Abstract
The reproductive cycle of Acanthocardia tuberculata (Linnaeus, 1758) was studied in M’diq Bay. The gonadal development was determined by means of standard histological techniques, mean oocyte diameters and a condition index. Rough cockle is a gonochoric species with synchronous gonadal development and spawning in males and females. The sex ratio obtained was not significantly different to 1:1. Gametogenesis began in late winter (November) coinciding with the temperature drop. In June, with increasing sea water temperature, most of the population was spent and resting oocytes appeared dispersed in the gonad. Resting stage occurred from August to October, during which time sex could not be determined in 100% of the population. A. tuberculata showed a clear seasonality in its gametogenic cycle, with one spawning peak per year in June. Quantitative measurements of 6318 oocyte diameters indicated the patterns of development observed in the qualitative staging. The results obtained revealed the direct influence of temperature on the reproductive cycle. First sexual maturity occurred at 42.77 mm shell length. The information gathered in this study allowed preliminary management measures to be suggested for the fishery of this species, including a closed season during the main spawning season (May-June) and the establishment of a minimum landing size (at least 50 mm shell length) for A. tuberculata from the Moroccan Mediterranean coast.
Highlights
The cockle Acanthocardia tuberculata (Linnaeus, 1758) is an Atlantic-Mediterranean species whose habitat ranges in the Atlantic from the southwestern British Isles to Morocco
The gonadal development was determined by means of standard histological techniques, mean oocyte diameters and a condition index
Resting stage occurred from August to October, during which time sex could not be determined in 100% of the population
Summary
The cockle Acanthocardia tuberculata (Linnaeus, 1758) is an Atlantic-Mediterranean species whose habitat ranges in the Atlantic from the southwestern British Isles to Morocco. In Morocco A. tuberculata mainly occupies the depth ranged between isobaths 5 and 15 m and currently inhabits the shellsand sediments admixture with gravel to muddy sand (Rharrass et al 2011) This fishery is located of the northwest coast of Morocco, involves more than five hundred fishermen and is very important for the local economy. This species is mainly exploited in this area by a fleet of 107 boats using the manual Portuguese dredge, which has remained unchanged throughout time It consists of a small, heavy semi-circular iron structure with a net bag and a toothed lower bar at the mouth. In the north of Morocco, as at another localities (Spain, Portugal, Croatia, Greece), A. tuberculata is usually caught for human consumption along with the smooth clam (Callista chione) Both species often dominate the benthic macrofauna in M’diq Bay (Rharrass et al 2011). As reported by Peharda et al (2012) among others, in the areas of the Adriatic Sea these bivalves are collected by Scuba diving and A. tuberculata is not harvested for human consumption, though empty shells and occasional live specimens are collected sporadically for decorative purposes
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