Reproductive potential of the lithodids Lithodes santolla and Paralomis granulosa (Anomura, Decapoda) in the Beagle Channel, Argentina

Lithodidae is the only group of reptant decapods that occurs in Antarctic waters and has been particularly abundant in the Beagle Channel, Straits of Magellan and south to 50 degrees S. Because of their abundance in coastal waters, the sympatric Lithodes santolla and Paralomis granulosa have constituted a mixed fishery since the 1930s. The two species differ markedly in their reproductive potential. Lithodes santolla is large (maximum size of 190 mm carapace length, CL, and 8 kg weight), has a generation time of 6 yrs., the reproductive cycle is annual and females carry between 5,000-60,000 eggs per female per clutch. In their life span, L. santolla females produce 6 times more eggs than P. granulosa females. Paralomis granulosa is smaller than its relative (maximum 115 mm CL and 1.5 kg weight), and has a slower growth rate, resulting in a generation time of 12 yrs. The reproductive cycle is biennial and females carry between 800-10,000 eggs per female per clutch. Moreover, the reproductive potential of P. granulosa is reduced because an important proportion of the largest and more prolific females of the population do not carry eggs. In other terms, in one generation time of P. granulosa, two complete generations of L. santolla are produced, and compared to other Subantarctic lithodids L. santolla is the most prolific species. The higher reproductive potential of L. santolla probably confers to this species the ability to recover more rapidly from an overfishing situation.