Eggs of the copepod Acartia tonsa Dana require hypoxic conditions to tolerate prolonged embryonic development arrest

Additional file 1. Raw data and calculations for all experiments as well as an overview of experiments in this study

The key fisher project:a citizen science programme to monitor Danish coastal fishes

Standardised monitoring of marine species and their populations is important for fisheries management. However, implementing monitoring programmes require extensive resources. In Denmark, a portion of the income obtained from the angling and recreational fishing license is supporting several scientific projects in fresh and coastal marine environment, including stocking, restoration and monitoring. This is known as Fiskepleje. The Key Fisher Project (Nøglefiskerprojektet) is a citizen science programme that has been monitoring the Danish coastal zone for 20 years, supported by Fiskepleje, where no other official monitoring is in place. Each month, recreational fishers deploy standardised gear on fixed positions along the Danish coasts and inside the fjords where they register the fish catches, as a proxy for fish assemblages in the area. The Key Fisher Project is a successful example of how a long-term citizen science programme can contribute to the monitoring of coastal fish stocks in an efficient and cost- effective manner, providing important time-series data on coastal fish assemblages

Habitat restoration and protection effects on european lobsters (<i>Homarus gammarus</i>):the livø stone reef marine protected area, Limfjorden

The Limfjorden has a significant European lobster (Homarus gammarus) population since the mid- 2000’s, following 4 decades of being virtually absent, supporting the largest Danish lobster fishery currently at 45 tonnes and 7 Mio.kr. per year, with significant economic and cultural value to local coastal communities. The Livø stone reefs (LR) were established in 2016 to restore a rare, degraded habitat and associated ecosystem services. A small, protected area (MPA) surrounding the reefs and closed to fishing was created in 2018. The effects of the LR-MPA on lobsters by providing rare reef habitat as well as fishing protection, were evaluated in 2021. Higher abundance, larger sizes and increased reproductive potential were observed in the LR-MPA relative to fished areas, as well as indication of sex specific habitat and protection effects. Lobsters showed high-site fidelity, occasionally with significant movements between LR-MPA and adjacent non-MPA areas. A clear positive effect of LR-MPA on the lobster population was thus observed after only 3 years since its implementation, likely resulting from increased survival and growth but also immigration and retention of large lobsters

Development of a Broodstock Diet to Improve Developmental Competence of Embryos in European Eel, Anguilla Anguilla

International audienceWe examined the effect of dietary arachidonic acid (ARA) and eicosapentaenoic acid (EPA) on the production of embryos and hatched larvae in the European eel, Anguilla anguilla. Two diets with high and intermediate levels of ARA and low and intermediate levels of EPA (Feed 1: ARA 1.9%, EPA 4.2%; Feed 2: ARA 1.2%, EPA 5.1% of total fatty acids) were tested against a commercial diet (DE: ARA: 0.5%, EPA: 8.2% of total fatty acids). After 24 weeks of feeding, ARA levels in the muscles and ovaries increased to 0.9% and 1.3% of total fatty acids, respectively, in Feed 1 and were significantly higher than in Feed 2 and DE. Female broodstock was not fed during hormonal treatment to induce vitellogenesis and ovulation. EPA levels in females fed the test diets decreased in the both muscle and ovary and were significantly lower in eggs from females fed Feed 1. The highest percentage of stripped females, producing viable eggs and larvae, were those females fed the highest dietary ARA levels (Feed 1). The level of lipid peroxidation products in eggs was similar among treatment, indicating that the lowest dietary levels of vitamin C and vitamin E were sufficient. In the unfertilized eggs, ARA levels were also highest (1.1% of total fatty acids) in the diet with highest ARA levels (Feed 1)