Reproduction of Megapitaria squalida (Bivalvia: Veneridae) in the Southeast Gulf of California, Mexico

Abstract

Abstract:Bivalves reproductive cycle varies according to the particular environmental conditions where they are found, and these reproductive details represent basic information for their capture, management and conservation strategies. With this objective, the reproductive cycle of the clam Megapitaria squalida, inhabiting the Southeast of the Gulf of California (Altata Bay, Sinaloa, Mexico), was studied using histology and changes in the number and size of oocytes, from June 2013 to June 2014. Histological analysis of the gonads showed spawning activity throughout the year, with two peaks. The first was registered in October and it was accompanied by the highest decrease of weight; the second was in February with the highest percentage of spawning population; besides, a resting period was observed in December. The sex-ratio (female:male) of the clam population was 1.08:1 (χ 2 = 5.72, d.f. = 1, P < 0.05). Mean oocyte size and number were different (P < 0.05) among all sampling months and fluctuated from 34.6 ± 5.8 µm in June 2014, to 41.9 ± 6.8 µm in February 2014, and from 443.8 ± 424.5 in February 2014, to 1 214.4 ± 267.6 counted in April, respectively. With these results we suggest a protection season from October to November, when the most intense release of gametes occur in this population. Rev. Biol. Trop. 65 (3): 881-889. Epub 2017 September 01.Key words: gonadic index, Megapitaria squalida, oocyte development, spawning season, capture management, conservation.Studies on reproduction of commercial bivalves are essential to come up with management strategies for their conservation and sustainable exploitation. The clam Megapitaria squalida (Sowerby, 1835) commonly known as "squalid callista" or "callista clam", is distributed from the North of California (Scammon's Lagoon) along the Pacific coast, to Mancora, Peru, and in both coasts of the Gulf of California. It is a filter-feeder that lives burrowed in sandy sediments, from intertidal areas to depths of about 160 m (Keen, 1971), and its shell can reach a length, height and width of 120, 97 and 68 mm, respectively (Singh, Vélez, & Fajardo, 1991).Although this species is considered as a resource of low commercial value, it is particularly appreciated in Mexico, and represents an important alternative fishery in the Gulf of California and the Pacific coast of Mexico. Commonly, clams are captured for personal consumption or sold in local and regional markets. M. squalida is harvested by free or scuba diving until a depth of 10 m, and is also hand collected in intertidal sand flats (Scheweers, Wolff, Koch, & SinselDuarte, 2006). There are some reports about its exploitation in Bahia Concepción (CastroOrtíz, Tripp-Quezada, & Anguas-Velez, 1992) and different coastal locations of the Gulf of California, Mexico (Baqueiro-Cárdenas, Masso, & Guajardo, 1982). However, López-Rocha et al. (2010) Latest production statistics in 2014 report a total volume of 4 319 tons of which 99.7 % were registered from Northwest Mexico, and the rest for the state of Sinaloa, in th...