Crustacean

Spider crab
The spider crab (Maja squinado) is a decapod that belongs to the Majidae family. This is a species that lives in the Northeast Atlantic Ocean and Mediterranean Sea, at depths ranging from the sub tidal level to 90 meters. The males of this species can attain a maximum carapace length of 23 cm and a weight of 4.5 kg. The females are smaller, 20 cm in carapace length and weighing 2.8 kg.
 
 

The adults are known to show clear directional movements towards deeper water in late summer and in the autumn. This migration is linked to the weather conditions. The spider crab fishery is highly important in Spain, with a mean value of 122 million tons per year between 1986 to 1990.

In 1996 a few spider crabs were tagged with DST 200 at the Galcian coast in NW Spain by Professor Eduardo González-Gurriarán, and his group, from the University of Coruña, Spain. The DST 200s had both depth and temperature sensors. The crab were also tagged with ultrasonic transmitters in order to establish a relationship between real position and the date from the DST, after the tag had been recovered. Only mature adults were tags in order that the tags would not be lost when the animals were moulding. The animals were tagged in shallow water (<10 m), weighed about 1 kg and were 13 cm in carapace length. The recapture rate was very high (over 70%), mainly due to high fishing effort, tracking and good co-operation between the local fishermen and the research group.

These results have been published in a scientific paper. This paper is also available on this web page:
1998. New approaches to the behavioural ecology of decapod crustaceans using telemetry and electronic tags. Hydrobiologia 371/372: 123-132.