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BSc thesis subjects AFI July 2014 Subject 1: The role of deposit feeders in Integrated Multi-Trophic Aquaculture (IMTA) Integrated Multi-Trophic Aquaculture (IMTA) is proposed as a sustainable aquaculture system for the future. In IMTA systems the culture of “fed” species (e.g. fish, crab or shrimps) is linked to the culture of “extractive” species (e.g. filter feeders, detritus feeders or autotrophs), with the goal to balance inputs (i.e. nutrients given to fed species) and outputs (i.e. nutrients extracted in the form of fed and extractive species). However, the question can be raised whether balancing the amount of nutrients added to and extracted from the ecosystem in itself guarantees sustainability? Too little is known about nutrient flows in open IMTA systems to answer this question. Fed species only retain 20 - 45% of the nutrients provided through feeding. The other fraction is released as organic and inorganic “wastes”. A part of this released “wastes” settles at the seafloor and can be turned into resources for deposit feeders. However which part of the released “waste” can be retained by the deposit feeders is unknown. In this literature study the possibilities of using deposit feeders in open IMTA systems will be studied. The focus will be on the nutrient retention of deposit feeders and on the methods used to determine this retention. Based on the information obtained options and consequences of integrating deposit feeders in IMTA systems need to be discussed. Supervision: Marit Nederlof & Marc Verdegem Contact: Marc Verdegem ([email protected]) Number of possible students: 1 Subject 2: Bioflocs, the key to feed more with less: is the effect of live or dead bioflocs on gut homeostasis different? The principle of wastewater treatment by bioflocs (BFs) is extensively used in the treatment of domesticand industrial wastewater (activated suspension systems). BFs are highly porous, amorphous aggregations of microorganisms, particles and other constituents held together by extracellular polymeric substances. The use of BFs is a relatively new approach in aquaculture and is referred to as Biofloc Technology (BFT). The BFs are co-cultured with the cultured species and aid in the conversion of organic and inorganic wastes into microbial biomass. Other than facilitating a favourable water quality in the system the BFs also serve as an additional protein source for filter feeders such as shrimp and tilapia. It is known that BFs have a beneficial effect on both shrimp and fish. The exact mechanisms involved leading to the positive effects of Bioflocs on the health and homeostasis in aquaculture species are not yet fully understood. The current study will assess the differentiation in gene expression in the GI-tract of Nile tilapia (Oreochromis niloticus) occurring under high intake of live bacterial Bioflocs in Biofloc Technology systems as compared to intake of the same bacteria but killed and incorporated in a feed as a bacterial-meal. Practical work will start by September 2014. Different BSc thesis projects are possible, ranging between participating in experiments or lab analysis, literature review on specific knowledge gaps and data analysis. Supervision: Marit Nederlof & Marc Verdegem Contact: Marc Verdegem ([email protected]) Number of possible students: 1 Subject 3: Voedselgebruik door invasieve grondels in de IJssel De laatste jaren zijn diverse exotische grondels met een enorme opmars bezig in de Nederlandse binnenwateren, met name in de grote rivieren. Omdat het grootste deel van de Nederlandse wateren wordt doorspoeld met rivierwater, is de verwachting dat deze soorten zich binnen afzienbare tijd in heel Nederland gevestigd hebben. Het gaat met name om Kesslers grondel (sinds 2004), Zwartbekgrondel (sinds 2007) en Pontische stroomgrondel (sinds 2009). Vooral Zwartbekgrondel vormt nu al een belangrijk deel van de totale visfauna in delen van de grote rivieren. Om die reden is door Sportvisserij Nederland in samenwerking met AOC Groene Welle (de Sportvisserijopleiding) uit Zwolle een monitoringproject begonnen om de populatieontwikkeling van deze soorten te volgen. Naast deze monitoring is het belangrijk om de effecten op het voedselweb van deze soorten nader te onderzoeken. Daarom zoekt AFI twee of meer BSc-scriptiestudenten die de darminhouden van gevangen grondels gaan analyseren. De belangrijkste vragen daarbij zijn: 1) Waaruit bestaat het dieet van exotische grondels?; 2) Wat zijn de verschillen tussen de grondelsoorten?; 3) Hoe verandert het dieet met de grootte van de grondels (ontogenetische veranderingen)?; 4) Wat is de invloed van milieuomstandigheden op het dieet? Supervision: Leo Nagelkerke Contact: Leo Nagelkerke ([email protected]) Number of possible students: 1 Subject 4: Normal blood values in cultured fish species. Numerous fish species are cultured and this number is still increasing. Related to new species is often a lack of biological information on these species. For practical fish farmers, measuring simple blood parameters as haematocrit, blood cell counts are used as indicators of health status. In research such parameters are also used to assess the impact of husbandry conditions and nutrition. However, generally there is lack of information what normal blood values are which can be used as simple health indicators for fish. The aim of this BSc subject is to obtain an across fish species comparison on haematological parameters, for getting an indication of normal values for fish. Moreover, the literature study should identify the major factors (nutrition, temperature, life stage) that affect these parameters. The student is asked to perform a literature study to create a data base. Depending on the amount of date obtained statistical analyses for comparing fish species will be considered. The information needs to be presented in a comprehensive report. Supervision and contact: Johan Schrama ([email protected]) Number of possible student subjects: 1 Subject 5: Greenhouse gas emissions from aquaculture ponds Large amounts of formulated food are fed to aquaculture ponds, cages and raceways. The majority of the nutrients applied with the feed become organic waste products which are broken down by microorganisms. The end products of decomposition contribute to CO2, NH3, N2O, etc. gas emissions. The goal of this project is to identify and quantify which gasses escape from aquaculture systems and to identify effects on global warming. Attention needs to be given to the metabolic processes leading to greenhouse gas production in ponds. Work to be done includes 1) a literature search and 2) analysis and summary or the available information with focus on the types and quantities of greenhouse gas emissions from ponds. Supervision and contact:Marc Verdegem & Ep Eding ([email protected]) Number of possible student subjects: 1 Subject 6: Selective fishing, balanced harvesting and sustainability of fisheries and ecosystems: the effects of selective fishing on species and sizes to fish communities. More and more evidence appears that selective fishing on species and sizes to target large, mature fish and avoid by-catch of juvenile fish and non-target species as dolphins or turtles has unexpected side effects on fish populations and fish communities. These range from phenotypic and possibly even genotypic effects (fishery-induced evolution) on size and reproductive capacity of species like cod in the North-Sea to an increase in by-catch of sharks, marlins and other species by avoiding dolphins in tuna fisheries in the Eastern Pacific. The selectivity paradigm in fisheries is 50-year old and turns out not to fit very well in an Ecosystem Approach to fisheries. The paradigm is to avoid catching juveniles and only catch fish when they have grown to commercially optimal sizes. However, it ignores trophic relations and predation and the fact that big old fecund female fish (BOFFF’s) are important to maintain stable reproduction. From model studies it appears that non-selective fisheries, in other words, fisheries that fish the whole fish community and target all sizes and species relative to their production, may maintain ecosystem structure and lead to higher long-term yields. An Ecosystem-Approach to Fisheries requires maintenance of ecosystem structure and processes. In that perspective, selectivity regulations on individual species may diminish rather than enhance the sustainability of the fishery and ecosystem. So the selectivity paradigm needs to be reassessed in an ecosystem perspective! This is a large subject that can be approached in many ways. Specific subjects could be: 1. On by-catch in specific fisheries as the tuna purse seine fisheries; how to assess these in the light of an ecosystem approach? 2. The effects of fishing on juveniles that are discarded? 3. The impact of the ban on discarding by the European Union to force fishers to be more selective? 4. Model based approaches to size selection and what we can learn from those? 5. Fishery induced evolution: has the long term pressure on larger individuals in the plaice fisheries in the North Sea lead to slower growth? And what would that mean for stock recovery now that fishing pressure has reduced? Possible tasks include literature study, data analysis on specific examples from African lakes (Kariba, Mweru), Tuna fisheries in the Western Pacific or the North-Sea Supervision: Paul van Zwieten, Leo Nagelkerke and Adriaan Rijnsdorp can assist in defining the subject further First contact: Paul van Zwieten ([email protected]) Number of possible student subjects: 5 Subject 7: Assess the feasibility of composting the sludge collected from the septic tank of an outdoor water recirculation system for pangasius aquaculture Traditional farming of pangasius uses river water to refresh the pond water, resulting in nutrient disposal to the river. Often, the latter is increased by the pumping of the pond-sediment in the river. In a collaborative project WU-AFI is testing out-door Recirculation Aquaculture systems (RAS) for the pangasius. The RAS has a septic tank where the sludge accumulates. This sludge contains high concentration of N and P that can be used as fertiliser if the water content is low. Composting is one technique to reduce water content. To succeed composting the sludge needs to be mixed with e.g. water hyacinth to increase the N–content, and rice-straw to increase the C-content and improve the structure. The BSc students is expected to calculate the recommended ratio between sludge. water hyacinth and rice straw. Supervision: Roel Bosma First contact: Roel Bosma ([email protected]) Number of possible student subjects: 1