Retention of juveniles within a hybrid zone between North Sea and Baltic Sea Atlantic cod (Gadus morhua)

Elucidating the relative roles of dispersal and retention of juvenile stages is an important issue for understanding population structure and evolution in marine organisms. We investigated the genetic population structure of juvenile Atlantic cod (Gadus morhua) within the transition zone between the North Sea and the Baltic Sea, employing nine microsatellite loci, and compared our data with adult cod data from the same area. Small but statistically significant overall differentiation (Fst = 0.003) was found among juvenile samples. Samples of juveniles grouped genetically with adult samples from the same geographical regions. Individual admixture analysis of a large sample of juveniles taken within the transition zone showed that the patterns of genetic differentiation could not be explained by mixing of pure North Sea and Baltic Sea individuals. Instead, the high number of juveniles with intermediate genotypes was compatible with a scenario of exclusive local (transition zone) origin. The results support the hypothesis that population structure in marine fishes is maintained by the retention of juveniles.

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Epidemiology of pseudobranchial tumours in Atlantic cod(Gadus morhua) from the North Sea and the Baltic Sea

Helgoländer Meeresuntersuchungen ◽

10.1007/bf01999133 ◽

1982 ◽

Vol 35 (4) ◽

pp. 425-437 ◽

Cited By ~ 5

Author(s):

B. Watermann ◽

V. Dethlefsen ◽

M. Hoppenheit

Keyword(s):

Baltic Sea ◽

North Sea ◽

Gadus Morhua ◽

Atlantic Cod ◽

The Baltic Sea ◽

The North ◽

The North Sea ◽

The Baltic

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Histology of pseudobranchial tumours in Atlantic cod(Gadus morhua) from the North Sea and the Baltic Sea

Helgoländer Meeresuntersuchungen ◽

10.1007/bf01997554 ◽

1982 ◽

Vol 35 (2) ◽

pp. 231-242 ◽

Cited By ~ 17

Author(s):

B. Watermann ◽

V. Dethlefsen

Keyword(s):

Baltic Sea ◽

North Sea ◽

Gadus Morhua ◽

Atlantic Cod ◽

The Baltic Sea ◽

The North ◽

The North Sea ◽

The Baltic

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

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315412000513 ◽

2012 ◽

Vol 92 (8) ◽

pp. 1669-1676 ◽

Cited By ~ 23

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.

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Genetic and morphological variation in Echinorhynchus gadi Zoega in Müller, 1776 (Acanthocephala: Echinorhynchidae) from Atlantic cod Gadus morhua L.

Journal of Helminthology ◽

10.1017/s0022149x10000891 ◽

2011 ◽

Vol 86 (1) ◽

pp. 16-25 ◽

Cited By ~ 13

Author(s):

E. Sobecka ◽

B. Szostakowska ◽

K. MacKenzie ◽

W. Hemmingsen ◽

S. Prajsnar ◽

...

Keyword(s):

Baltic Sea ◽

Population Biology ◽

Gadus Morhua ◽

Dna Analysis ◽

Atlantic Cod ◽

Morphological Features ◽

The Baltic Sea ◽

Systematic Classification ◽

The North ◽

The Baltic

AbstractPrevious studies have shown considerable variability in morphological features and the existence of genetically distinct sibling species in the acanthocephalan Echinorhynchus gadi Zoega in Müller, 1776. The aim of the present study was to follow up and extend those earlier studies by using a combination of DNA analysis and morphometrics to investigate differences between samples of E. gadi from Atlantic cod Gadus morhua L. caught at five fishing grounds in the Baltic Sea and three in different parts of the North Atlantic. Twelve morphological features were measured in 431 specimens of E. gadi, 99 individuals were studied by polymerase chain reaction-restriction fragment length polymorphosm (PCR-RFLP), and selected PCR products were sequenced. The molecular analyses showed the nucleotide sequences of E. gadi rDNA from cod caught at all the sampling sites to be identical. The comparative morphological study, in contrast, revealed significant differences between samples of E. gadi from different sampling sites and showed the separation of E. gadi into two groups corresponding approximately to the systematic classification of cod into the two subspecies, Atlantic G. morhua morhua and Baltic G. morhua callarias. The E. gadi infrapopulation size had a significant effect on some of the morphological features. The results are discussed in relation to cod population biology, the hydrography of the study area and the history of the Baltic Sea formation.

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Where do you come from, where do you go: Early life stage drift and migrations of cod inferred from otolith microchemistry and genetic population assignment

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2020-0409 ◽

2021 ◽

Author(s):

Karin Hüssy ◽

Christoffer Moesgaard Albertsen ◽

Jakob Hemmer-Hansen ◽

Morten Vinther ◽

Simon Hansen Serre ◽

...

Keyword(s):

Baltic Sea ◽

North Sea ◽

Early Life ◽

Atlantic Cod ◽

Life Stage ◽

Early Life Stage ◽

Otolith Microchemistry ◽

Genetic Population ◽

The North ◽

The North Sea

This study investigates stock mixing of genetically distinct Atlantic cod (Gadus morhua) stocks in the Kattegat, an area geographically located between the North Sea and the Baltic Sea, by combining genetic population identification with habitat assignments from hatch to capture from otolith microchemistry. Cod captured in Kattegat were genetically assigned to either the North Sea or the endemic Kattegat population. Otolith chemical fingerprints differed significantly between populations during the larval and pelagic juvenile stage with higher strontium and lower barium and manganese concentrations in the North Sea population than the Kattegat population, indicating that North Sea cod are spawned in the North Sea or Skagerrak and drift into the Kattegat during the early life stages. Individual cod of both populations undertook frequent migrations to other areas, with < 25 % of individuals remaining resident within the Kattegat throughout their life. Across seasons and age classes, the two populations were most frequently distributed in the Kattegat (67 %), with approximately 25 % distributed in the western Baltic Sea and < 10 % in the Skagerrak/North Sea.

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f06-177 ◽

2007 ◽

Vol 64 (2) ◽

pp. 304-313 ◽

Cited By ~ 56

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.

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Model calculations of the effects of present and future emissions of air pollutants from shipping in the Baltic Sea and the North Sea

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-21943-2014 ◽

2014 ◽

Vol 14 (15) ◽

pp. 21943-21974 ◽

Cited By ~ 4

Author(s):

J. E. Jonson ◽

J. P. Jalkanen ◽

L. Johansson ◽

M. Gauss ◽

H. A. C. Denier van der Gon

Keyword(s):

Baltic Sea ◽

North Sea ◽

Years Of Life Lost ◽

Ship Emissions ◽

The Baltic Sea ◽

Model Calculations ◽

The North ◽

Before And After ◽

The North Sea ◽

The Baltic

Abstract. Land-based emissions of air pollutants in Europe have steadily decreased over the past two decades, and this decrease is expected to continue. Within the same time span emissions from shipping have increased, although recently sulphur emissions, and subsequently particle emissions, have decreased in EU ports and in the Baltic Sea and the North Sea, defined as SECAs (Sulphur Emission Control Areas). The maximum allowed sulphur content in marine fuels in EU ports is now 0.1%, as required by the European Union sulphur directive. In the SECAs the maximum fuel content of sulphur is currently 1% (the global average is about 2.4%). This will be reduced to 0.1% from 2015, following the new IMO rules (International Maritime Organisation). In order to assess the effects of ship emissions in and around the Baltic Sea and the North Sea, regional model calculations with the EMEP air pollution model have been made on a 1/4° longitude × 1/8° latitude resolution, using ship emissions in the Baltic Sea and the North Sea that are based on accurate ship positioning data. The effects on depositions and air pollution and the resulting number of years of life lost (YOLL) have been calculated by comparing model calculations with and without ship emissions in the two sea areas. The calculations have been made with emissions representative of 2009 and 2011, i.e. before and after the implementation of stricter controls on sulphur emissions from mid 2010. The calculations with present emissions show that per person, an additional 0.1–0.2 years of life lost is estimated in areas close to the major ship tracks with present emission levels. Comparisons of model calculations with emissions before and after the implementation of stricter emission control on sulphur show a general decrease in calculated particle concentration. At the same time, however, an increase in ship activity has resulted in higher emissions and subsequently air concentrations, in particular of NOx, especially in and around several major ports. Additional model calculations have been made with land based and ship emissions representative of year 2030. Following a decrease in emissions, air quality is expected to improve, and depositions to be reduced. Particles from shipping are expected to decrease as a result of emission controls in the SECAs. Further controls of NOx emissions from shipping are not decided, and calculations are presented with and without such controls.

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