scholarly journals Effect of a fish stock's demographic structure on offspring survival and sensitivity to climate

2017 ◽  
Vol 114 (6) ◽  
pp. 1347-1352 ◽  
Author(s):  
Leif Christian Stige ◽  
Natalia A. Yaragina ◽  
Øystein Langangen ◽  
Bjarte Bogstad ◽  
Nils Chr. Stenseth ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Condition Index ◽  
Wide Distribution ◽  
Commercial Fishing ◽  
Demographic Structure ◽  
Data Set ◽  
Spawning Period ◽  
Spawning Stock ◽  
Eggs And Larvae

Commercial fishing generally removes large and old individuals from fish stocks, reducing mean age and age diversity among spawners. It is feared that these demographic changes lead to lower and more variable recruitment to the stocks. A key proposed pathway is that juvenation and reduced size distribution causes reduced ranges in spawning period, spawning location, and egg buoyancy; this is proposed to lead to reduced spatial distribution of fish eggs and larvae, more homogeneous ambient environmental conditions within each year-class, and reduced buffering against negative environmental influences. However, few, if any, studies have confirmed a causal link from spawning stock demographic structure through egg and larval distribution to year class strength at recruitment. We here show that high mean age and size in the spawning stock of Barents Sea cod (Gadus morhua) is positively associated with high abundance and wide spatiotemporal distribution of cod eggs. We find, however, no support for the hypothesis that a wide egg distribution leads to higher recruitment or a weaker recruitment–temperature correlation. These results are based on statistical analyses of a spatially resolved data set on cod eggs covering a period (1959−1993) with large changes in biomass and demographic structure of spawners. The analyses also account for significant effects of spawning stock biomass and a liver condition index on egg abundance and distribution. Our results suggest that the buffering effect of a geographically wide distribution of eggs and larvae on fish recruitment may be insignificant compared with other impacts.

scholarly journals Evaluation of the current state of small pelagic fisheries in the Colombian Pacific: ensuring the sustainability of the resource and evaluating its response to climatic events

2013 ◽  
Vol 33 ◽  
pp. 63-68 ◽  
Author(s):  
L. A. Zapata ◽  
B. S. Beltrán-León ◽  
J. C. Herrera ◽  
P. Jiménez-Tello ◽  
L. M. Prieto ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Commercial Fishing ◽  
Spawning Period ◽  
Thermal Anomalies ◽  
Current State ◽  
Management Measures ◽  
Canned Foods ◽  
Total Capture ◽  
Reproductive Processes ◽  
Eggs And Larvae

Abstract. Commercial fishing of small pelagic species in Colombia, mainly "carduma" (Cetengraulis mysticetus) and "plumuda" (Opisthonema spp.), has been recorded since 1970. Both are used to produce fish meal for aquaculture and poultry and for canned foods. These two species are filter feeders, and therefore support higher levels of the food chain (other fish, birds and marine mammals), and artisanal fishermen use them as bait. Between 2005 and 2010, 86.131 t have been captured (X = 14.355 t yr−1), and a strong reduction was noticed in 2009 (6.969 t). Carduma is considered a total spawning species. However, from 1997 to 2000 and from 2008 to date, atypical reproductive behavior of the species has been observed, including partition of the spawning period and the reduction of the volume of eggs and larvae released to the environment. Both situations are linked to thermal anomalies such as El Niño and La Niña events. Therefore, the process of assigning the global quota of extraction has been revised to take into account the reduction of total capture during the last years and the inconsistencies of the reproductive processes. The Ministry of Agriculture reduced the quota by 10%, leaving available a total of 27 000 t for 2010 and reduced it again to 25 000 t for 2011. It is important to maintain the management measures that are already implemented on this resource (bans during reproduction seasons, catch quotas, regulation of mesh sizes for the fishing nets, and limiting the number of new vessels) and considering other measures such as season closure for recruitment and establishment of marine protected areas to further contribute to the sustainability of these fisheries.

scholarly journals Effects of climate and spawning stock structure on the spatial distribution of Northeast Arctic cod larvae

2020 ◽  
Author(s):  
Clarissa Akemi Kajiya Endo ◽  
Frode B Vikebø ◽  
Natalia A Yaragina ◽  
Solfrid Sætre Hjøllo ◽  
Leif Christian Stige
Keyword(s):  
Spatial Distribution ◽  
Environmental Variables ◽  
Barents Sea ◽  
Condition Index ◽  
Ocean Current ◽  
Larval Abundance ◽  
Near Surface ◽  
Spawning Stock ◽  
Long Time ◽  
Abundance And Distribution

Abstract The spatial distribution of fish early life stages can impact recruitment at later stages and affect population size and resilience. Northeast Arctic (NEA) cod spawning occurs along the Norwegian coast. Eggs, larvae, and pelagic juveniles drift near-surface towards the Barents Sea nursery area. In this study, a 35-year long time series of NEA cod larvae data was analysed in combination with factors that potentially may affect the distribution of eggs and larvae. These factors included biological aspects of the spawning stock, and environmental variables, such as water temperature, wind, ocean current, and prey abundance. Our aim was to shed light on how these factors influence larval abundance and distribution and how larval abundance and distribution influenced recruitment at age 3. We found that biomass and mean weight of the spawners were positively associated with larval abundance and that a high liver condition index of the spawners was associated with a north-easterly distribution of the larvae. The environmental variables showed generally weak or no correlations with abundance or distribution of larvae. Lastly, we found significant association between larval abundance and year-class abundance at age 3, while the spatial distribution metrics of the larvae, i.e. distribution extent, mean longitude, and mean latitude, showed no significant association with future year-class abundance.

scholarly journals Feeding of mature cod (Gadus morhua) on the spawning grounds in Lofoten

2008 ◽  
Vol 65 (4) ◽  
pp. 571-580 ◽  
Author(s):  
Kathrine Michalsen ◽  
Edda Johannesen ◽  
Bjarte Bogstad
Keyword(s):  
Diet Composition ◽  
Gadus Morhua ◽  
Barents Sea ◽  
Lower Proportion ◽  
Clupea Harengus ◽  
Stomach Fullness ◽  
Spawning Grounds ◽  
Spawning Period ◽  
Established Fact ◽  
A Minor

Abstract Michalsen, K., Johannesen, E., and Bogstad, B. 2008. Feeding of mature cod (Gadus morhua) on the spawning grounds in Lofoten. – ICES Journal of Marine Science, 65: 571–580. Many authors state that cod (Gadus morhua) do not feed during the spawning period. However, this more or less established fact has rarely been investigated in the field. Here, the content of stomachs from Northeast Arctic cod (NEAC) and Norwegian coastal cod (NCC) sampled from the spawning ground in Lofoten were examined over a 10-year period (1996–2006). The occurrence of food in the stomachs of spawning cod, stomach fullness, diet composition, and variation in these variables between NEAC and NCC, year, and sex were analysed and compared. The analysis shows that cod do feed, even when they are in a spawning state. NCC had a lower proportion of empty stomachs and the stomachs were fuller than those from NEAC. Females had a lower proportion of empty stomachs than males and their stomachs were in general fuller. Herring (Clupea harengus) dominated the diet of cod. However, cod consumption of herring on the spawning grounds seems to be a minor source of mortality on herring. Although spawning cod do feed, the proportion of empty stomachs was higher and stomach fullness was lower than in stomachs of NEAC from the Barents Sea.

Population Dynamics of the Arcto-Norwegian Cod

1967 ◽  
Vol 24 (1) ◽  
pp. 145-190 ◽  
Author(s):  
D. J. Garrod
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Fishing Effort ◽  
Catch Per Unit Effort ◽  
Group Iii ◽  
Spawning Stock ◽  
Stock Recruitment ◽  
Post War ◽  
The One ◽  
Definition Of

By reason of its geographical distribution, the Arcto-Norwegian cod (Gadus morhua) supports three distinct fisheries, two feeding fisheries in the Barents Sea and at Bear Island–Spitsbergen, and a spawning fishery off the Norway coast. In the past this diversity of fishing on the one stock has made it difficult to unify all the data to give an overall description of post-war changes in the stock. In this contribution three modifications of conventional procedures are introduced which enable this to be done. These are: (i) a system of weighting the catch per unit effort data from each fishery to a level of comparability; (ii) a more rigorous definition of the effective fishing effort on each age-group; (iii) a method of estimation of the effective fishing effort on partially recruited age-groups.Using these methods the analysis presents the effects of fishing on each fishery in the context of its effect on the total stock, and at the same time it indicates ways in which factors other than fishing may have influenced the apparent abundance of the stock. The treatment of the data is also used to derive estimates of spawning stock and recruitment of 3-year-old cod for subsequent analysis of stock–recruitment relationships.

scholarly journals Deriving condition indices from standard fisheries databases and evaluating their sensitivity to variation in stored energy reserves

2004 ◽  
Vol 61 (10) ◽  
pp. 1900-1917 ◽  
Author(s):  
C Tara Marshall ◽  
Coby L Needle ◽  
Nathalia A Yaragina ◽  
Adnan M Ajiad ◽  
Evgeny Gusev
Keyword(s):  
Body Size ◽  
Gadus Morhua ◽  
Barents Sea ◽  
Condition Index ◽  
Energy Reserves ◽  
Stored Energy ◽  
Stock Level ◽  
Length Relationship ◽  
Condition Indices

To evaluate interstock differences in condition, it would be advantageous to develop stock-level condition indices from standardized databases on weight and length. This study describes a method for estimating stock-level condition when individual-level observations on length and weight are not easily accessible. For each year in a 56-year time series (1946–2001) for Northeast Arctic cod (Gadus morhua), pseudo-observations of weight and length were generated by pairing the Norwegian and Russian values for weight-at-age provided annually to the assessment working group with estimates of length-at-age derived from the same databases. A weight–length relationship fit to each year was then used to predict weight-at-length, i.e., girth, for a range of standard lengths (30–120 cm). This index was uncorrelated with both the liver condition index and the abundance of Barents Sea capelin (Mallotus villosus), suggesting that at the stock level, the girth of cod is not necessarily indicative of the magnitude of stored energy reserves. Partitioning body size into length-at-age and girth revealed long-term trends in body size. In particular, large/old cod showed substantially higher values of both length-at-age and girth that could be the result of long-term increases in fishing mortality.

scholarly journals Histological analysis invalidates macroscopically determined maturity ogives of the Kattegat cod (Gadus morhua) and suggests new proxies for estimating maturity status of individual fish

2006 ◽  
Vol 63 (3) ◽  
pp. 485-492 ◽  
Author(s):  
F. Vitale ◽  
H. Svedäng ◽  
M. Cardinale
Keyword(s):  
Gadus Morhua ◽  
Histological Analysis ◽  
Spawning Season ◽  
Age Classes ◽  
Data Set ◽  
Histological Techniques ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Correct Estimation ◽  
Spawning Biomass

Abstract Assessment and management of fish populations currently rely on correct estimation of the spawning-stock biomass (SSB), which is based on accurate maturity ogives of the population. Although maturity ogives are usually calculated through macroscopic evaluation of the gonads, histology is generally considered to be more accurate. Here we show that the macroscopic analysis consistently overestimates the proportion of mature females for all age classes in Kattegat cod. The resulting bias showed minimum values for all age classes about a month before the spawning season. Consequently, estimation of the incidence of maturation in females several months before or after the spawning season can only be accurate using histological techniques. Further, the observed bias was used to reconstruct a historical data set of maturity ogives of Kattegat cod. The results showed that female spawning biomass (FSB) might have been overestimated by up to 35%. However, as histological analysis is considered a laborious procedure, proxies of maturity status were sought. It was indicated that the gonadosomatic and hepatosomatic indices may serve as robust proxies for discriminating mature females from immature, thus greatly enhancing the accuracy of the macroscopic maturity evaluation of cod gonads when histological analysis is lacking.

scholarly journals Direct and indirect effects of minke whale abundance on cod and herring fisheries: A scenario experiment for the Greater Barents Sea

2000 ◽  
Vol 2 ◽  
pp. 120 ◽  
Author(s):  
Tore Schweder ◽  
Gro S Hagen ◽  
Einar Hatlebakk
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Minke Whale ◽  
Clupea Harengus ◽  
Prey Abundance ◽  
Balaenoptera Acutorostrata ◽  
Time Step ◽  
Minke Whales ◽  
Spawning Stock ◽  
Capelin Mallotus Villosus

To study the pattern of interaction between minke whale (Balaenoptera acutorostrata) abundance and the main fisheries in the Greater Barents Sea, a simulation experiment was carried out. The population model involves 4 species interconnected in a food web: cod (Gadus morhua), capelin (Mallotus villosus), herring (Clupea harengus) and minke whales. Minke whales are preying on cod, capelin andherring; cod are preying on (young) cod, capelin and herring; herring in the Barents Sea are preying on capelin; while capelin is a bottom prey in the model. The consumption function for minke whales is non-linear in available prey abundance, and is estimated from stomach content data and prey abundance data. The model is dynamic, with a time step of one month, and there are two areas: the BarentsSea and the Norwegian Sea. Minke whale abundances are kept on fixed levels, while recruitment in fish is stochastic.Cod and herring fisheries are managed by quotas targeting fixed fishing mortalities, while capelin is managed with a view to allow the cod to have enough food and leaving a sufficient spawning stock of capelin. The model is simulated over a period of 100 years for a number of fixed levels of minke whaleabundance, and simulated catches of cod, herring and capelin are recorded.The experiment showed interactions between whale abundance and fish catches to be mainly linear. For cod catches, both the direct effect of whales consuming cod, and the indirect effect due to whales competing with cod for food and otherwise altering the ecosystem, are linear and of equal importance. The net effect on the herring fishery is of the same magnitude as the net effect on the cod fishery, witheach extra whale reducing the catches of both species by some 5 tonnes. These conclusions are conditional on the model and its parameterisation.

scholarly journals Escape rate for cod (Gadus morhua) from the codend during buffer towing

2017 ◽  
Vol 75 (2) ◽  
pp. 805-813 ◽  
Author(s):  
Jesse Brinkhof ◽  
Bent Herrmann ◽  
Roger B Larsen ◽  
Manu Sistiaga
Keyword(s):  
Gadus Morhua ◽  
Disease Susceptibility ◽  
Barents Sea ◽  
Escape Rate ◽  
Commercial Fishing ◽  
Size Selectivity ◽  
Size Selection ◽  
Selection For ◽  
Significant Size ◽  
Growth And Reproduction

Abstract The high abundances of Northeast Arctic cod (Gadus morhua) in the Barents Sea have led to the development of a new fishing tactic called buffer towing. On factory trawlers, the trawl is deployed immediately after taking the catch onboard, a tactic used to ensure a continuous supply of fish is being processed. If the desired amount of fish is caught before the catch from the previous haul has been fully processed, the trawl is lifted off the seabed and towed at a given depth at low speed. This is called buffer towing. Cod that escape from the codend when the trawl is shallower than the initial fishing depth are exposed to an increased likelihood of barotrauma-related injuries, increased disease susceptibility, and predation, which could be lethal, or affect growth and reproduction capability. Therefore, this study quantified the escape rate and size selectivity during buffer towing of cod. A new analytical method was applied that allows using the same trawl configuration as applied during commercial fishing and avoids potential bias in the assessment of buffer towing size selection. Our results demonstrated a significant size selection for cod during buffer towing where cod measuring up to at least 42 cm in length were proven to escape. In particular, at least 60% of cod measuring 20 cm were estimated to escape during buffer towing. For cod measuring 30 and 40 cm, at least 53 and 45% were estimated to escape during buffer towing, respectively.

scholarly journals A review of early life history dynamics of Barents Sea cod (Gadus morhua)

2014 ◽  
Vol 71 (8) ◽  
pp. 2064-2087 ◽  
Author(s):  
Geir Ottersen ◽  
Bjarte Bogstad ◽  
Natalia A. Yaragina ◽  
Leif Christian Stige ◽  
Frode B. Vikebø ◽  
...  
Keyword(s):  
Early Life ◽  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Prey Availability ◽  
Life Stage ◽  
Early Life History ◽  
Sea Temperature ◽  
Spawning Stock ◽  
Long Time

Abstract The Barents Sea stock of Atlantic cod (Gadus morhua) is currently the world's largest cod stock. It is also a stock for which long time-series are available and much research has been carried out. With this review, we wish to present an overview and evaluation of the knowledge on Barents Sea cod early life dynamics. The focus is on the effects of the biotic and abiotic drivers, which jointly determine the strength of a year class. A stage-by-stage approach is employed. We summarize and assess the significance of the different processes described in the literature to be at play during each specific life stage, from spawning stock, through eggs, larvae, and pelagic juvenile, to demersal juvenile and recruitment at age 3. Also Russian work is included, some of which until now has not been available to non-Russian readers. Physical drivers examined include sea temperature, advection and dispersal, wind-induced turbulence, and light. Biotic mechanisms studied range from maternal effects and skipped spawning in the adult stock through egg quantity and quality, to prey availability for the larvae and effects of cannibalism on the juveniles. Finally, we evaluate the main hypotheses put forth by Johan Hjort a hundred years ago in the light of our synthesis of present knowledge. A main conclusion is that it is unlikely that there is any one single life stage during which recruitment with any generality is determined.

Sign in / Sign up

Export Citation Format

Share Document