Wise, L. Study on the colonization of traps lost at sea

A study of the colonisation of lost fishing traps was carried out between August 1999 and January 2002. The lost traps and the species colonising them were analysed qualitatively from samples taken over 28 months. The samples were collected by scuba diving and gillnets. The development of the macrozoobenthic community was studied by analysing the relation between the total number of species, the percentage of clogging, the mobility of species, their trophic groups and length of immersion. Colonisation was also studied by determining the number of new species that recurred or were eliminated during the period of sampling. Biometric measurements of two of the colonising species, Chlamys varia (Linné, 1758) and Balanus cf improvisus Darwin, 1854 were used to date the traps. Age determination of the bivalve was not possible due to insufficient number of individuals and lack of knowledge of the periodical deposition of rings in this species. Average maximum operculum diameter, average maximum base diameter and average maximum height of Balanus cf improvisus were measured to determine the respective allometric relationships. Colonisation was slow but similar to others occurring in hard artificial substratum. Of the 62 species observed, the majority were Arthropods, Molluscs and Annelids. The dominant species was the barnacle Balanus cf improvisus. Although a strong relation between the maximum operculum diameter and the length of immersion was found, this approach did not prove efficient in determining the age of lost traps. A true ecological succession besides the initial state was not found.