Mattias Sköld

Stem Cells in Asexual Reproduction of Marine Invertebrates

While sexual reproduction is conserved and almost ubiquitous, asexual reproduction in forms of parthenogenesis or agametic cloning from somatic tissue is less conserved. The phylogeny shows that agametic cloning is widespread but scattered with many different modes for asexual formation of a new animal. This suggests that independent forms of cloning have evolved later from sexual ancestors between and within different phyla. Here, we present an overview of agametic cloning in the marine animal kingdom and discuss molecular and evolutionary aspects of somatic stem cell usage for asexual cloning. The molecular tissue characterizations and the relative role of different stem cells involved in agametic cloning are only at its beginning with whole phyla largely uncovered. An emerging hypothesis is that the first somatic stem cells used in cloning were also able to form a germ-line and that the more limited lineage specific stem cells are derived. We discuss advantages and problems with agametic cloning from somatic tissue and propose that the levels of stem cell potential held in the tissue can have large consequences for the reproductive life cycle strategies and long-term fitness in clonal animals and strains. We finally describe suitable molecular experimental approaches for future research on this topic.

Bottom trawling affects fish condition through changes in the ratio of prey availability to density of competitors

This research was supported by FP7 project BENTHIS (312088), FP7 project ASSEMBLE (227799), the Sven Loven Centre for Marine Sciences, Marie Curie Fellowship LINKFISH (299552) and the Swedish Research Council FORMAS (2012-942).

Gender differences in health and aging of Atlantic cod subject to size selective fishery

Summary We have analyzed health and physiological aging parameters in male and female Atlantic cod, Gadus morhua, captured in Kattegat, Skagerrak and in Öresund. Gender differences were clearly evident in a number of variables. Males had longer liver telomeres and higher catalase activities than females, while females had higher superoxide dismutase activity, liver somatic index and condition factor. Effects of age were found for males where levels of the antioxidant glutathione and telomere length declined with age, indicating physiological aging. Liver somatic index increased and percentage oxidized glutathione decreased with age. Between-site comparisons of males show that percentage oxidized glutathione and catalase were lowest in Kattegat, whereas protein carbonyls and condition factor were higher in Skagerrak. Females, on the other hand, showed no differences between sites or indications of somatic aging or age-related effects in egg quality, indicating that older and larger female cod are healthy and show no changes in eggs with age. In contrast, males showed indications of physiological aging and lower condition than females. The results emphasize the importance of conserving old mature fish, in particular high egg-productive females, when managing fisheries.

Stable isotopes reveal the effect of trawl fisheries on the diet of commercially exploited species

Bottom trawling can change food availability for benthivorous demersal species by (i) changing benthic prey composition through physical seabed impacts and (ii) by removing overall benthic consumer biomass increasing the net availability of benthic prey for remaining individuals. Thus trawling may both negatively and positively influence the quantity and quality of food available. Using δ13C and δ15N we investigated potential diet changes of three commercially exploited species across trawling gradients in the Kattegat (plaice, dab and Norway lobster (Nephrops)) and the Irish Sea (Nephrops). In the Kattegat, trawling affected primarily the biomass of benthic consumers, lowering competition. Nephrops showed significant positive relationships for δ13C and a domed relationship for δ15N with trawling. In the Irish Sea, intense trawling had a negative effect on benthic prey. δ13C and δ15N thus showed the inverse relationships to those observed in the Kattegat. Plaice from the Kattegat, showed a significant relationship with trawling intensity for δ13C, but not for δ15N. No relationship was found for dab. Changes of δ13C and δ15N correlated with changes in condition of species. The results show that the removal of demersal competitors and benthos by trawling can change the diets of commercial species, ultimately affecting their body condition.

New policies may call for new approaches: the case of the Swedish Norway lobster (Nephrops norvegicus) fisheries in the Kattegat and Skagerrak

&NA; The European Common Fisheries Policy has in its 2013 reform increased in complexity, such as a call for coherence with the Marine Strategy Framework Directive and a landing obligation, posing new requirements and challenges to managers, scientists and the fishing industry. Therefore, re‐evaluations of current practice are important as a basis for management actions. The Swedish fishery for Norway lobster (Nephrops norvegicus) in the Kattegat‐Skagerrak area provides an interesting case study of relevance to emerging policies. Sprung from an unbalance in available fish‐ and Nephrops quotas and an ambition to protect coastal areas, the current fishery has been directed towards three separate fisheries (mixed trawling, directed trawling using a sorting grid and creeling). Studying direct and indirect effects from alternative Swedish quota allocations among gear types is therefore interesting. Accordingly, a screening study was conducted, taking into consideration area‐gear interactions in catch rates, to compare the three different fisheries regarding quantified pressures on the target species, the by‐catch species, and on the seafloor, as well as to qualitatively discuss social and economic dimensions. In the next step, alternative quota allocations were studied. In Swedish fisheries, we show that creeling offers a substantial reduction of fishing mortality of both undersized Nephrops and fish and a reduced seafloor pressure per landed kilo of Nephrops. Given that the fishing areas in many cases may be interchangeable between gears, allocating a larger quota share to creels in the Swedish fishery would therefore contribute to the integration of fisheries‐ and environmental management as called for in the new policies.

Distribution and fate of trawling-induced suspension of sediments in a marine protected area

Distribution and fate of trawling-induced suspension of sediments in a marine protected area Torsten Linders*, Per Nilsson, Andreas Wikström, and Mattias Sköld Department of Marine Sciences, University of Gothenburg, Box 461, S-405 30 Gothenburg, Sweden Department of Marine Sciences, University of Gothenburg, 452 96 Strömstad, Sweden Department of Aquatic Resources, Institute of Marine Research, Swedish University of Agricultural Science, Turistgatan 5, S-453 30 Lysekil, Sweden *Corresponding author: tel: þ46 31 7862873; fax: þ46 31 7862560; e-mail: torsten.linders@marine.gu.se