scholarly journals Microgeographical population structure of cod Gadus morhua in the North Sea and west of Scotland: the role of sampling loci and individuals

2009 ◽  
Vol 376 ◽  
pp. 213-225 ◽  
Author(s):  
EE Nielsen ◽  
PJ Wright ◽  
J Hemmer-Hansen ◽  
NA Poulsen ◽  
I Monro Gibb ◽  
...  
Keyword(s):  
Population Structure ◽  
North Sea ◽  
Gadus Morhua ◽  
The North ◽  
The North Sea

An "experiment" on effort allocation of fishing vessels: the role of interference competition and area specialization

2007 ◽  
Vol 64 (2) ◽  
pp. 304-313 ◽  
Author(s):  
Jan-Jaap Poos ◽  
Adriaan D Rijnsdorp
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Seasonal Pattern ◽  
Interference Competition ◽  
Catch Rate ◽  
The North ◽  
Closed Area ◽  
Fishing Vessels ◽  
The North Sea

A temporarily closed area established to protect spawning Atlantic cod (Gadus morhua) in the North Sea allowed us to study the response of the Dutch beam trawl fleet exploiting common sole (Solea solea) and plaice (Pleuronectes platessa). A number of vessels left the North Sea 1 month earlier than the normal seasonal pattern. The vessels that continued fishing in the North Sea were concentrated in the remaining open areas. In the first week after the closure, the catch rate decreased by 14%, coinciding with an increase in crowding of 28%. Area specialisation affected the response of individual vessels because vessels without prior experience in the open areas showed a larger decline in catch rate compared with vessels that previously fished in these open areas and were more likely to stop fishing during the closed period. The decrease in catch rate in response to the increase in competitor density allowed us to estimate the strength of the interference competition.

GENETIC POPULATION STRUCTURE OFPSEUDO-NITZSCHIA PUNGENS(BACILLARIOPHYCEAE) FROM THE PACIFIC NORTHWEST AND THE NORTH SEA

2009 ◽  
Vol 45 (5) ◽  
pp. 1037-1045 ◽  
Author(s):  
Nicolaus G. Adams ◽  
Vera L. Trainer ◽  
Gabrielle Rocap ◽  
Russell P. Herwig ◽  
Lorenz Hauser
Keyword(s):  
Population Structure ◽  
Pacific Northwest ◽  
North Sea ◽  
Genetic Population Structure ◽  
Genetic Population ◽  
The North ◽  
The Pacific ◽  
The North Sea ◽  
Nitzschia Pungens

Population structure of harbour porpoises in the Baltic region: evidence of separation based on geometric morphometric comparisons

2012 ◽  
Vol 92 (8) ◽  
pp. 1669-1676 ◽  
Author(s):  
Anders Galatius ◽  
Carl Christian Kinze ◽  
Jonas Teilmann
Keyword(s):  
Population Structure ◽  
Baltic Sea ◽  
North Sea ◽  
Harbour Porpoise ◽  
Baltic Region ◽  
Geometric Morphometric ◽  
The North ◽  
The North Sea ◽  
The Baltic ◽  
Separate Population

The harbour porpoise is seriously depleted and threatened with extinction in the Baltic Sea. It is usually assumed that Baltic porpoises form a separate population unit, although the evidence for this has been disputed lately. Here, a 3-D geometric morphometric approach was employed to test a number of hypotheses regarding population structure of the harbour porpoise in the Baltic region. 277 porpoise skulls from Denmark, Sweden, Finland, Germany and Poland were measured with a suite of 3-D landmarks. Statistical analyses revealed highly significant shape differences between porpoises from the North Sea, Belt Sea and the inner Baltic Sea. A comparison of the directionalities of the shape vectors between these units found differences that cannot be attributed to a general, continual shape trend going from the North Sea to the inner Baltic Sea. These vectors indicate a morphological adaptation to the specific sub-areas. Such adaptation may be the result of the topographic peculiarities of the area with variable topography and shallow waters, e.g. in the Belt Sea porpoises, there may be a greater reliance on benthic and demersal prey. The present results show that isolation by distance alone is an unlikely explanation for the differences found within the Baltic region and thus support previously reported molecular indications of a separate population within the inner Baltic Sea.

scholarly journals The consumption of zooplankton by early life stages of fish in the North Sea

2007 ◽  
Vol 64 (9) ◽  
pp. 1650-1663 ◽  
Author(s):  
Michael R. Heath
Keyword(s):  
North Sea ◽  
Early Life ◽  
Life Stages ◽  
Early Life Stages ◽  
The North ◽  
The North Sea ◽  
Zooplankton Consumption ◽  
Zooplankton Production ◽  
Fish Early Life Stages

Abstract Heath, M. R. 2007. The consumption of zooplankton by early life stages of fish in the North Sea. – ICES Journal of Marine Science, 64: 1650–1663. Previous work has shown that during the 1970s, fish and carnivorous macrozooplankton together consumed ∼22 gC m−2 year−1 of mesozooplankton, principally copepods. Consumption declined to ∼17 gC m−2 year−1 during the 1990s, mainly because of a reduction in fish production. The zooplankton production required to meet this demand seems to be approximately accounted for by estimates of new primary production, but there are additional sinks for zooplankton production attributable to predation by, for example, gelatinous species. Additionally, the consumption of zooplankton by early life stages of fish is difficult to assess and could be larger than implied by the earlier analysis. Here, the role of fish early life stages in zooplankton consumption is re-assessed, and found to be approximately double that previously estimated. Some 28% of the zooplankton consumption by fish is now estimated to be attributable to early life stages, resulting in an estimate of zooplankton consumption by the fish community as a whole 14% higher. Taken overall, the consumption of zooplankton production by fish and other planktivorous predators is now estimated to be 19–25 gC m−2 year−1.

scholarly journals First record of brown colouration of Atlantic cod (Gadus morhua, L.) from the North Sea

Oceanologia ◽  
2014 ◽  
Vol 56 (1) ◽  
pp. 159-163
Author(s):  
Agnieszka Rybczyk ◽  
Przemysław Czerniejewski ◽  
Joanna Rokicka-Praxmajer
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
First Record ◽  
The North ◽  
The North Sea

Diel variation of stomach contents of North Sea cod (Gadus morhua) during a 24-h fishing survey: an analysis using generalized additive models

2000 ◽  
Vol 57 (12) ◽  
pp. 2363-2367 ◽  
Author(s):  
Sara A Adlerstein ◽  
Henny C Welleman
Keyword(s):  
North Sea ◽  
Stomach Content ◽  
Gadus Morhua ◽  
Generalized Additive Models ◽  
Stomach Contents ◽  
Additive Models ◽  
Large Prey ◽  
Diel Variation ◽  
The North ◽  
The North Sea

Results show that the weight of cod (Gadus morhua) stomach contents sampled in the North Sea varies significantly within 24 h. To determine whether feeding varied with time, over 1100 cod stomachs were collected around the clock between 7 and 18 May 1984 in two areas in the central North Sea thought to be representative for feeding studies. Here we investigate temporal feeding patterns based on the analysis of stomach-content data, using generalized additive models (GAMs). Results show significant variation of content weight and indicate morning and evening peaks. The relative peak importance differed between and within areas. We propose that differences are due to diet composition, namely, prey size and diel availability. Cod fed primarily on molluscs, mainly ocean quahog (Cyprina islandica), crustaceans, sandeels (Ammodytes spp.), haddock (Melanogrammus aeglefinus), herring (Clupea harrengus), and several flatfish species. In one area, the diet was dominated by fish, relatively large prey that perform diel vertical migration, and in the other by invertebrates, smaller prey that are digested faster. The diel pattern was more pronounced where invertebrate prey were dominant. Generalisation of results and implications for predation-mortality estimates based on data from the North Sea Stomach Content Database, used to implement multispecies models in the region, are discussed.

scholarly journals Shifts in spawning phenology of cod linked to rising sea temperatures

2017 ◽  
Vol 74 (6) ◽  
pp. 1561-1573 ◽  
Author(s):  
Kate McQueen ◽  
C. Tara Marshall
Keyword(s):  
Climate Change ◽  
North Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Size Structure ◽  
Gonadal Development ◽  
Trophic Levels ◽  
Irish Sea ◽  
The North ◽  
The North Sea

AbstractWarming temperatures caused by climate change have the potential to impact spawning phenology of temperate marine fish as some species have temperature-dependent gonadal development. Inter-annual variation in the timing of Atlantic cod (Gadus morhua) spawning in the northern North Sea, central North Sea and Irish Sea was estimated by calculating an annual peak roe month (PRM) from records of roe landings spanning the last three decades. A trend towards earlier PRM was found in all three regions, with estimates of shifts in PRM ranging from 0.9 to 2.4 weeks per decade. Temperatures experienced by cod during early vitellogenesis correlated negatively with PRM, suggesting that rising sea temperatures have contributed to a shift in spawning phenology. A concurrent reduction in the mean size of spawning females excluded the possibility that earlier spawning was due to a shift in size structure towards larger individuals, as large cod spawn earlier than smaller-sized individuals in the North Sea. Further research into the effects of climate change on the phenology of different trophic levels within the North Sea ecosystem should be undertaken to determine whether climate change-induced shifts in spawning phenology will result in a temporal mismatch between cod larvae and their planktonic prey.

Sign in / Sign up

Export Citation Format

Share Document