Request to measure clasper length

A request from James Thorburn – As part of my research, I am trying to identify important areas for tope and spurdog, such as breeding grounds and nursery areas. As part of this, it is important to gauge the maturity status of both sexes in the area. With female sharks, other than size, there are not a lot of external signs to estimate maturity but with males, the length of the claspers can be a good indication of maturity.

Tope, claspersIn view of this, I am asking any willing anglers to measure the total length of the fish and the clasper length of any male tope and spurdog. I am especially interested in smaller individuals. This will help identify a maturity size for male tope and spurdog in these areas, helping to show areas and months that are important to the species breeding cycle. The method of measuring is shown below.

Tope claspers

Total length


Clasper length













Clasper measurement is taken from the tip of the clasper to the joining point between the pelvic fins.

You can use the ‘Contact Us’ facility to send any measurements to us and we’ll forward them on to James.

Category: Other Organisations

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