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A basic task with electronic tags is to reconstruct the migration routes of the fish. Scientists from the Danish Institute for Fisheries Research (DIFRES) do this in the Baltic Sea by correlating measurement of salinity and temperature obtained from DST CTD tags with information from a hydrografic model.
According to the scientist from DIFRES the idea behind the method is that there is a strong gradient of salinity in the Baltic, with high salinity at the entrance in the south, and declining salinities up through the estuary.
 This means that by correlating the information of local salinity and temperature from the tag with the hydrographic model, the scientists have been able to reconstruct the horisontal movement of the fish.
The DIFRES report is available on Star-Oddi´s website (www.star-oddi.com) in the "Scientific Papers" section, or click here to open the report "A method to goelocate eastern Baltic cod by using Data Starage Tags (DSTs)" written by Stefan Neunfeldt, Hans-Harald Hinrichsen and Anders Nielsen.
The new DST measures additionally to temperature and depth, relative pitch and roll movements of the DST, with reference to the earth gravity. The measuring parameters are measuring the gravity movements in two directions:
The picture shows the measuring directions of the sensor relative to the DST housing.
The DST pitch and roll tag allows the scientist to take frequent sampling of the orientation of fish using different sampling intervals. Measuring resolution is better than 1°.
The sensor can be used for analysing movements of marine animals as well as various underwater gear. For analysing fish movements, it is advised to fasten the tag at both ends for avoiding / limiting movements of the tag. The tag has a measuring range of approximately +/- 45° in each direction.
Application examples:
- For analysing fish movements/orientation in relation to buoyancy (gas in/out from swimming bladder).
- Analysing fish target strength in acoustic surveys in relation to their behaviour and orientation, for improving biomass estimations.
- Finding pattern in fish behaviour, diurnal/seasonal, for improving acoustic surveys estimation of biomass.
For further information contact Star-Oddi sales and get a price quote.
Product specifications for DST pitch & roll.
A new deep setting technique has been tested for tuna and swordfish longlines, that was designed to avoid shallow water bycatch species and improve catch rates for bigeye tuna.
The objective of the project, which took place during March-May 2004, were to perfect the new deep setting technique so that it could be duplicated by any longline boat, and to test it alongside normal setting practices to see if catch rates changed. To be feasible, the new technique had to eiter improve or not change catch rates for the main target species, bigeye tuna and broadbill swordfish.
DST centi temperature and depth recorders (TDRs) were used on all project baskets and on some normal baskets for comparison. Without the use of TDRs it is difficult to know the actual depth achieved, because of environmental factors. If the new deep setting technique could land all hooks below 100 m and still fish effectively, then it could be a solution for avoiding turtle bycatch, as the surface down to 100 m seems to be the critical depth of most sea turtles.
Click here to read the article about the experiment with tuna and swordfish longlines where the temperature and depth recorders where used (PDF file). The article is available on a pdf. file in the scientific papers section on www.star-oddi.com.
Star-Oddi employs highly competent team of qualified experts in designing and making micro-electronic sensors and related equipment. If our standard products do not fit your requirements, our products can possibly be customized and adjusted to fit your needs.
We at Star-Oddi are open-minded toward new product development and we encourage our customers and prospects to contact us to see if we can meet your requirements. Please contact Star-Oddi with your inquiries or alternatively call (+354) 533 6060.
For the last 12 months Star-Oddi has been able to introduce a new product every third month. This fact shows that Star-Oddi is enthusiastic company trying its best to serve the customers´ needs. We are looking forward introducing number of new innovative products in 2005, broadening the customer base of Star-Oddi, and strengthening the firm profile with the customers.
We encourage you to contact us with your requests.
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