Aquaculture projects

Spatial and temporal variations of zooplankton and phytoplankton quantity and quality within a mussel farm: implication for mussel spat collection for aquaculture (special course)

Quality of spat collectors can vary within the same farm from one week to another due to intense biofouling. Weekly monitoring is not capturing the full range of zooplankton present in the water due to the potentially different strategies of organisms in their larval release timing. Farmers need a reliable methodology of monitoring the water in order to place their spat collectors at the appropriate time to target mussel larvae only and keep the collectors fouled-free. The aim of the project is to describe and analyse the variation in mussel larvae density and potential biofouling threats such as ascidian larvae. Compare the zooplankton composition to the phytoplankton distribution within a mussel farm where spat collectors are placed. Within the project FOMUS, weekly monitoring of water and phytoplankton quality has taken place in the Limfjorden since April 2014. Mussel spat collection season starts from end of April beginning of May until the end of June. During the early period of the spat collection season, an intensive monitoring with hourly measurements of the water column will take place within a mussel farm. Time-series of zooplankton composition associated with phytoplankton will be analysed and compared with the settlement of the larvae on spat collectors placed at the same time. A direct application of the results will be some guidance to the mussel farmers to optimize the deployment of spat collectors within a farm. The experiments will be carried out at the Danish Shellfish Centre, Nykøbing Mors. Duration: 1-2 months (5-10 ECTS) between end of April – beginning of June 2016.

Contact: Camille Saurel

Influence of diet assemblage on Ostrea edulis larval development (special course)

The food quality is essential for a successful production of oysters and various monocultures and mixtures of microalgae, to obtain the right composition, have been used. In the oyster hatchery at the Danish Shellfish Centre 4 species of microalgae are currently cultures and fed in a mixture to the oyster larvae. The current project aim on selecting the ideal diet for O. edulis larvae to optimize growth, survival and development. The aim of the project is to study the effect of algae concentration and species on the development of oyster larvae (O. edulis). The growth, survival and development of the larvae will be studied in controlled laboratory experiments. Larvae from the same spawn will be fed cultured algae in mixed diets in different concentrations to see when optimal growth is obtained and evaluate development, settling and survival rate. A known number of larvae will be added to the containers with controlled concentrations and proportions of microalgae, including the mixture currently used in the production, and then followed every day by taken subsamples to measure and count the larvae. The period the larvae are free swimming is 15-20 days. A part of the project will also be learning how to culture microalgae and oysters on a larger scale and you will be a part of the oyster hatchery team. Duration: 2 months (10 ECTS) between end of April – beginning of June 2016.

Control of toxic micro algae in aquaculture systems (bachelor or master)

Growth and accumulation of micro algae is a great challenge in recirculating aquaculture systems. Conditions in both fresh and saltwater system might favor algae growth and there is an urgent need to control growth of micro algae to protect the fish.  Investigations including selected easy degradable algaecides and different algae cultures will provide new knowledge on water treatment potential. The experiments can be performed in Hirtshals.

Contact: Lars-Flemming Pedersen

Automatic low-dose H2O2 addition to aquaculture systems (bachelor or master) 

Prolonged low dose of hydrogen peroxide is considered an option to improve water quality in aquaculture systems and to control microbial water quality. It has only been systematically tested for less than 24 hours and requires additional documentation over several days. An automated H2O2 online sensor with dosage control has been made and experiments will include test in pilot scale recirculating systems at the research facilities in Hirtshals.

Contact: Lars-Flemming Pedersen

Test and development of protein skimmer/foam fractionators (bachelor or master)  

One way to further improve water quality in recirculating aquaculture systems is by using a protein skimmer. Based on pilot scale studies, effects of protein skimmers on different water quality parameters can be evaluated. Among others, removal efficiency of organic matter and microalgae would provide information of interest to improve and dimension protein skimmers. Experiments will be made at the aquaculture facilities in Hirtshals.

Contact: Lars-Flemming Pedersen

Test and implementation of visual water quality measure with KMnO4 (bachelor or master)

Different water quality composition and system design complicates guideline for water treatment and sanitation purposes. The purple oxidant KMnO4 can be used as a visible indicator (contrast agent) of water quality, system hydraulics and disinfection demand. The development of a method on how to apply the chemical and interpret the changes in color intensity will be very useful for optimizing management and hence be implemented by the industry. Studies will be made in Hirtshals and eventually on commercial fish farms.

Contact: Lars-Flemming Pedersen

Study on fish behavior and exposure to water disinfectants (bachelor or master)  

When sanitizers and disinfectants are added to the water in the rearing units, fish usually react transiently by changing behavior. Is has been observed that the patterns of response ceases over time and repeated application of a specific chemical also have less effects. The topic for further investigation is to compare stress response and recovery according to chemicals, dose-exposure and temperature. Studies will be made in Hirtshals.

Contact: Lars-Flemming Pedersen

Test of chemical degradation in aquaculture constructed wetlands (bachelor or master)

There is presently limited knowledge on the removal of chemicals in aquaculture effluents. In particular, new investigations should compare removal capacity in new and mature constructed wetlands associated with commercial trout fish farms. The chemicals of interest are hydrogen peroxide, peracetic acid and formaldehyde – all used to improve water quality in the rearing facilities. Investigations will be made as field measurements where logging, flow measurements and time-series water samples will be collected; chemical analysis will take place in the lab.

Contact: Lars-Flemming Pedersen

Efficiency of aeration and degassing installations in recirculating aquaculture systems (master)

In the production of fishes in recirculating aquaculture systems oxygen is consumed from the water from respiration of fish and bacteria, as well as from the degradation of organic material. The result is a decrease in the oxygen content of the water which must be replenished, and an equimolar increase in carbon dioxide which must be removed. The most common way of achieving this is by the delivery of air at depth through fine diffusors. This approach was developed several decades ago, and has the advantage that it is a fairly simple installation less prone to mechanical failure and that it can also serve to move water and create circulation. The disadvantage is that it is not particularly efficient at aerating water, it has a risk of generating supersaturated conditions with nitrogen gas, and that it also generates turbulence which is costly for fish to swim in. The purpose of this project is to establish an overview of the mechanical and economical efficiencies of different aeration and degassing methods, through literature studies and practical experiments in order to provide a recommendation for suitable aeration and degassing methods for present day aquaculture purposes, while considering the need to circulate water. The project can be carried out in collaboration with the pump industry.

Contact: Peter V. Skov

Respiration of fish tissues; dependency of tissue lipid composition (master)

Highly unsaturated fatty acids (HUFAs) are essential in the diet of carnivorous fishes such as rainbow trout. Rate of uptake and metabolism can be manipulated through changes in exercise regime and dietary content. In mammals and terrestrial ectotherms, the HUFA content in the cellular membranes determines increases the resting metabolic rate due to an increase in membrane fluidity, while in fish the opposite appears to be the case. The purpose of this project is to determine how tissue lipid composition affect the metabolism of fish tissues and the underlying mechanism that are responsible. The experiments should enable the student to set up a mass balance for the energy expenditure in fish with different fatty acid profiles, including retention and oxidation of macronutrient intake under different rearing conditions or dietary regimes.

Contact: Peter V. Skov

Swimming as a tool to manipulate feed intake and growth hormone levels in trout (master)

Exercise in fish is known to manipulate a number of physiological functions. It has been shown that exercise increases the growth rate of salmonids fishes, and it has been hypothesized that this is due to energetic advantages of swimming. We have recently shown that this is not the case; that in fact is much more costly to be reared in moving water (i.e. be forced to swim) that it is to be reared in still water. The explanatory mechanisms for increased growth must therefore lie elsewhere. The purpose of the project is to determine how swimming influences for example macro nutrient utilization, appetite, feed conversion, etc. The project can be performed in collaboration with the feed industry.

Contact: Peter V. Skov