What we do and how we approach it

WHAT WE DO AND HOW WE APPROACH IT

Below you will find a description of our main areas of research and of the rationale and approach that we take.
A list of current and planned research projects can be viewed HERE.

Sensory Biology and Behaviour in Support of Marine Ecology, Fisheries Ecology, and Aquaculture

In order to design an adequate rearing environment for marine organisms, we must first know details of their fundamental biology and ecology: their sensory abilities (particularly vision and olfaction, since their feeding behaviour is guided primarily by these two senses), their behaviour under different rearing conditions, and also how both of these change with size and developmental state. Until recently, this kind of information was extremely difficult (sometimes impossible) to obtain, and it was always time-consuming to generate.

The kinds of questions which we must ask, and answer, before attempting to develop husbandry protocols for a marine species are, for example:

– What can these organisms see (light intensity and quality, imaging of prey and feed particles, etc.) at different life stages? This knowledge can be used to optimize the lighting conditions under which they are raised. Even small changes in light intensity and quality can have significant effects on the feeding behaviour and, therefore, survivorship and growth, of marine organisms. Despite this, the choice of light environment for rearing has, with few exceptions, been little more than guesswork.

– What can these organisms smell at different life stages and do they “prefer” some odours (e.g. exudates of specific prey) over others? Can such odours be used to enhance feeding rates? Very little is known about the olfactory abilities of marine organisms, nor of its role in feeding. In fact, only a handful of such studies exist for fishes, and that work has been mostly on salmonids, which do not have a true larval period.

– What roles do container size and colour, and water movement, temperature, salinity etc., play in feeding behaviour? Although these issues have been examined separately, their interaction has not been rigorously investigated.

– What prey characteristics (e.g. size, colour, movement pattern, odour, consistency) determine food preferences of marine organisms at different life stages?

These are only a small subset of the questions that remain to be addressed. To increase the probability of successfully developing a species for commercial production, we must be able to systematically address these types of questions, from first principles.

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A unique approach to answering these questions

The first principles approach requires an ability to collect information on the fundamental biology and life support requirements of organisms targeted for aquaculture. Our approach brings together several modern biomedical and ethological techniques in order to generate the kinds of information that are essential to the planning and implementation of husbandry protocols for marine organisms targeted for commercial production.

The basis for the utility of these techniques is that they all allow the researcher to ask questions of organisms which cannot communicate with us verbally.

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Techniques to study vision: spectroradiometry and microspectrophotometry

Spectroradiometry is used to measure light (intensity and quality), in the air and underwater. We use a high-resolution portable scanning spectroradiometer to measure the light field in natural environments, sea pens, indoor aquaculture systems, and experimental settings. The instrument can also be used to measure spectral transmission through materials and/or organisms, and reflectance off surfaces. In this way, we determine what intensity and quality of light to mimic in experiments and in rearing environments.

Microspectrophotometry (MSP) is a refinement of spectrophotometry. A finely-focussed beam of light is directed through the outer segment of photoreceptor cells (the cells upon which vision is based) and absorption profiles of the photopigments contained therein are generated. In this way, we can ask marine organisms what colours of light they can see. This information allows us to match the light environment in a rearing system to the characteristics of the organism’s visual system, and to make appropriate adjustments as they grow.

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Technique to study vision, olfaction and mechanoreception: electrophysiology

Electrophysiological recordings allow investigators to determine the physiological responses of animals to their surroundings and the manner in which sensory information is gathered and coded by the central nervous system. Essentially, the technique allows us to ask organisms what they see, smell, hear and feel (i.e., the tactile sense). Thus, this approach is used to evaluate sensory responses to various stimuli (such as those that would be present under different rearing conditions) and also how these responses change with age, developmental state, stress, nutritional condition, endocrine status, reproductive maturity, etc. Although applied mainly to larger animals, it is now possible to make such measurements on larvae.

This technique enables us to address, by direct measurement, such fundamentally important issues as the olfactory and mechanosensory responses to sets of stimuli that are present in alternative rearing systems. As with the MSP technique for the visual environment, such information allows us to evaluate how we might improve rearing conditions by considering the compounding effects of olfactory, mechanosensory and visual stimuli. In addition to generating information of direct relevance to aquaculture, these techniques allow us to address more fundamental questions related to the development of information processing in fishes and how this might be affected by the environment at different points in the life history (for example, during “critical periods”). Such an analysis at the electrophysiological level can then be compared to results from analogous studies at the morphological and behavioural levels.

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Techniques to study behaviour: silhouette and schlieren imaging and motion analysis

Silhouette video-based (SVP) three dimensional motion tracking and move path analysis allows detailed observations of the reactions of aquatic organisms to different environmental conditions. SVP is superior to standard cinematographic or video imaging techniques in various ways. First, it allows filming of events in a large depth of field (approximately 20 cm) with a relatively large field of view (15 cm). Second, magnification is independent of distance from the cameras and the resolution is very good; objects as small as 0.2 mm can be resolved. Third, image quality is unaffected by ambient light levels and the silhouette effect is attained without the use of intense light sources. As such, the behaviour of fish larvae and zooplankton can be observed under relatively natural conditions.

Schlieren video-based three dimensional analysis allows for more detailed/finer spatial scale observations than does SVP. Using 3 expanded and collimated HeNe lasers, we can observe the 3 dimensional coordinates of all particles larger than 3 um within a volume of 45 ml. Magnification is easily adjusted to provide a pixel resolution ranging from 1.5 um/pixel to 55 um/pixel. The light source and cameras are aligned to record from 3 perpendicular angles simultaneously. This redundancy ensures that the 3 dimensional location of any object ca not be shadowed by another object.

Analysis of the images obtained from these optical systems allows for detailed characterization of the reactions of aquatic organisms to different environmental conditions. These data provide information on the overall activity, swimming patterns, prey search behaviour, foraging and feeding rate, prey selectivity, attack success, etc. All of these variables are directly relevant, and of great importance, in developing appropriate rearing environments for intensive aquaculture and for parameterizing the predator-prey components of ecosystem models. Such observations can also be used to evaluate different combinations of rearing conditions and/or environmental conditions (e.g. in the context of global climate change).

For more information, see Browman, H.I., J.-F. St-Pierre, A.B. Skiftesvik & R.G. Racca. 2003. Behaviour of Atlantic cod (Gadus morhua) larvae: an attempt to link maternal condition with larval quality. pp: 71-95, In: H.I. Browman and A.B. Skiftesvik (Editors). The Big Fish Bang. Proceedings of the 26th Annual Larval Fish Conference.

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The information on this page was last updated on 1 December 2010.