Size at maturity in the mud spiny lobster Panulirus polyphagus (Herbst, 1793)

The size at sexual maturity of the mud spiny lobster Panulirus polyphagus was estimated by assessing the sizes at which the animals become morphologically, physiologically and functionally mature, from samples collected from the wild along the Saurashtra coast. The size at physiological maturity was assessed from the condition of the gonad and its stage of development. The size at morphological maturity was assessed by following the development of external indices of maturity. Change in the length of the penile process in relation to the carapace length (CL) was also studied in males. Linear plots of the somatic lengths against the carapace lengths in size groups 50 mm CL were used to assess changes in growth patterns from juvenile phase to sub-adult and adult phases. Comparisons were also made between growth patterns of males and females. The size at functional or physical maturity was assessed from the frequency distribution of males and females with respect to specialised structures which ensure the mating and propagative capabilities of the animals, namely, decalcified windows on the ventral side, well developed setal brush on the dactylii of the fifth pair of walking legs and ovigerous condition in females and penile process in males. Observations made in the study indicated that the size at onset of sexual maturity can be traced to 51–55 mm CL for males and 51–60 mm CL for females. The critical maturation phase extends between 56 and 65 mm CL for males and between 66 and 75 mm CL for females