Feed Distribution in Large Scale Sea Cage Aquaculture: Experiments, modelling and simulation

The objective of this thesis was to gain new insight into the process of feeding in large scale sea cage aquaculture and investigate novel methods of feeding in order to increase profitability, welfare and minimize environmental impact. Compared to livestock farming, Atlantic salmon (Salmo salar ) farming is a young industry which has experienced an almost exponential growth rate and the product continues to be in high demand. A single cage in Norway may contain more than a 1000 tonnes of fish in the form of 200.000 individuals. Such a figure is difficult to comprehend, but one may draw a parallel to the equivalent of 1600 cows inside a single cage. Feeding of fish kept in sea cages is a complicated endeavour compared to land based farming for a number of reasons. Thousands of individuals co-exist in a single three-dimensional dynamic space, observation is restricted to surface inspections or a submerged camera with limited field of view, feed can not be given to a specific fish and the location of feed is difficult to predict as a consequence of currents and fish induced turbulence. In addition, feed which is not consumed from the time it is distributed over the surface to it passes through the cage represents a direct economic loss and acts as an unnecessary nutrient discharge to the environment. Over 10.000 kg of feed may be administered to a single cage towards the end of a production cycle and is the single largest cost in Norwegian salmon farming. Even though the process of feeding is a complicated one, the systems used to distribute feed are simple. Significant effort has been made in determining the ration size, meal frequency and at what time of day Atlantic salmon should be fed. This thesis looks into the temporal feed availability on a meal to meal basis and goes into depth with respect to the spatial availability of feed within the sea cage. Many studies on a smaller scale indicate that spatially and temporally restrictive feeding may lead to unequal feed accessibility, loss of growth potential and elevated levels of aggression. With respect to controlling the spatial distribution of feed, it has been shown that current methods cover a small area of the cage surface. In addition, existing methods have limited ability to increase the feed distribution without exhibiting other detrimental effects such as increased pellet breakage. There is also no way of controlling where feed is placed as a consequence of wind or currents. Experimental results are presented to better understand the dynamics of a feed spreader, a model has been developed and the performance of different spreader designs investigated. Further experimental results for settling rate and diffusion of pellets are presented and have been used to parametrize a full sea cage model. This model enables simulation of environmental factors, feeding methods and fish to predict the effect on central production parameters. Finally, using these two models, different feeding regimes are simulated and the consequent effects on spatiotemporal feed distribution, feed intake and feed loss are commented upon. It is likely that by increased use of environmental measurements run through feed distribution models and having more adaptable methods of feed placement, one can in the future minimize the environmental impact whilst maintaining high growth rates and good fish welfare

A Modular Software and Hardware Framework with Application to Unmanned Autonomous Systems: Interacting Modules, Error Detection and Hardware Design

The Department of Engineering Cybernetics at the Norwegian University of Science andTechnology established the Unmanned Vehicle Laboratory fall 2010. The goal is to havestudents develop a fully functional autonomous aerial vehicle over time as part of projects and master s theses. A range of projects were carried out fall 2010, among others the report General Platform for Unmanned Autonomous Systems was written on the topic of hardware, operating systems and peripheral interfacing.This master s thesis continues where the previous report left suggestions for further work, and covers the topics of a software framework, sensor error detection, actuator and sensor interfacing, that is now part of the autonomous flight system.A highly modular software framework has been constructed, applicable far beyond theunmanned vehicle domain. Due to the high level of encapsulation and modularity it isespecially valuable in projects where there is a high mobility of the workforce, such as student projects and theses. It acts as a middleware layer, with language independent, separately compilable modules, communicating with one another to achieve the desired functionality.To prevent unrealistic or erroneous sensor readings from spreading through the system, a software detection unit catches signal anomalies based on statistics and alerts subscribing modules. The algorithm has been interfaced into the software framework, and is applicable to numerous sensors.Hardware was designed, constructed and tested to handle sensor interfacing, power supply demands and real-time critical actions such as actuator control. The design is performed from an aerial vehicle application point of view, but general to such an extent that is usable in a wide range of autonomous crafts.The framework, filter and hardware are merged together and tested on an embedded system, verifying the system functionality with a feedback loop from measurements to actuators. Utilizing the previous work along with all three elements of this thesis, a fully functional system for vehicle control is achieved

Feed intake in Atlantic salmon fed with or without surface spreading of feed

publishedVersio

Feed intake in Atlantic salmon fed with or without surface spreading of feed

In intensive salmon farming, it is common practice to spread the feed over a large surface area, assuming that spreading of the feed increases feed intake in the fish. However, the impact on the feed pellets during spreading results in feed loss due to pellet breakage. In this study, feed intake, growth and signs of aggressive behavior was compared in salmon fed without or with spreading of the feed on the surface area of the tanks. Atlantic salmon (Salmo salar) with initial body weight 0.6 kg were kept in 3.3 m 3 tanks supplied with sea water (salinity 32 %, mean temperature 11 °C) for one month. The salmon were fed one meal daily, either by dropping the feed from one point, or by spreading the feed over the water surface. Feed intake and growth was measured. Fin damage was given a score at termination of the trial as a measure of competitive behavior during feeding. The relative feed intake (i.e. percent of body weight per day) in salmon fed without spreading or with spreading of the feed was 0.63±0.05 and 0.64±0.02 %, respectively. The growth rate was identical in salmon fed without or with spreading of the feed, and no significant difference in variance in final weight was found. No difference in fin damage for salmon fed without or with spreading of the feed was revealed. The data showed that for the conditions used in this trial, spreading of feed had no influence on feed intake or growth of salmon.publishedVersio

Determining spatial feed distribution in sea cage aquaculture using an aerial camera platform

Within this paper we describe an unmanned aerial vehicle (UAV) based method to estimate the spatial feed pellet distribution in salmon fish-cages and exploit it within a case study to determine the radial pellet distribution for different rotor spreaders and blower configurations. Compared to previously used methods, capturing pellets thrown from a rotary feed spreader in rows of Styrofoam boxes, the UAV based method is simpler and faster to setup and allows to cover a larger portion of the sea cage surface area. We compare results obtained with the Styrofoam box method with results we obtained by an automatic analysis of aerial videos taken by the UAV during feeding experiments. The employed method helps to gain insight into the spatial feed pellet distribution in full-scale salmon fish-cages where the feeding pipe and actual fixation of the spreader may influence the dynamic behaviour of the feeding system. This can also be seen as a step towards a continuous measuring of the feed pellet distribution, particularly in view of possible future feeding systems that may allow to adapt the feed pellet distribution to the actual fish distribution

Feed intake in Atlantic salmon fed with or without surface spreading of feed

In intensive salmon farming, it is common practice to spread the feed over a large surface area, assuming that spreading of the feed increases feed intake in the fish. However, the impact on the feed pellets during spreading results in feed loss due to pellet breakage. In this study, feed intake, growth and signs of aggressive behavior was compared in salmon fed without or with spreading of the feed on the surface area of the tanks. Atlantic salmon (Salmo salar) with initial body weight 0.6 kg were kept in 3.3 m 3 tanks supplied with sea water (salinity 32 %, mean temperature 11 °C) for one month. The salmon were fed one meal daily, either by dropping the feed from one point, or by spreading the feed over the water surface. Feed intake and growth was measured. Fin damage was given a score at termination of the trial as a measure of competitive behavior during feeding. The relative feed intake (i.e. percent of body weight per day) in salmon fed without spreading or with spreading of the feed was 0.63±0.05 and 0.64±0.02 %, respectively. The growth rate was identical in salmon fed without or with spreading of the feed, and no significant difference in variance in final weight was found. No difference in fin damage for salmon fed without or with spreading of the feed was revealed. The data showed that for the conditions used in this trial, spreading of feed had no influence on feed intake or growth of salmon

Feed intake in Atlantic salmon fed with or without surface spreading of feed

In intensive salmon farming, it is common practice to spread the feed over a large surface area, assuming that spreading of the feed increases feed intake in the fish. However, the impact on the feed pellets during spreading results in feed loss due to pellet breakage. In this study, feed intake, growth and signs of aggressive behavior was compared in salmon fed without or with spreading of the feed on the surface area of the tanks. Atlantic salmon (Salmo salar) with initial body weight 0.6 kg were kept in 3.3 m 3 tanks supplied with sea water (salinity 32 %, mean temperature 11 °C) for one month. The salmon were fed one meal daily, either by dropping the feed from one point, or by spreading the feed over the water surface. Feed intake and growth was measured. Fin damage was given a score at termination of the trial as a measure of competitive behavior during feeding. The relative feed intake (i.e. percent of body weight per day) in salmon fed without spreading or with spreading of the feed was 0.63±0.05 and 0.64±0.02 %, respectively. The growth rate was identical in salmon fed without or with spreading of the feed, and no significant difference in variance in final weight was found. No difference in fin damage for salmon fed without or with spreading of the feed was revealed. The data showed that for the conditions used in this trial, spreading of feed had no influence on feed intake or growth of salmon