Aquatic & Fisheries GPS Fish Tracking Case Studies Star-Oddi.com

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Star-Oddi and Simrad GPS system (GPS Fish Tracking System)

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Research objectives
Accessibility (Harden-Jones, F. R. Fish Migration (Arnold, London, 1968))
Definition: How accessible are fish for fishery tools, in other words variation of differences in catch effort. Of those fish that are available within the area, a portion come within the influence of the gear and are more or less accessible to capture.

When and for how long do the fish stay in the area?
Measure if the cod are far from the bottom (acting pelagic) and are thereby not accessible for bottom trawl.
Are fish on bottoms that cannot be fished with bottom trawl, but are accessible for net and line? With Star-Oddi tags, we are able to estimate, by analysis of data, when it is more likely for the fish to be at the bottom or to be pelagic.
Analysis of fish behaviour in depth gives information on accessibility for different fishing gear.
Vertical distribution, individuals, general trends and stock depth distributions in relation to time (or position).
Ideal for GPS Fish Tracking

Analysing environmental conditions

The analysis of environmental conditions on migration routes (GPS Fish Tracking), and in spawning and feeding grounds can easily be done by using stored temperature and depth measurements.

Analysing growth rate of fish

Growth rate can be estimated by comparing fish weight and length between times of tagging and recapture. By correlating the growth rate with the stored information on the ambient temperature fish were exposed to, researchers have information on modelling growth rate in relation to environmental temperature.

Availability (Harden-Jones, F. R. Fish Migration (Arnold, London, 1968))
Definition: How much of the stock is in the area where fishery or sample fishing is performed.

Migration of large quantities from one area to another.
Seasonal migration e.g. wintering areas and spawning grounds.
Tags give geographical positions where the fish are, which is an obvious advantage for analysing availability. Give information on migration mechanism and fish behaviour at given positions, offers numerous possibilities for analysis by researchers and institutes.

Detection of commercially harvested fish/stocks

Simrad sonars are installed on a large portion of the fishing fleet. Having fishing vessels transmit GPS signals through the on-board sonar, coverage of areas can be increased considerably, transmitting positions of commercially available species as well as other fish.

Easy to use on vessels

It is possible for researchers, for limited cost, to have vessels transmitting continuous GPS signals by installing GPS transmitters on vessels that are sailing same/similar routes regularly. This could be done on lakes, rivers, in channels or oceans. To obtain complete coverage researchers could use other types of vessels to cover other areas of interest.

Fish behaviour

Position, temperature and depth information give access to valuable information on individual fish behaviour.

Ideal for modelling

GPS position information on fish opens new dimensions for researchers in modelling, allowing them to use GPS information together with environmental information from the tagged fish, such as temperature and depth. Modelling could be used to give managers and researchers new information for making case studies, on predicting future behaviour/reaction of fish in relation to change in environmental conditions, or even behaviour of stocks.

Migration, distribution and mechanisms

GPS tags give researchers improved knowledge on migration routes of commercially exploded fish, information that will improve stock estimates and strengthen the decision process for quotas, contributing to sustainable resource management of fish stocks.
Improved knowledge on fish migration routes will improve our understanding of mechanism that lie behind orientation and navigation of marine animals, one of nature?s mysteries.
GPS positions of fish give valuable information on fish migration and distribution. When the GPS sonar is out of range of the tagged fish, the tag still measures and stores temperature and depth information, giving the researcher information on behaviour between positions.
The measurements give general trends in the depth distribution of individual fish, information that could be used to determine the behaviour of stocks.
GPS tags give researchers information used in analysing what influences migration, and shoals behaviour, vertically and/or horizontally.

Positioning salmon and anadromous trout and charr

It is possible, by scanning coastlines to transmit positions of fish and to analyse coastal migration.
Conduct escape tests from fish cages to analyse migration, behaviour, and possible mixing with other fish.

Resource Management

Fish position gives researchers information that can be used to analyse migration routes, and to identify spawning and feeding routes. The information can be used by ecosystem-based management in selected areas and/or fish stocks with the objective of obtaining sustainable fisheries.

Vulnerability (Harden-Jones, F. R. Fish Migration (Arnold, London, 1968))
Definition: Vulnerability, related to catchability is the integration of fish and the amount caught with gear which is both available and accessible.

How large a portion of the fish that is within the range of a tow area is caught
It is difficult to analyse fish response to fishing gear and the efficiency of different fishing gear with DST alone. In such cases, one would be able to follow individual fish and their response to the fishing gear
Temperature influence on vulnerability / catchability of fish with different fishing gear