Iceland Marine Research Institute

Reykjavik, Iceland

Iceland Marine Research Institute

Reykjavik, Iceland
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Jonsdottir I.G.,Iceland Marine Research Institute
Marine Biology Research | Year: 2017

Northern shrimp (Pandalus borealis) is targeted by commercial fisheries, but is also an important prey in the marine food web. In this study, stomach content data were used to study predation on shrimp by three gadoid species, cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus), in six inshore areas around Iceland. The results showed that shrimp was more important in the diet of cod compared with the other two predators. However, the overall predation pressure was similar for cod and haddock due to the high abundance of haddock. Therefore, even though shrimp is not the primary source of food for haddock, this species can have a substantial effect on shrimp stocks when haddock abundance is high. In addition, while cod and haddock did not select for any particular size of shrimp, whiting seemed to preferentially target juvenile shrimp. The results suggest that due to the overall effects of these three predators on shrimp stocks, gadoids need to be included in the management of shrimp stocks as predation is one of the major drivers in the development of this important prey stock. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Biological data were retrieved from 374 female Atlantic wolffish (Anarhichas lupus) collected from 2001–2006 at A. lupus main spawning grounds in Iceland and at two other locations with different sea temperature regimes to investigate spatial and temporal difference in fecundity and indications of atresia. There was no spatial difference in fecundity but temporal difference was found, and fecundity decreased in time, clearly indicating the presence of atresia. A. lupus that was 57 cm long was 11% more fecund in the year 2003 than in 2005. Egg numbers decreased about 20% from June to October for 67 cm long A. lupus. There was a positive relationship between fecundity and condition of the fish. © 2017 Elsevier B.V.

Olafsdottir D.,Iceland Marine Research Institute | Shinn A.P.,University of Stirling
Parasites and Vectors | Year: 2013

Background: Whilst there is a body of scientific literature relating to the epibiotic macrofauna on large whales, there is little information on the cetaceans in Icelandic waters. Common minke whales, Balaenoptera acutorostrata Lacépède, 1804, are a common sighting between the months of April to November, however, the migration and distribution of the population in winter requires establishing. The present study provides baseline information on the species composition, geographic distribution and abundance of the epibiotic macrofauna on minke whales landed in Icelandic waters and comments on their acquisition. Methods. The epibiotic macrofauna and skin lesions on 185 and 188 common minke whales respectively, landed in Icelandic waters between April to September 2003-2007 were determined. For each whale, the fluke and one lateral side was examined. Results: A total of seven epibiotic species were found: the caligid copepod Caligus elongatus (prevalence (P) = 11.9%, mean intensity (M.I) = 95.5); the pennellid copepod Pennella balaenopterae (P = 10.3%, M.I = 1.6); the cyamid amphipod Cyamus balaenopterae (P = 6.5%, M.I = 37.0); the lepadid cirripedes Conchoderma virgatum (P = 0.5%, M.I = 4.0) and Conchoderma auritum (P = 0.5%, M.I = 1.0), the balanid cirriped Xenobalanus globicipitis (P = 1.6%, M.I = 5.3) and the sea lamprey Petromyzon marinus (P = 2.7%, M.I = 1.0). In addition, the hyperparasitic monogenean Udonella caligorum was found on C. elongatus (P = 6.6%) on 8 of the 22 whales infected with the copepod. No significant relationship was observed between parasite intensity and host body length for either C. balaenopterae or C. elongatus, while the proportion of infected hosts was higher in August-September than earlier in the summer for C. balaenopterae (χ2 = 13.69; p<0.01: d.f.=1) and C. elongatus (χ2 = 28.88; p<0.01: d.f.=1). Conclusions: The higher prevalence of C. balaenopterae on male whales (χ2 = 5.08; p<0.05: d.f.=1), suggests possible different migration routes by the sexes. A likely explanation of the occurrence of P. marinus attached to the minke whales may be due to the gradually rising sea temperature in the area in recent years. This study represents the first known record of C. elongatus on a cetacean host. © 2013 Ólafsdóttir and Shinn; licensee BioMed Central Ltd.

Carscadden J.E.,Northwest Atlantic Fisheries Center | Gjosaeter H.,Norwegian Institute of Marine Research | Vilhjalmsson H.,Iceland Marine Research Institute
Progress in Oceanography | Year: 2013

Capelin stocks in the Barents Sea, around Iceland and off eastern Newfoundland and Labrador have traditionally undergone similar basic migration patterns, from southern spawning sites to more northern feeding locations. In this paper, the migration and distribution patterns are reviewed for the three stocks. Special attention is paid to the relatively recent past, when Icelandic and Newfoundland/Labrador stocks exhibited changes in these patterns, while the Barents Sea stock did not undergo any significant distributional change. The changes occurred first off Newfoundland/Labrador and later in Icelandic waters. We examine the possible role of temperature and stock abundance in controlling capelin migration and distribution through comparisons of the three stocks. From the available observations, it is not possible to determine the relative impacts of temperature and abundance. However, all three areas have exhibited significant warming trend and we suggest that capelin may be reacting to large-scale ocean climate changes that have been occurring in the Arctic as a result of global warming. We speculate that such changes should appear first off Newfoundland/Labrador because this area is more heavily dominated by waters from the Arctic. In contrast, while both the Barents Sea and Icelandic areas are influenced by waters of Arctic origin, they also receive a significant input of warmer, Atlantic waters. The appearance of capelin in the Canadian Arctic is consistent with the movement towards the Arctic and/or an increase in abundance of a subarctic species previously at the margins of its historical distribution, under conditions of increasing ocean temperatures in the Arctic. © 2013.

Carscadden J.E.,Northwest Atlantic Fisheries Center | Gjosaeter H.,Norwegian Institute of Marine Research | Vilhjalmsson H.,Iceland Marine Research Institute
Progress in Oceanography | Year: 2013

Capelin (Mallotus villosus) is a short-lived, coldwater, pelagic species that occurs in large populations in the Barents Sea, around Iceland and in the Newfoundland-Labrador area in the North Atlantic. Most individuals spawn only once at age three or four and die shortly after spawning. The commercial fisheries for capelin in the three areas are prosecuted on the pre-spawning and spawning age groups and knowledge of recruitment to the spawning stock and factors affecting recruitment are important in the management of the fisheries. Herein, we review the state of knowledge regarding recruitment in the three areas and factors that affect recruitment. Year class strength of capelin is fixed fairly early in life; at 0-group stage in the Barents Sea, by age 1 or earlier for Icelandic capelin, and within 2. weeks of hatching for the beach spawners in the Newfoundland area. No obvious single factor, common to the three stocks, has been proven to exert a significant influence on recruitment. In the Barents Sea, juvenile herring prey heavily on capelin larvae and when the estimates of the abundance of these juvenile herring were accounted for in the capelin stock-recruitment analysis, the fit in the stock-recruitment relationship improved. In Iceland, there is no reason to implicate predation as a dominant factor, although detailed studies have not been carried out. In the Newfoundland and Labrador area earlier studies suggested two factors were important for recruitment success: the frequency of onshore winds at a critical period during the residence of newly hatched larvae in the beach gravel and the presence of warm waters during the early larval phase in the pelagic environment. With further testing using more data, the temperature factor was found not to be significant but the frequency of onshore winds still explained a significant portion of the variation in year class strength. There appears to be no significant biological influence, such as predation, that has influenced recruitment in this area. © 2013.

Magnusson A.,University of Washington | Magnusson A.,Iceland Marine Research Institute | Punt A.E.,University of Washington | Hilborn R.,University of Washington
Fish and Fisheries | Year: 2013

Fisheries management depends on reliable quantification of uncertainty for decision-making. We evaluate which uncertainty method can be expected to perform best for fisheries stock assessment. The method should generate confidence intervals that are neither too narrow nor too wide, in order to cover the true value of estimated quantities with a probability matching the claimed confidence level. This simulation study compares the performance of the delta method, the bootstrap, and Markov chain Monte Carlo (MCMC). A statistical catch-at-age model is fitted to 1000 simulated datasets, with varying recruitment and observation noise. Six reference points are estimated, and confidence intervals are constructed across a range of significance levels. Overall, the delta method and MCMC performed considerably better than the bootstrap, and MCMC was the most reliable method in terms of worst-case performance, for our relatively data-rich scenario and catch-at-age model, which was not subject to substantial model misspecification. All three methods generated too narrow confidence intervals, underestimating the true uncertainty. Bias correction improved the bootstrap performance, but not enough to match the performance of the delta method and MCMC. We recommend using MCMC as the default method for quantifying uncertainty in fisheries stock assessment, although the delta method is the fastest to apply, and the bootstrap is useful to diagnose estimator bias. © 2012 John Wiley & Sons Ltd.

Gudmundsson G.,University of Iceland | Gunnlaugsson T.,Iceland Marine Research Institute
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2012

Fish stock assessment by catch-at-age and survey data is affected by many stochastic elements: measurement errors; sampling variations; natural variations in mortality, catchability and migrations; technological and social effects on fishing intensity and selectivity. Estimation of simulated models shows that the bias in estimation by linear approximation of the Kalman filter or automatic approximation of the marginal likelihood function is much smaller than the errors produced by the stochastic elements. In time series modelling, they are represented by residuals in the equations. Strong simplifying assumptions about these effects are common in catch-at-age analysis, but estimation of models for Icelandic cod (Gadus morhua) and pollock (Pollachius virens, herein referred to as saithe) demonstrates that the relative importance of different random elements can vary greatly between stocks. These assumptions include exact catch-at-age measurements, no irregular migrations or variations in natural mortality, separable fishing mortality rates, and no permanent variations in survey catchability. Inappropriate simplificactions can have a strong effect on stock estimates. It is possible and important to test simplifying assumptions by comparison with more general models. Estimation of the magnitude of natural mortality is also examined.

Jnsson S.,University of Akureyri | Valdimarsson H.,Iceland Marine Research Institute
ICES Journal of Marine Science | Year: 2012

In the Denmark Strait between Greenland and Iceland, the north-flowing warm, saline Atlantic Water (AW) of the Irminger Current meets the south-flowing cold, relatively fresh Polar Water (PW) of the East Greenland Current. A mixture of these two surface water masses then flows along the shelf north of Iceland. The mixture can vary from being almost pure AW to consisting, to a large extent, of PW. The relative quantities of each water mass to some extent determine the productivity and the living conditions on the shelf north of Iceland. The flow has been monitored with current meters on a section north of Iceland since 1994, and these measurements, together with hydrographic data, are used to study its structure and variability. The amount of AW carried by the flow is calculated along with the associated heat transport. In the period 19942010, the flow consisted on average of 68 of AW with a transport of 0.88 Sv and an associated heat transport of 24 TW. There is notable seasonal variation in the flow and strong interannual variability. © 2012 International Council for the Exploration of the Sea.

Palsson O.K.,Iceland Marine Research Institute | Bjrnsson H.,Iceland Marine Research Institute
ICES Journal of Marine Science | Year: 2011

Data on the diet composition of Iceland cod (Gadus morhua) were collected in March of the years 19812010 and in autumn of the years 19882010. Capelin, northern shrimp, and euphausiids dominate the diet in all years and may be classified as the stable food of Iceland cod. Overall, total consumption by the smallest cod (2029 cm) remained stable over the three decades, whereas that of larger fish has declined since the mid-1990s. This decline may explain the reduced growth rate of cod in recent years. Long-term, prey-specific patterns were identified in consumption, and significant trophic links were found between cod consumption and stock sizes of capelin and northern shrimp. In March, the correlation between cod consumption on capelin and capelin stock size was highly significant, a type I functional feeding response, but not significant in autumn. The correlation deteriorated in the early to mid-1990s and in the early 2000s. Increased inflow of Atlantic water into north Icelandic waters, and associated changes in capelin distribution, may have contributed to this trend. The interaction between cod consumption on northern shrimp and shrimp stock size showed a highly significant type I functional feeding response in both seasons. © 2011 International Council for the Exploration of the Sea.

Bjornsson B.,Iceland Marine Research Institute
Aquaculture | Year: 2011

Anthropogenic feeding was carried out for 21months in a fjord in Northwest Iceland to assess the potential of aggregating and growing free-ranging cod (Gadus morhua). Practical feeding and harvesting methods were developed and four sizable herds of wild cod formed at four feeding stations, where net bags with frozen trash fish were deployed 2-5 times per week. Commercial fishing was prohibited in a 30km2 area around the feeding stations, where a total of 262 metric tons (t) of feed was dispensed. In August 2005, when the monthly feeding peaked at 27.2t, the biomass of cod in the herds was estimated to be 70-100t, mainly fish >40cm. The biomass of cod in the fjord was estimated as approximately 2000t. The conditioned fish showed high fidelity to a given herd and their growth rates approximately tripled. A total of 171t of cod and 82t of haddock (Melanogrammus aeglefinus) were harvested in the project. Ranching of cod in herds has the potential of reducing the cost and energy consumption of fishing, and on-growing wild cod on a large scale without the cost associated with sea cages. © 2010 Elsevier B.V.

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