Enhancing the reproductive potential of local populations of coastal Atlantic cod (Gadus morhua)

2002 ◽  
Vol 59 (10) ◽  
pp. 1685-1695 ◽  
Author(s):  
J S Wroblewski ◽  
H W Hiscock
Keyword(s):  
Gadus Morhua ◽  
Egg Quality ◽  
Atlantic Cod ◽  
Local Population ◽  
Reproductive Potential ◽  
Pseudopleuronectes Americanus ◽  
Farmed Fish ◽  
Potential Fecundity ◽  
Spawning Period ◽  
Natural Diet

We investigate the feasibility of enhancing the reproductive potential of northern Atlantic cod (Gadus morhua L.) populations resident in Newfoundland and Labrador bays by "catch, grow out, and release". This entails trapping juvenile and young adult fish from the local population, increasing their growth, maturation rate, and potential fecundity by feeding them a natural diet in net pens, and then returning the fish to their natal bay habitat to spawn. To determine whether multiyear farming affects spawning success, we determined the spawning period and egg quality of cod held in captivity for three growth seasons. Farmed cod spawned in a net pen concurrently with wild cod in Trinity Bay during 1995 and produced fertilized eggs from which viable larvae hatched. Sonic tracking showed that cod farmed for 3 years and then released reintegrated with wild cod aggregations over known spawning grounds. Recaptures of tagged fish several years after release suggest that farmed fish remained in the bay as members of the resident population. Fishing mortality (bycatch in coastal fisheries for lumpfish (Cyclopterus lumpus) and winter flounder (Pseudopleuronectes americanus)) of released farmed cod was not negligible, emphasizing that any enhancement effort must be carried out under a complete fishing moratorium.

Fecundity, Atresia, and Egg Size of Captive Atlantic Cod (Gadus morhua) in Relation to Proximate Body Composition

1991 ◽  
Vol 48 (12) ◽  
pp. 2333-2343 ◽  
Author(s):  
O. S. Kjesbu ◽  
J. Klungsøyr ◽  
H. Kryvi ◽  
P. R. Witthames ◽  
M. Greer Walker
Keyword(s):  
Gadus Morhua ◽  
White Muscle ◽  
Atlantic Cod ◽  
Dry Weight ◽  
Oocyte Diameter ◽  
Potential Fecundity ◽  
Spawning Period ◽  
The Mean ◽  
Egg Diameter ◽  
High Condition

Captive Atlantic cod (Gadus morhua) were fed at four ration levels (starvation, maintenance, moderate, and excess) for periods of 6–9 mo prior to and during spawning. At the end of the experiment, water, protein, glycogen, and fat contents of the liver, white muscle, and ovary were estimated. The depletion of the white muscle and liver was related to oocyte maturation and in particular to the proportion of eggs spawned (PES). The influx of protein into the ovary, the mean hydrated egg diameter, and the egg dry weight all reached maximum values at 10% PES and subsequently declined. Mean vitellogenic oocyte diameter was small prior to spawning but rose to a maximum at PES = 10%. Cod with high condition factors produced more previtellogenic oocytes and used a larger fraction during vitellogenesis. Actual fecundity of specimens deprived of food during the spawning period was between 20 and 80% of the potential fecundity depending on the nutritional status of the fish. Intensity of atresia in moderate ration fish increased from 0% at PES = 0% to 33% at PES = 80%. Estimates of durations of α-atretic vitellogenic oocytes varied between 10 and 13 d at 8 °C assuming a spawning period of 50 d.

scholarly journals Did population collapse influence individual fecundity of Northwest Atlantic cod?

2007 ◽  
Vol 64 (7) ◽  
pp. 1338-1347 ◽  
Author(s):  
J. C. Stares ◽  
R. M. Rideout ◽  
M. J. Morgan ◽  
J. Brattey
Keyword(s):  
Egg Production ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Reproductive Potential ◽  
Population Recovery ◽  
Potential Fecundity ◽  
Northwest Atlantic ◽  
Population Collapse ◽  
Variable Nature ◽  
Individual Fecundity

Abstract Stares, J. C., Rideout, R. M., Morgan, M. J., and Brattey, J. 2007. Did population collapse influence individual fecundity of Northwest Atlantic cod? – ICES Journal of Marine Science, 64:1338 –1347. We examined the influence of population collapse on individual potential fecundity and total population egg production (TEP) of three northwest Atlantic cod (Gadus morhua) populations: northern cod (Divisions 2J3KL), southern Grand Bank cod (NAFO Divisions 3NO), and southern Newfoundland cod (Subdivision 3Ps). Fecundity at length increased in conjunction with population collapse for two (3NO, 3Ps) of the three populations. Subsequent moderate population recovery between the 1990s and 2000s in 3Ps was accompanied by a decrease in fecundity at length. A large decrease in fecundity at length for 3NO during the same time period, despite little or no population recovery, coupled with the fact that there was no obvious difference in fish condition between the two time periods, suggested that density-independent factors could be contributing to the changes in fecundity. Use of pre-collapse fecundity–length relationships to estimate TEP in the post-collapse period resulted in underestimation of TEP by as much as 30% in 3NO and 46% in 3Ps, whereas in 2J3KL, TEP was overestimated by as much as 18%. Although the results do not fully support the hypothesis of an inverse relationship between population size and fecundity, they do demonstrate the variable nature of cod fecundity which, if not accounted for, can lead to erroneous perceptions of stock reproductive potential.

Spawning behaviour of Atlantic cod, Gadus morhua: evidence of mate competition and mate choice in a broadcast spawner

1999 ◽  
Vol 56 (1) ◽  
pp. 97-104 ◽  
Author(s):  
Jeffrey A Hutchings ◽  
Todd D Bishop ◽  
Carolyn R McGregor-Shaw
Keyword(s):  
Mate Choice ◽  
Gadus Morhua ◽  
Dna Analysis ◽  
Atlantic Cod ◽  
Multiple Paternity ◽  
Reproductive Behaviour ◽  
Male Dominance ◽  
Male Body ◽  
Experimental Conditions ◽  
Spawning Period

We quantified individual differences in Atlantic cod, Gadus morhua, reproductive behaviour at a field-reported spawning density under experimental conditions. Marked individuals (nine females, seven males) were observed twice daily and videotaped continuously for 9 weeks at ambient photoperiod and temperature in a large tank (60 m3). Agonistic interactions appeared to maintain a size-based dominance hierarchy among males. Multiple paternity per spawning bout, revealed by microsatellite DNA analysis, suggested a link between dominance and fertilization success. Interactions between sexes were dominated by the circling of females by males. Predicated by vertical separation from males, and after descending to the bottom, a motionless female would be circled up to 17 times, often by one male per circling bout but by several males throughout the spawning period. Although circling frequency increased with male dominance and male body size, initiation and termination of this behaviour appeared to be under female control. Circling provides opportunities for males to gain individual access to reproductive females and for females to assess the quality of potential mates. Our evidence for nonrandom mate choice and for male-male competition and display has implications for Atlantic cod mating systems and effects of fishing on their reproductive success.

scholarly journals Genetic identification of farmed and wild Atlantic cod, Gadus morhua, in coastal Norway

2011 ◽  
Vol 68 (5) ◽  
pp. 901-910 ◽  
Author(s):  
Kevin A. Glover ◽  
Geir Dahle ◽  
Knut E. Jørstad
Keyword(s):  
Case Studies ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Genetic Interactions ◽  
Genetic Identification ◽  
Fish Farms ◽  
Multiple Sources ◽  
Farmed Fish ◽  
Farmed Escapees

Abstract Glover, K. A., Dahle, G., and Jørstad, K. E. 2011. Genetic identification of farmed and wild Atlantic cod, Gadus morhua, in coastal Norway. – ICES Journal of Marine Science, 68: 901–910. Each year thousands of Atlantic cod escape from Norwegian fish farms. To investigate the potential for the genetic identification of farmed–escaped cod in the wild, three case studies were examined. Samples of farmed, recaptured farmed escapees, and wild cod were screened for ten microsatellite loci and the Pan I locus. Variable genetic differences were observed among cod sampled from different farms and cages (pairwise FST = 0.0–0.1), and in two of the case studies, the most likely farm(s) of origin for most of the recaptured escapees were identified. In case study 2, wild cod were genetically distinct from both farmed fish (pairwise FST = 0.026–0.06) and recaptured farmed–escaped cod (pairwise FST = 0.029 and 0.039), demonstrating the potential to detect genetic interactions in that fjord. Genetic identification of escapees was more challenging in case study 3, and some morphologically characterized wild cod were found to most likely represent farmed escapees. It is concluded that where cod are farmed in the same region as their own parents/grandparents were initially sourced, or where farmed escapees originate from multiple sources, quantifying genetic interactions with wild populations will be challenging with neutral or nearly neutral markers such as microsatellites.

Marine Fish Tissue Culture

1963 ◽  
Vol 20 (3) ◽  
pp. 679-684 ◽  
Author(s):  
P. M. Townsley ◽  
H. G. Wight ◽  
M. A. Scott
Keyword(s):  
Tissue Culture ◽  
Marine Fish ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
White Perch ◽  
Kidney Tissue ◽  
Fish Tissue ◽  
Pseudopleuronectes Americanus ◽  
Myoxocephalus Scorpius ◽  
Raja Radiata

Cell proliferation of tissue explants of different organs from marine fish has been achieved in a nutrient solution composed of Medium 199 plus 10% human serum. Fin, spleen, heart, kidney, liver, gonad, brain, uterus, and thymus tissues have been cultured. The tissues were obtained from sexually mature Atlantic cod (Gadus morhua), white perch (Roccus americanus) winter flounder (Pseudopleuronectes americanus), thorny skate (Raja radiata), American goosefish (Lophius americanus), pollock (Pollachius virens), and shorthorn sculpin (Myoxocephalus scorpius). An actively dividing cell culture of flounder kidney cells prepared by mechanical disruption of the kidney tissue was maintained through serial transfers over several months. Heart explants from the cod vigorously pulsated in tissue culture.

scholarly journals Systematic bias in estimates of reproductive potential of an Atlantic cod (Gadus morhua) stock: implications for stock–recruit theory and management

2006 ◽  
Vol 63 (5) ◽  
pp. 980-994 ◽  
Author(s):  
C Tara Marshall ◽  
Coby L Needle ◽  
Anders Thorsen ◽  
Olav Sigurd Kjesbu ◽  
Nathalia A Yaragina
Keyword(s):  
Egg Production ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Reproductive Potential ◽  
Threshold Level ◽  
Systematic Bias ◽  
Stock Status ◽  
Relative Fecundity ◽  
Time Period ◽  
Spawning Stock

Stock–recruit relationships that use spawning stock biomass (SSB) to represent reproductive potential assume that the proportion of SSB composed of females and the relative fecundity (number of eggs produced per unit mass) are both constant over time. To test these two assumptions, female-only spawner biomass (FSB) and total egg production (TEP) were estimated for the Northeast Arctic stock of Atlantic cod (Gadus morhua) over a 56-year time period. The proportion of females (FSB/SSB) varied between 24% and 68%, and the variation was systematic with length such that SSB became more female-biased as the mean length of spawners increased. Relative fecundity of the stock (TEP/SSB) varied between 115 and 355 eggs·g–1 and was significantly, positively correlated with mean length of spawners. Both FSB and TEP gave a different interpretation of the recruitment response to reductions in stock size (overcompensatory) compared with that obtained using SSB (either compensatory or depensatory). There was no difference between SSB and FSB in the assessment of stock status; however, in recent years (1980–2001) TEP fell below the threshold level at which recruitment becomes impaired more frequently than did SSB. This suggests that using SSB as a measure of stock reproductive potential could lead to overly optimistic assessments of stock status.

scholarly journals Differences in spawning time of captive Atlantic cod from four regions of Norway, kept under identical conditions

2006 ◽  
Vol 63 (2) ◽  
pp. 216-223 ◽  
Author(s):  
Håkon Otterå ◽  
Ann-Lisbeth Agnalt ◽  
Knut E. Jørstad
Keyword(s):  
Life History ◽  
Genetic Control ◽  
Environmental Conditions ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spawning Period ◽  
Life History Parameters ◽  
Wide Range ◽  
Spawning Time ◽  
The Difference

Abstract Several hundred Atlantic cod (Gadus morhua L.) were collected from selected spawning grounds along the Norwegian coast in March 2002. Four areas or regions that represent a wide range of environmental conditions were chosen for our breeding experiments: Porsangerfjord, Tysfjord, Helgeland, and Øygarden. Cod were transported to Øygarden near Bergen, individually tagged, and kept in sea cages. In both 2003 and 2004, a total of 40 family groups (adult pairs) representing the four regions were monitored for their spawning performance in separate tanks. During the spawning period, the quantity and diameter of eggs were recorded. During 2003, the time of peak spawning differed among groups. It was evident that the broodstock from the Øygarden region spawned about one month earlier than the broodstock collected from the Helgeland region. This also occurred in 2004, two years after the cod were collected, suggesting that the difference has a genetic component. Differences in life history parameters between cod populations, such as spawning cycles as described here, could be adaptive and under genetic control. This must be taken into consideration when assessing precautionary means of overcoming the problem with escapees from future cod mariculture.

Maternal age, fecundity, egg quality, and recruitment: linking stock structure to recruitment using an age-structured Ricker model

2012 ◽  
Vol 69 (10) ◽  
pp. 1631-1641 ◽  
Author(s):  
Andrew O. Shelton ◽  
Stephan B. Munch ◽  
David Keith ◽  
Marc Mangel
Keyword(s):  
Age Structure ◽  
Maternal Age ◽  
Gadus Morhua ◽  
Egg Quality ◽  
Atlantic Cod ◽  
Natural Populations ◽  
Ricker Model ◽  
Icelandic Population ◽  
Spawning Stock ◽  
Age Structured

Understanding the process of recruitment is fundamental to fisheries biology and management. However, recruitment in natural populations is highly variable and rarely well described by classical stock–recruitment relationships (SRRs). Recent analyses suggest that the age composition of the spawning biomass may play an important role in the mismatch between SRRs and data. Here we develop a generalization of the Ricker SRR that incorporates age structure by allowing mortality and fecundity rates to depend on maternal age. We provide a flexible SRR with biologically interpretable parameters that can be estimated from existing fisheries time series and use a Bayesian framework that enables parameters to be informed by experimental data. We apply our method to the Icelandic population of Atlantic cod ( Gadus morhua ) and show models that include age structure effects outperform the classical Ricker SRR that ignores age structure. Our results indicate a strong effect of spawning stock age structure on recruitment dynamics in this population. Our approach provides a biologically interpretable and immediately applicable method for investigating the consequences for spawning stock age structure on recruitment.

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