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No By-catch!

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      By-catch is defined as the unwanted species of fish or marine creatures who are caught in a net by fisherman.  Some students ask about what was kept from the nets vs what was thrown back in the water.  On this trip there is no such thing as by-catch.  Everything that is caught will be used and analyzed to help paint the picture of what is going on in the different layers of the ocean. Above is an example of what might come from just 1 net in the trawl (which has 6 nets total).    This varies with depth and whether the trawl was done in the daytime or night.  

       Everything is kept for abundance and diversity measurements. However species are needed for a number of other projects - DNA, stable isotopes, parasites or hydrocarbons..  Before coming on the research trip scientists collaborated and identified the species needed for these projects and these specimens are processed immediately on board the ship after each trawl.   The rest of the animals are stored in formalin and will be analyzed back on land at different university labs.

 Here is a picture of the different tags that are placed in the specimen sample dishes.  Each sample is given a net number, an identification tag with the genus and species name.  The N tag tells what net the specimen came out of.  The processed samples receive a printed label with more specific details including latitude, longitude, date and trawl number.  This makes sure the correct information is stored with each specimen.   This is critical when you are dealing with tens of thousands of specimens.

 Here is a picture of how the scientist begin the identification process and sort organisms into broad groups.






Fish ready to be identified.


Here are some more pictures after the specimens have been sorted and identified.  They are then processed and stored.  


                           Fish sorted and identified.                                                                           Classified crustaceans.

Teacher At Sea,

Christia Hewlett



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  • Guest
    Deanne Edman Wednesday, 11 May 2016

    Hi Mrs Hewlett,

    While in the Gulf of Mexico did you observe any algal blooms?

  • Christia Hewlett
    Christia Hewlett Saturday, 14 May 2016

    Deanne, we did not observe any algal blooms.

  • Guest
    George Wednesday, 11 May 2016

    Hi Mrs.Hewlett what chemicals did you use to process and store the fish in order to preserve them?

  • Christia Hewlett
    Christia Hewlett Saturday, 14 May 2016

    George, we used formalin to store some samples. Other samples were stored in ethanol.

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Guest Wednesday, 19 June 2024