Below you will find 4 different student projects that combine fisheries science and marine ecology in various ways

Transcription

1 Below you will find 4 different student projects that combine fisheries science and marine ecology in various ways

2 PROJECT #1: How much forage fish do fisheries need to leave in the sea to support ecosystem services? Is one third for the bird enough? Fishing for forage-fishes is subject to major criticism, and for good reasons. Forage fishes, given their immense biomass, are the primary linkage between lower and higher trophic levels. Removing forage fish biomass could potentially result in shorter food chains and reduced biomass at the highest trophic levels, unless we are capable of fishing at or near maximum sustainable yield where fishing is assumed to release density dependent mechanisms an increase productivity. It is currently debated what is the optimal management strategy and whether we can apply rules of thumb as proposed in a recent NATURE paper stating that one third of the forage fish biomass should be left for the birds. Below we have identified two student projects: [1] Reviewing and evaluating management strategies and reference points applied to forage fishes all over the world. This is urgently needed! [2] Energy conversion efficiency of forage-fishes is an important ecological aspect of the food-web, and has been proposed as a major determinant of food-chain length (the energy-flow hypothesis) and predator production. Currently, conversion efficiency is not considered in fishery management context. Perhaps we need to change that. The energy conversion efficiency is often presented as a standardized value given for an individual for the purpose of comparison. We need the student to explore, using modelling techniques, how the ecologically effective conversion efficiency depends on zooplankton seasonality and species composition, age structure of forage fish populations, and seasonality in fishing mortality and natural mortality. If you are interested in more information about the above projects please contact: Anna Rindorf (head of section for ecosystem based management), mail ar@aqua.dtu.dk or Mikael van Deurs on mobile , mail mvd@aqua.dtu.dk or Asbjørn Christensen, mail ar@aqua.dtu.dk

3 PROJECT #2: DO YOU WANT TO MAKE A DIFFERENCE IN HOW WE MANAGE A BILLION DOLLAR INDUSTRY (SANDEEL)? Addressing current issues in relation to stock assessments for short lived species [1] Our current advice for Lesser sandeel is based on a model that assumes that Lesser sandeel are highly resident by nature and that all dispersion therefore occurs during the larval phase. Is this assumption correct? How do we track fish that are too small to be tagged with current technologies? Could otolith-microstructure be the answer? Or should we instead innovate the tagging technology? [2] For short lived species such as Lesser sandeel and sprat, the short term forecast on which the advice is based is no better than the accuracy of the predictions of the incoming year-class (recruitment). We are therefore constantly looking for ways of advancing recruitment indices. It turns out that the annual herring larvae sampling program is catching considerable numbers of other fish larvae that are currently not used for anything. Could they be used to improve our advice for these species? (alternatively the student can help us develop an image recognition methodology to help us identifying sandeel larvae) [1] Sprat spawns multiple times during the summer period. This is not accounted for in the stock assessment model where spawning is fixed on July 1. However, to improve the model we need more knowledge on how spawning is distributed over time, and whether spawning time affects larval survival and age-at-maturity. Otolith micro-structure analysis is the key to answering these questions (the project could alternatively be about developing new technologies/methodologies for speeding up microstructure-analyses, which is urgently needed). If you are interested in more information about the above projects please contact: Henrik Mosegaard (Prof. And head of section for marine living resources), mail hm@aqua.dtu.dk or Michael van Deurs (Post Doc) on mobile , mail mvd@aqua.dtu.dk

4 PROJECT #3: Can knowledge about sandeel ecology be used to optimize its economic value? Between and 1 million tons of sandeel is landed in the North Sea every year, depending on the fishing quote. These fish are sold to the fish meal industry, where high oil content is priced. Sandeel built up lipid reserves during the fishing season, and the lipid content and composition differs between regions, presumable determined by food quantity and quality. Can we use information about sandeel ecology to help the fishery optimize the oil content in their catches? The industry has handed over a large data-set that holds information about the oil% of individual catches covering large parts of the North Sea and the fishing season. (oil)/(oil+dry-mat) month The figure shows the proportion of oil to dry matter in all industrial landings. If you are interested in hearing more please contact: Henrik Mosegaard (Prof. And head of section for marine living resources), mail hm@aqua.dtu.dk or Michael van Deurs (Post Doc) on mobile , mail mvd@aqua.dtu.dk

5 PROJECT #4: Copepods and fish How will climate induced changes in the copepod communities affect our fish stocks and ultimately the fisheries? Evidence of climate-induced reductions in mean copepod size and shifts in the species composition is coming from both the North Sea and arctic regions. From the perspective of a fish, smaller copepods are in general harder to see and contain fewer lipids. The question is: How is this going to affect our fish stocks? The student will get an opportunity to address this question as she/he dives into a data-set, which is being collected in the North Sea right now. Figure: Copepods from sandeel stomachs. Notice the significant difference in size of the copepods. If you are interested in more information about the above project please contact: Mikael van Deurs on mobile , mail mvd@aqua.dtu.dk or Sigrun Jonasdottir, mail sjo@aqua.dtu.dk