Download Subject 4: Normal blood values in cultured fish species.

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