Egg production and validation of clutch fullness indices scale of southern king crab, Lithodes santolla, in the Central Patagonian Sector, Argentina (44°–48°S)

Egg production of the southern king crab Lithodes santolla from the Central Patagonian Sector, Argentina was assessed by analyzing the size - fecundity relationships and egg quality of this species. As well, the effect of spatial variability of these parameters was studied. Furthermore, the effectiveness of the "Clutch Fullness Indices" (CFI) scale used for detects variations in egg production of this species was analyzed. Fecundity of L. santolla, during the 2015–2016 season, showed a positive relationship with female size (CL) and ranged between 1780 and 36,788 eggs for females between 64 and 123 mm CL. In the present study, fecundity did not differ among Central Patagonian Sector areas. In addition, visual assignment of CFI was associated with different size-fecundity relationship; females with low CFI scores had lower fecundities. These results suggest that the current CFI method can be used as a tool to understand spatial and temporal variability egg production for L. santolla, in particular may be useful to distinguish large differences in fecundity (e.g., >50%). L. santolla egg diameter values ranged between 1537 and 1984 μm. This variable showed no relationship with the female’s size and did not differ between CFI categories or location. On the other hand, egg dry weight (DW) ranged between 38 and 68 mg (x 50 eggs) and showed a positive relationship with female size. This result suggests that DW may be a more sensitive index to evaluate egg quality for this species. It was observed that eggs of females with 50% CFI also had a significantly lower DW than those corresponding to females with 100% CFI, which would indicate that both the number and the quality of the eggs would be affected in females with lower CFI values. Moreover, differences in egg DW between Central Patagonian Sector areas were found. These results support the "maternal effect" hypothesis in L. santolla, which proposes not only higher fecundity in larger females, but also better quality eggs. These results provide critical data that may be used in stock assessment models to establish a base line to evaluate the effects of fishing and environmental changes on reproductive potential.