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  • 11
    Publication Date: 2019-09-23
    Type: Report , NonPeerReviewed
    Format: text
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  • 12
    Publication Date: 2016-11-30
    Description: We studied the combined direct physiological and indirect food web effects of ocean acidification on herring larvae inside pelagic mesocosms. A natural plankton community of the Gullmarsfjord, Sweden was enclosed in the Kiel Off-Shore Mesocosms for future Ocean Simulations (KOSMOS) for 113 days from March to June 2013 at ambient and projected end-of-the-century CO2 levels (~760 µatm pCO2). Herring eggs were introduced into the mesocosms, where they hatched in mid of May. The larvae developed inside the mesocosms for ~6 weeks, feeding on prey organisms that experienced treatment CO2 levels for ~9 weeks. This video is meant as an illustration of the herring larvae«s performance inside our mesocosm units.
    Type: Video , NonPeerReviewed
    Format: video
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  • 13
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    GEOMAR
    In:  [Poster] In: ICES Symposium: Challenging the scientific legacy of Johan Hjort: time for a new paradigm in marine research?, 12.-14.06.2019, Bergen, Norway .
    Publication Date: 2019-12-13
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 14
    Publication Date: 2023-02-08
    Description: Cape anchovy Engraulis encrasicolus is an ecologically and economically important pelagic fish species occurring along the coast of South Africa. A recent eastward shift in Cape anchovy distribution indicates that environmental conditions are becoming more favorable for the species on the east coast. This shift is particularly important in the sheltered Algoa Bay region, a nursery area for fish larvae. However, the relatively low productivity of the Agulhas Current Large Marine Ecosystem on the eastern coast of South Africa may result in an anchovy population in poorer nutritional condition and with slower growth rates than the west coast population. Using otolith and nucleic acid analyses, the growth rates of anchovy larvae from the western and southeastern coasts of South Africa were compared. The otolith analysis results indicated that, at any given age, individual growth rates for anchovy larvae were higher on the southeast coast than on the west coast. The RNA:DNA values also indicated that instantaneous growth rates of anchovy larvae were higher in Algoa Bay than on the west coast. At the time of sampling, chlorophyll and zooplankton productivity were higher at sampling sites in Algoa Bay than sites on the west coast, potentially due to favorable oceanographic features in the bay. As such, the results suggest that Algoa Bay is a suitable and potentially favorable nursery area for the early stages of anchovy, highlighting the importance of separate management of the southeast coast region in a changing world.
    Type: Article , PeerReviewed
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  • 15
    Publication Date: 2018-05-08
    Description: Cod larvae from laboratory rearing experiments aged from 1 to 12 d after hatching, both fed and deprived of food, were analysed. The number of increments on the otolith and the width of these increments were determined together with the RNA/DNA ratios on the same individual larva. Alizarin marking of the otoliths was performed to confirm the formation of daily increments. Cod larvae reared at 6*C formed the first ring right after hatching and deposited increments on a daily basis. A comparison of the measurements between the right and the left lapillus showed that these can differ, if the radius is taken. The lapillae core showed especially high individual variability, whereas the sum of the increments did not differ between both lapilli. Until Day 10 after hatching, while the larvae were still feeding on their yolk, the external food situation did not affect the increment width of the lapilli or the RNA/DNA ratios. In larvae older than 10 d the width of the daily increments was dependent on the nutritional situation and RNA/DNA ratios decreased in starving larvae in comparison to feeding larvae. RNA/DNA ratios and increment widths were correlated.
    Type: Article , PeerReviewed
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  • 16
    Publication Date: 2018-05-31
    Description: Eggs and larvae of Baltic sprat Sprattus sprattus L. were collected during 14 cruises covering the spawning season in 2002 in Bornholm Basin. Main egg and larval production was in April, with a second small peak in June 2002. The in situ larval abundance was corrected for transport processes by hydrodynamic model runs. Corrected larval abundance estimates were compared to initial larval production to derive an index of larval mortality. This index suggested a much higher survival of summer- over spring-born sprat larvae, with pronounced differences in survival for larvae 〉11 mm. Independent evidence for this survival pattern was gained by measured RNA:DNA ratios in sprat larvae hatched from April to July 2002 and was linked to temporal variability in potential prey abundance. We found higher mean but less variable RNA:DNA ratios in spring- than in summer-born larvae, indicating a strong selection for fast growth in April and May but a less selective environment in June and July. Zooplankton data revealed high naupliar concentrations of Acartia spp. (a key dietary component of sprat) in April and May, but very low concentrations of larger prey items such as copepodites or adults. In contrast, abundance of larger prey increased considerably in June and July. The results suggest that larger sprat (〉11 mm) in April and May 2002 may have been food limited and, therefore, had lower rates of survival, supporting the underlying hypothesis of size-specific, temporally limited ‘windows of survival’ linked to the availability of suitable prey.
    Type: Article , PeerReviewed
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  • 17
    Publication Date: 2018-06-01
    Description: Weight-specific growth rate (G) and growth performance (the fraction of maximum growth realized, G pf) are key demographic characteristics. The ratio of RNA/DNA (RD) can provide information on both G and G pf. Estimating G from RD in larval fish requires an adjustment for the activity of RNA at different temperatures. Based on a meta-analysis of published data, we present a general model for the relationship between G in marine fish larvae and fluorometrically derived RD and temperature (T), and suggest that this model can be used to estimate G in marine fish larvae. Several options for estimating G pf are also considered, including the use of a reference growth rate (Gref). RDs of well-fed larvae appeared to be independent of water temperatures between 4 and 28°C, suggesting that any increase in growth rate with temperature was accomplished by increased activity rather than increased concentrations of RNA. However, for the best-fit meta-analysis RD–T–G model, the relationship between RD and G pf was temperature dependent for fish less than fully fed.
    Type: Article , PeerReviewed
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  • 18
    Publication Date: 2024-02-07
    Description: The Asian shore crab Hemigrapsus takanoi, native to the northwest Pacific Ocean, was recently discovered in Kiel Fjord (southwestern Baltic Sea). In laboratory experiments, we tested the salinity tolerance of H. takanoi across 8 levels (0 to 35) and across 3 life history stages (larvae, juveniles and adults) to assess its potential to invade the brackish Baltic Sea. Larval development at different salinities was monitored from hatching to the megalopa stage, while survival and feeding of juveniles and adults were assessed over 17 d. Larvae of H. takanoi were able to complete their development to megalopa at salinities 〉= 20 and the time needed after hatch to reach this stage did not differ between salinities of 20, 25, 30 and 35. At a salinity of 15, larvae still reached the last zoea stage (zoea V), but development to the megalopa stage was not completed. All juveniles and adults survived at salinities from 5 to 35. Feeding rates of juveniles increased with increasing salinity across the entire salinity range. However, feeding rates of adults reached their maximum between salinities of 15 and 35. Our results indicate that both juveniles and adults of H. takanoi are euryhaline and can tolerate a wide range of salinities, at least for the time period tested (2 wk). However, larval development was impaired at salinities lower than 20, which may prevent the spread of H. takanoi into the Baltic Proper.
    Type: Article , PeerReviewed
    Format: text
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