Common Stingray - Biology and Ecology

Biology and Ecology

Encountered singly or in "social" groups, the common stingray appears to segregate by sex to some degree and may be more active at night, tending to bury itself in sediment during daytime. It feeds on a wide variety of bottom-dwelling organisms, including crustaceans, cephalopods, bivalves, polychaete worms, and small bony fishes. It is reportedly does great damage to cultured shellfish beds. One study in the Gulf of İskenderun off Turkey found that crustaceans comprised some 99% of its diet, with fish prey becoming increasingly important with age. Another study off the coast of Cilicia, Turkey, found the most important dietary component to be the penaeid shrimp Metapenaeus stebbingi, followed by the pistol shrimp Alpheus glaber and the swimming crab Charybdis longicollis; cephalopods were relatively important for males, while fishes were important for females. Common stingrays have been observed closely following each other in the presence of food, possibly to take advantage of other individuals' foraging success.

Like other stingrays, the common stingray is aplacental viviparous: the embryos are initially sustained by yolk, which is later supplemented by histotroph ("uterine milk", enriched with proteins, fat, and mucus) delivered by the mother through numerous extensions of the uterine epithelium called trophonemata. Females bear two litters of 4–9 pups per year in shallow inshore waters, following a gestation period of four months. Various authors have generally reported birthing in summer, between May and September or over a narrower timeframe such as July to August. Mature rays are known to aggregate off the Balearic Islands from mid-June to July, possibly for reproductive purposes. Newborns measure about 8 cm (3.1 in) across and 20 cm (7.9 in) long. Males reach sexual maturity at 22–32 cm (8.7–13 in) across, and females at 24–38 cm (9.4–15 in) across. The oldest known individual from the wild was ten years of age, but the species has lived up to 21 years in captivity. Known parasites of the common stingray include the flukes Heterocotyle pastinacae and Entobdella diadema, and the tapeworm Scalithrium minimum.