Feeding and growth of Atlantic cod (Gadus morhua L.) in the eastern Baltic Sea under environmental change

2019 ◽  
Vol 77 (2) ◽  
pp. 624-632 ◽  
Author(s):  
Stefan Neuenfeldt ◽  
Valerio Bartolino ◽  
Alessandro Orio ◽  
Ken H Andersen ◽  
Niels G Andersen ◽  
...  
Keyword(s):  
Growth Rate ◽  
Baltic Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Somatic Growth ◽  
Environmental Forcing ◽  
Average Growth ◽  
Scarce Resources ◽  
Size At Age ◽  
Eastern Baltic

Abstract Five decades of stomach content data allowed insight into the development of consumption, diet composition, and resulting somatic growth of Gadus morhua (Atlantic cod) in the eastern Baltic Sea. We show a recent reversal in feeding level over body length. Present feeding levels of small cod indicate severe growth limitation and increased starvation-related mortality. For young cod, the low growth rate and the high mortality rate are manifested through a reduction in size-at-age. The low feeding levels are likely the result of a decrease in benthic prey abundance due to increased hypoxic areas, while decreasing abundances of pelagic species in the area of cod distribution have prevented a compensatory shift in diet. Our study emphasizes that environmental forcing and the decline in pelagic prey caused changes in consumption and growth rates of small cod. The food reduction is amplified by stunted growth leading to high densities of cod of smaller size competing for the scarce resources. The average growth rate is negative, and only individuals with feeding levels well above average will survive, though growing slowly. These results suggest that the relation between consumption rate, somatic growth and predatorprey population densities is strongly environmentally mediated.

Reconstructing historical stock development of Atlantic cod (Gadus morhua) in the eastern Baltic Sea before the beginning of intensive exploitation

2008 ◽  
Vol 65 (12) ◽  
pp. 2728-2741 ◽  
Author(s):  
Margit Eero ◽  
Friedrich W. Köster ◽  
Brian R. MacKenzie
Keyword(s):  
Baltic Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Reference Level ◽  
Stock Size ◽  
Intensive Exploitation ◽  
Spawning Stock ◽  
The 1950S ◽  
The Baltic ◽  
Eastern Baltic

The landings of Atlantic cod ( Gadus morhua ) in the eastern Baltic Sea in the early decades of the 20th century were below 50 thousand tonnes and therefore lower than in recent years at very low stock size. These low landings have largely contributed to a perception that the stock size was also low before the 1950s. In this investigation, we demonstrate that cod spawning stock biomass in the years 1925–1944 fluctuated in a similar range as in the periods from the 1950s to the mid-1970s and from the late 1980s onwards and was in most of these years at least twice as high as at present. Fishing mortality before the 1940s was below 0.2, but reached moderate levels during the Second World War. The stock size before the war may be considered as a reference level of biomass at low fishing impact, providing important information for the management of fisheries and the Baltic ecosystem.

scholarly journals Feeding and growth of Atlantic cod (Gadus morhua L.) in the eastern Baltic Sea under environmental change

2020 ◽  
Vol 77 (2) ◽  
pp. 858-858
Author(s):  
Stefan Neuenfeldt ◽  
Valerio Bartolino ◽  
Alessandro Orio ◽  
Ken H Andersen ◽  
Niels G Andersen ◽  
...  
Keyword(s):  
Environmental Change ◽  
Baltic Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Eastern Baltic

Relationships Between RNA–DNA Ratio, Prey Density, and Growth Rate in Atlantic Cod (Gadus morhua) Larvae

1979 ◽  
Vol 36 (12) ◽  
pp. 1497-1502 ◽  
Author(s):  
L. J. Buckley
Keyword(s):  
Growth Rate ◽  
Nutritional Status ◽  
Growth Rates ◽  
Prey Density ◽  
Gadus Morhua ◽  
Slow Growth ◽  
Atlantic Cod ◽  
Larval Fish ◽  
Dry Weight ◽  
Dna And Rna

The protein, DNA, and RNA content of larvae maintained at 1.0 plankter/mL increased at the rates of 9.3, 9.9, and 9.8% per day, respectively, for the 5 wk after hatching. Protein reserves of larvae held at 0 or 0.2 plankters/mL were depleted by 45 and 35%, respectively, prior to death 12–13 d after hatching. Starved larvae had similar protein concentrations (percent of dry weight), lower RNA concentrations, and higher DNA concentrations than fed larvae. Larvae held at higher plankton densities had higher RNA–DNA ratios and faster growth rates than larvae held at lower plankton densities. The RNA–DNA ratio was significantly correlated (P < 0.01) with the protein growth rate. The RNA–DNA ratio appears to be a useful index of nutritional status in larval Atlantic cod (Gadus morhua) and may be useful for determining if cod larvae were in a period of rapid or slow growth at the time of capture. Key words: RNA–DNA ratio, starvation, protein, nucleic acids, growth, larval fish, Atlantic cod

Otolith growth and zone formation during first maturity and spawning of Atlantic cod (Gadus morhua)

2020 ◽  
Vol 77 (1) ◽  
pp. 113-123 ◽  
Author(s):  
Christian Irgens ◽  
Arild Folkvord ◽  
Håkon Otterå ◽  
Olav S. Kjesbu
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Somatic Growth ◽  
Otolith Growth ◽  
Zone Formation ◽  
Stock Biomass ◽  
Tank Experiment ◽  
The Individual ◽  
First Maturity

Specific impacts of somatic growth, sexual maturation, and spawning events on otolith zone formation in Atlantic cod (Gadus morhua) were assessed in a 33-month tank experiment, using Barents Sea cod and Norwegian coastal cod. High and low feeding ration combinations were used to mimic environmental stressors in the field. For both stocks, apparent macrostructural “spawning zones” in otoliths are registered in statutory stock monitoring programs to estimate age at maturity, thus adding key information to stock biomass assessments. We found that substantial energy investments in reproduction caused reductions in otolith growth and altered proportional width between translucent and opaque zones. These effects, however, were only statistically significant among individuals with high reproductive investments, while otoliths from individuals with low investments did not differ from the otoliths for immatures. Reproduction may thus not necessarily induce spawning zones, and alternatively, spawning zones may not necessarily reflect reproduction. Altogether, this suggests that the individual energy level, as a premise for metabolic activity, plays a key role in the formation of such zones and thus is related to environmental conditions.

Thermoregulatory behaviour in cod: Is the thermal preference in free-ranging adult Atlantic cod affected by food abundance?

2019 ◽  
Vol 76 (9) ◽  
pp. 1515-1527 ◽  
Author(s):  
Björn Björnsson
Keyword(s):  
Growth Rate ◽  
Data Storage ◽  
Gadus Morhua ◽  
Cold Water ◽  
Atlantic Cod ◽  
Vertical Mixing ◽  
Metabolic Energy ◽  
Fat Reserves ◽  
Free Ranging ◽  
Thermoregulatory Behaviour

This study supports the hypothesis that well-fed cod (Gadus morhua) seek higher temperatures to increase growth rate, and poorly fed cod select lower temperatures to save metabolic energy. Depth and temperature of free-ranging adult cod (44–79 cm) were studied with data storage tags as part of a ranching project in an Icelandic fjord. Forage fish were regularly provided at four feeding stations where cod formed distinct “herds” (herd cod) that did not mingle much with the rest of the unconditioned cod in the fjord (wild cod). Several parameters (stomach fullness, liver index (fat reserves), condition factor, and growth rate) indicated that food intake was much greater in herd cod than in wild cod. In August, when the thermocline was well established, the herd cod remained in shallow (15–35 m) and warm water (8–10 °C), whereas the wild cod stayed in deep (80–90 m) and cold water (3–4 °C), but occasionally both groups explored depths and temperatures outside their preferred range. After vertical mixing in autumn when thermoregulation was not possible, the depth difference between the two groups decreased significantly.

scholarly journals DNA HETEROZYGOSITY AND GROWTH RATE IN THE ATLANTIC COD GADUS MORHUA (L)

Evolution ◽  
1998 ◽  
Vol 52 (3) ◽  
pp. 915-920 ◽  
Author(s):  
Grant H. Pogson ◽  
Svein Erik Fevolden
Keyword(s):  
Growth Rate ◽  
Gadus Morhua ◽  
Atlantic Cod

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.

Comparative Survival and Growth of Two Strains of Atlantic Cod (Gadus morhua) through the Early Life Stages in a Marine Pond

1994 ◽  
Vol 51 (5) ◽  
pp. 1012-1023 ◽  
Author(s):  
Geir Blom ◽  
Terje Svåsand ◽  
Knut E. Jørstad ◽  
Håkon Otterå ◽  
Ole I. Paulsen ◽  
...  
Keyword(s):  
Body Size ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Larval Mortality ◽  
Food Limitation ◽  
Juvenile Stage ◽  
Average Growth ◽  
Juvenile Mortality ◽  
Early Juvenile Stage ◽  
Survival And Growth

Survival and growth of two strains of Atlantic cod (Gadus morhua) were compared through the larval and juvenile stages in a marine pond in western Norway in 1990 and 1991. Strain A was homozygous for the genetic marker allele GPI-1*30 at the glucose phosphate isomerase (GPI) locus expressed in white muscle, and Strain B possessed other GPI-1* genotypes, in 1990 the frequency of Strain B increased significantly from the larval to the juvenile stage; however, in 1991 the frequency of Strain A increased slightly but not significantly from the larval to the juvenile phase. Larval mortality did not differ significantly between strains any year, but juvenile mortality was significantly lower in Strain B in 1990 and Strain A in 1991. Average growth rates in length estimated from regressions were not significantly different between strains during the larval and juvenile period any year, but initial length was significantly larger in Strain B in 1990 and Strain A in 1991. Our results indicated that food limitation during the early juvenile stage induced differential size-selective mortality among the strains due to small differences in body size and actual age between strains. Body size did not become important for survival until the food-limited regime had occurred.

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