Relationship between repaired shell damage and fishing disturbance in the Patagonian scallop Zygochlamys patagonica.

BETINA JUDITH LOMOVASKY; MARIO LASTA,; SILVANA CAMPODÓNICO; OSCAR IRIBARNE,

Mooloolaba, Queensland, Australia

Congreso; 15th International Pectinid Workshop; 2005

Under reflecting light, acetate peels from the polished shell cuts of Z. patagonica showed a pattern of alternating broad opaque and narrow translucent growth bands. Repaired shell damages were observed in some individuals in different parts of the valve. In general, during the process of shell repair, sediment particles were trapped in the damaged area between the old and newly accreting shell. The photomicrographs of acetate peels showed alterations in the growth band deposit, and sediment grains into the shell matrix between two growth bands. The frequency of repaired shell damage in scallops from different beds analyzed in this study showed a higher percentage in TangoB bed (32%), than Uruguay and Reclutas (12%), with the lower value in Beagle bed (9%). The commercial fishery intensity in the 4 beds showed the higher intensity in TangoB, next Reclutas (with only a minor research disturbance in the area) and Uruguay bed (negligible disturbance) with null fishing intensity (no disturbance) in the Beagle bed. The frequency of damaged scallop observed in those beds-areas not targeted by the fishery (Uruguay, EFA in Reclutas and Beagle bed), assuming not anthropogenic disturbance by fishing, could be related to all natural causes of disturbances that produce injury to be repaired (i.e., predation). The difference between the 32% of scallop damaged in Tango B with values on none (or negligible) disturbed beds could be attributed to the fishery impact or disturbance in the bottom. If we consider that scallops make a major energetic investment in repairing their shells, which is likely to affect their growth rate at the expense of adductor muscles mass, the fishery may be having some non-lethal effects on the Patagonian scallop populations. Given the importance in some beds, this potential effect needs to be studied.