has two ecologically distinct forms: the stationary (coastal) and migratory (deep-water) ecotypes that differ in migratory behavior and habitat preferences (the depth, oxygen content, salinity and temperature). To understand the origin and genetic properties of Kildin cod, we scrutinized genomic regions associated with the cod ecotypes differentiation (LG1, LG2, and LG7) and found out that Kildin cod’s regions LG2 and LG7 were fixed with the migratory variants, whereas polymorphic LG1 had a higher frequency of the stationary variant, that could be explained by the possible strong genetic drift. The lake cod investigated had four times lesser genome diversity than marine population. Our finding suggests that Kildin cod originated from the migratory ecotype of the marine cod.

Larval Anisakis simplex (Nematoda: Ascaridoidea) Infection in the Musculature of Atlantic Cod, Gadus morhua, from Newfoundland and Labrador

1992 ◽  
Vol 49 (12) ◽  
pp. 2635-2647 ◽  
Author(s):  
John Brattey ◽  
Claude A. Bishop
Keyword(s):  
Newfoundland And Labrador ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Body Cavity ◽  
The Body ◽  
Anisakis Simplex ◽  
South Coast ◽  
The South ◽  
Eastern Canada ◽  
Examination Method

Larvae of Anisakis simplex were found in the flesh of Atlantic cod, Gadus morhua, collected in 21 regions around Newfoundland and Labrador during 1985–87. Prevalence and abundance increased with cod size and varied geographically; cod off Labrador had the fewest larvae whereas those from the south coast of Newfoundland were the most heavily infected. Most larvae (~95%) occurred in flesh surrounding the body cavity (napes), with a significantly higher percentage of the nematodes (~58%) in the flesh on the left side. In 505 cod in which all tissues were examined, 85.6, 10.8, and 3.5% of the A. simplex resided in the body cavity and viscera, napes, and fillets, respectively. Cod surveyed tended to have more A. simplex in the musculature than those from other areas off eastern Canada, but are lightly infected compared with most other Atlantic cod stocks. The examination method (candling combined with slicing) recovered, on average, 42% of the A. simplex present in the flesh; consequently, infection statistics reported here are underestimates. Numbers of A. simplex in cod off Labrador and eastern Newfoundland are similar to those observed during 1947–53, but the abundance of A. simplex appears to have increased among cod from NAFO Subdivision 3Pn.

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