Jarle Mork | Norwegian University of Science and Technology (original) (raw)

Papers by Jarle Mork

Detailed technical procedures for utilizing fish eggs and larvae for species ID as well as enzyme... more Detailed technical procedures for utilizing fish eggs and larvae for species ID as well as enzyme loci genotyping using high-resolution Isoelectric focusinf in polyacrylamide gels are described. Specific applications in marine and anadromous fish species are reported.

Blue whiting from the eastern parts of the Barents Sea are genetically different from other parts... more Blue whiting from the eastern parts of the Barents Sea are genetically different from other parts of the northeast East Atlantic, indicating the existence of a self-sustaining and reproductively isolated or semi-isolated stock there. In mid- and western Barents Sea, its geographic distribution may overlap with Hebrido-Norwegian blue whiting on summer feeding migration. Circumstantial evidence from egg- and larvae distributions supports such a stock structure. Based on observation of unusually large amounts of young blue whiting in the northwest Barents Sea in 2000 and 2001, a sampling scheme encompassing the entire Barents Sea was designed and carried out in winter 2002 to explore the stock origin of these. The polymorphic isozyme loci PGM-1* and IDHP-2*, which showed discriminatory power in earlier blue whiting studies, were employed. The genetic analyses did not reveal overall genetic heterogeneity among geographic samples, but more detailed analysis revealed a statistical signifi...

A total of 521 cod in samples from eight coastal and fjord locations along the Norwegian coast, f... more A total of 521 cod in samples from eight coastal and fjord locations along the Norwegian coast, from the Russian border to mid-Norway, were assessed for allele frequencies at six polymorphic tissue enzyme loci (LDH-3*, PGM-I*, MDH-3*, IDHP-1*, PGI-1* and PGI-2*). According to individual otolith deposition patterns, the four northernmost samples contained both North-East Arctic ("arctic") cod and Norwegian coastal ("coastal") cod. At five of the loci, cod appeared to be one genetically homogeneous unit throughout the sampling area. Locus LDH-3*, however, showed substantial inter-sample genetic heterogeneity. At this locus, samples from northern Norway (north of the Lofoten Islands) had significantly lower frequencies of the LDH-3* 100 allele than those from mid-Norway, whereas the frequencies within each of these groups were not significantly heterogeneous. Among cod typed as "arctic", however, there was a statistically significant surplus of LDH-3* hete...

Marine Ecology Progress Series, 1983

Capelin Mallotus villosus from the large oceanic Barents Sea stock and from a local northern Norw... more Capelin Mallotus villosus from the large oceanic Barents Sea stock and from a local northern Norwegian fjord stock were sampled during 1981 and 1982. Tissue extracts from white skeletal muscle, heart, and liver were analyzed by isoelectric focusing and histochemical enzyme detection. Staining for 11 enzymes revealed at least 20 loci, of which 18 are considered suitable for routine population genetic studies. Tissue distributions, banding patterns, and p1 values of the isozymes are described. The frequency of polymorphic loci (P,,,) was 0.22 f 0.10 and the average heterozygoslty per locus (H3 was 0.008 f 0.007. Inter-sample differences in allele frequencies at 4 polymorphic loci were not significant and thus did not indicate genetic isolation between the fjord stock and the oceanic stock.

Sarsia: North Atlantic Marine Science, 2004

ABSTRACT In order to find polymorphic tissue enzymes and suitable buffer systems for use in popul... more ABSTRACT In order to find polymorphic tissue enzymes and suitable buffer systems for use in population genetic studies of Norway pout ( Trisopterus esmarkii ), a pilot study was performed using 30 individual specimens from one location. A set of potentially useful genetic markers was established, based on electrophoretic analysis of 22 different tissue enzymes in three different buffer systems. The initial analyses revealed 31 putative loci, from which eight were considered to be reliable in routine scoring. Here, a total of 1797 specimens of Norway pout, from 23 individual locations in the fjords and coastal waters of Norway, were scored for these eight loci. Variant alleles were found at all loci. At least five of the loci were polymorphic by the 0.99 criterion ( LDH-2 *, GPI-1 *, GPI-2 *, G3PDH-2 *, IDHP-2 *) and one locus also by the 0.95 criterion ( LDH-2 *). The frequency of polymorphic loci were P 0.99 ≥ 0.625 and P 0.95 = 0.125. The average heterozygosity over all loci based on Hardy-Weinberg expectations was H = 0.072 (±0.050). Here the details of electrophoretic conditions, staining procedures and tissue manifestation of the loci and the allele designations are described.

ICES Journal of Marine Science, 2005

ABSTRACT The blue whiting, Micromesistius poutassou (Teleostei, Gadidae) is found between latitud... more ABSTRACT The blue whiting, Micromesistius poutassou (Teleostei, Gadidae) is found between latitudes 26 degrees and 82 degrees N along the continental margin of the Northeast Atlantic, with smaller Populations in the Northwest Atlantic and the Mediterranean. There is an annual spawning aggregation on the Porcupine Bank and Hebridean Shelf (west of Ireland and Scotland, respectively), where most of the blue whiting population of the Northeast Atlantic spawns. Analysis of samples from the Barents Sea, the Northeast Atlantic, and the Mediterranean (n = 850, 11 samples) using one minisatellite and five microsatellite loci revealed significant geographic heterogeneity and isolated populations at the extremes of the species range in the Barents Sea and the Mediterranean. Furthermore, there was evidence of genetic heterogeneity among samples taken during the spawning season on the Porcupine Bank and Hebridean Shelf, with highly significant differentiation between the samples taken in the Hebrides in 1992 and 1998. (c) 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.

Marine and Coastal Fisheries, 2015

ABSTRACT Worldwide increases of jellyfish has occurred during the last several decades. A dense p... more ABSTRACT Worldwide increases of jellyfish has occurred during the last several decades. A dense population of a large scyphozoan jellyfish, Periphylla periphylla, has established itself as top predator in the Trondheimsfjord in Norway, impacting traditional fisheries. On this background we discuss the adaptive capacity of artisanal fishers and stakeholder involvement in environmental management. A serendipitous discovery was that fishers report that their capacity to adapt to the presence of jellyfish in fact was sufficient. What they could not adapt to, within the context of jellyfish proliferation, was top-down decisions from the national government allowing purse seiners into the fjord to harvest Sprat Sprattus sprattus and Atlantic Herring Clupea harengus rest quotas and thereby also large bycatches of the local codfishes. This harvest was perceived more detrimental to their fishery than was the jellyfish invasion. Relative to fisheries management's choice of regulatory mechanisms during times of climatic change, we argue that by involving stakeholders intimately, the resulting policy advice will be experienced bottom-up and, thus, more legitimate and serendipitous results of a critical nature are more likely to surface.

Journal of Fish Biology

Genetic analysis of the four Trisopterus (Gadidae) taxa suggests that the interrelationships of t... more Genetic analysis of the four Trisopterus (Gadidae) taxa suggests that the interrelationships of the two morphs of poor cod (T. minutus minutus in the Atlantic and T. minutus capelanus in the Mediterranean) should be reconsidered. The Mediterranean poor cod T. m. capelanus is more closely related to bib T. luscus than to the Atlantic poor cod, so the population structure in the Atlantic and Mediterranean poor cod must be considered separately. Among 635 Atlantic individuals there was some evidence of poor cod population differentiation (allele frequency heterogeneity test P < 0·0005; FST = 0·0135, P < 0·0005). Levels of genetic variation were similar to those reported for related gadoid species. Some differentiation was present on the Norwegian coast (samples from Trondheimsfjord) and between the Faeroe Islands (Faeroe Bank) and the adjacent European coastal location. In contrast no statistically significant population differentiation was evident in Mediterranean poor cod, but ...

Aquaculture Environment Interactions, 2012

The culture of certain fish species to sizes at which they can reproduce has led to the escape of... more The culture of certain fish species to sizes at which they can reproduce has led to the escape of fertilised eggs or 'escape through spawning'. To investigate the extent and ecological importance of spawning in sea-cages for Atlantic cod Gadus morhua (L.), we (1) evaluated the extent, frequency and timing of spawning in cod culture; (2) analysed the quality of eggs released from farms in terms of variation in fatty acids; (3) modelled the distribution of eggs and larvae from a commercial cod culture site; and (4) predicted the post-escape survival of eggs through summarizing existing knowledge on survival rates of different life stages. Collectively, our results indicate that cod farming has the potential to produce large amounts of eggs and larvae through spawning in cages, with numbers of eggs spawned being 4 to 5 times higher in the second than in the first year. Our scenarios suggest that a typical sea-cage with 60 000 fish may produce 1.4 to 21 tons of 3 yr old first generation farmed cod through spawning in sea-cages. The quality of escaped eggs and larvae is likely to be sufficient for larvae to survive until the first feeding, while survival until adulthood, though difficult to predict, may be high under favourable conditions. Simulations indicate that eggs and larvae from farms may mix with those of wild fish during the spawning season, and thus experience comparable larval environments. However, several implementable management measures exist that will diminish the extent of egg escape in future cod farming.

Toxicon, 2010

The venom of Antarctic octopus remains completely unstudied. Here, a preliminary investigation wa... more The venom of Antarctic octopus remains completely unstudied. Here, a preliminary investigation was conducted into the properties of posterior salivary gland (PSG) extracts from four Antarctica eledonine (Incirrata; Octopodidae) species (Adelieledone polymorpha, Megaleledone setebos, Pareledone aequipapillae, and Pareledone turqueti) collected from the coast off George V's Land, Antarctica. Specimens were assayed for alkaline phosphatase (ALP), acetylcholinesterase (AChE), proteolytic, phospholipase A 2 (PLA 2 ), and haemolytic activities. For comparison, stomach tissue from Cirroctopus sp. (Cirrata; Cirroctopodidae) was also assayed for ALP, AChE, proteolytic and haemolytic activities. Dietary and morphological data were collected from the literature to explore the ecological importance of venom, taking an adaptive evolutionary approach. Of the incirrate species, three showed activities in all assays, while P. turqueti did not exhibit any haemolytic activity. There was evidence for cold-adaptation of ALP in all incirrates, while proteolytic activity in all except P. turqueti. Cirroctopus sp. stomach tissue extract showed ALP, AChE and some proteolytic activity. It was concluded that the AChE activity seen in the PSG extracts was possibly due to a release of household proteins, and not one of the secreted salivary toxins. Although venom undoubtedly plays an important part in prey capture and processing by Antarctica eledonines, no obvious adaptations to differences in diet or morphology were apparent from the enzymatic and haemolytic assays. However, several morphological features including enlarged PSG, small buccal mass, and small beak suggest such adaptations are present. Future studies should be conducted on several levels: Venomic, providing more detailed information on the venom compositions as well as the venom components themselves; ecological, for example application of serological or genetic methods in identifying stomach contents; and behavioural, including observations on capture of different types of prey.

Journal of the Marine Biological Association of the United Kingdom, 1998

... Cemal Turan a1 , Gary R. Carvalho a1 c1 and Jarle Mork a2. ... Monte-Carlo % 2 analysis of ha... more ... Cemal Turan a1 , Gary R. Carvalho a1 c1 and Jarle Mork a2. ... Monte-Carlo % 2 analysis of haplotype frequencies revealed no significant geographic heterogeneity among samples, thus revealing a discordant pattern of genetic differentiation produced by allozymes and mtDNA ...

New Zealand Journal of Marine and Freshwater Research, 2002

The southern blue whiting Micromesistius australis (Norman, 1937) is found in two geographically ... more The southern blue whiting Micromesistius australis (Norman, 1937) is found in two geographically distinct areas, the South Atlantic and south-west Pacific Oceans. To date there has been no appraisal of the genetic relationships between the populations in these two areas. Here, we present ...

Molecular Ecology, 2003

A total of 1290 cod ( Gadus morhua L.), sampled between 1985 and 1999 from a spawning area in the... more A total of 1290 cod ( Gadus morhua L.), sampled between 1985 and 1999 from a spawning area in the Trondheimsfjord, Norway, were assayed for the nuclear-encoded locus Pan I ( pantophysin). The majority of samples were taken during the spawning season at two nearby sampling locations at depths of 100 and 60 m, respectively. Genetic analysis revealed significant effects of cohort, sex and sampling location on allele frequencies at Pan I. The contribution of each of these three factors to the total among-sample diversity ( F ST ) of 8.01% at Pan I was estimated to be 3.78, 2.55 and 1.68%, respectively. Sign tests revealed a significant excess of heterozygotes at both sampling locations in females; a significant excess of heterozygotes in males was observed at one of the localities. Mutation, genetic drift and immigration do not appear to contribute significantly to the observed genetic heterogeneity at Pan I, leaving natural selection as the main explanatory factor for the Hardy-Weinberg imbalance. The dynamics of the selection at Pan I appear to be complex. Analysis of age, sex and cohort proved crucial to disentangle putative explanatory factors from their secondary effects.

Marine Policy, 2014

ABSTRACT The following article outlines of an assessment of the adaptive capacity of stakeholder ... more ABSTRACT The following article outlines of an assessment of the adaptive capacity of stakeholder groups in the Trondheimsfjord region to the impacts related to local changes in Periphylla periphylla (jellyfish) concentrations. This paper addresses the interaction between the socio-ecological system and the marine ecosystem and the management challenges inherent therein by focusing on a serious management problem that is occurring in several Norwegian fjords. This is the recent superabundance of the lower trophic level jellyfish species P. periphylla, which competes with commercial Norwegian fish species for a wide variety of pelagic organisms including redfeed (Calanus finmarchicus), a key species in the coastal ecosystem and a particularly important food item for all codfishes in coastal waters. P. periphylla has, however, also some properties that might make it a valuable new resource in Norwegian waters, namely its potential for being a new and abundant source of collagen. The question addressed here is how to manage this jellyfish species in a manner that is rational from both socio-political and ecological perspectives, exploring stakeholder perceptions concerning their adaptation options and capacity to implement these options to this new resource and management mitigation options based on a set of stakeholder driven future scenarios.

Journal of Fish Biology, 1995

ABSTRACT Genetic variation in blue whiting Micromesistius poutassou was investigated by starch ge... more ABSTRACT Genetic variation in blue whiting Micromesistius poutassou was investigated by starch gel electrophoresis of enzymes in tissue extracts. A total of 130 specimens from the spawning areas west of the British Isles were collected from trawl catches in 1990 (n= 30) and 1992 (n= 100). In 25 tissue enzyme loci screened for genetic variants in the 1990 sample, polymorphisms (0.95 criterion) were found at IDDH-2*, IDHP-2* and PGM-1*, giving a frequency of polymorphic loci of P0.95= 0.12. In pooled samples the average heterozygosity per locus was estimated at He=0.043 and the effective number of alleles per locus at 2.20, 1.45 and 1.53, respectively, for IDDH-2*, IDHP-2* and PGM-1*.