Size distribution, length–weight relationship and size at the onset of sexual maturity of the orange mud crab, Scylla olivacea, in Malaysian waters

ABSTRACT

The size distribution, length–weight relationship and size at the onset of sexual maturity of the orange mud crab (Scylla olivacea) from four geographically distinct locations (Taiping, Setiu, Kota Marudu and Lundu) representing Malaysian waters were analysed and estimated. Scylla olivacea was found in the size range of 47–134 mm carapace width. Males were significantly smaller in size but heavier than females. Geographical variation in carapace width and body weight were significant, but no interaction was found between sexes and locations. As shown by the length–weight relationships of S. olivacea, the males exhibited positive growth allometry whereas the females exhibited negative growth allometry. Males mature physiologically prior to attaining morphometric sexual maturity. Females, however, achieve physiological and morphometric sexual maturity in synchrony. No significant variation was found in the estimates of size at the onset of sexual maturity of males and females among different locations. We recommend the use of the third right walking leg merus length and carapace width to estimate the size at the onset of sexual maturity (morphometric maturity) for S. olivacea. Data obtained in this study serve as important baseline data for future mud crab resource management in Malaysia and were used to recommend minimum landing sizes for S. olivacea in each respective location based on the largest size at the onset of sexual maturity estimates were suggested.

RESPONSIBLE EDITOR:

• Roy Kropp

KEYWORDS:

• Size distribution
• length–weight relationship
• allometry
• size at maturity
• Scylla olivacea; orange mud crab

Acknowledgements

We gratefully acknowledge the Institute of Tropical Aquaculture, Universiti Malaysia Terengganu, Malaysia for providing measuring equipment during sampling. We thank Wan Ibrahim Wan Nurfaizza and Fadhlul Hazmi Megat for their assistance in sample collection. This manuscript was greatly improved by the helpful suggestions of Dr Roy Kropp (Pacific Northwest National Laboratory) and three anonymous reviewers. Sincere gratitude is extended to Daniel Paul Langston for his proofreading of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Malaysia’s Ministry of Higher Education under the Prototype Research Grant Scheme (PRGS) [grant no. 54243] and the Niche Research Grant Scheme (NRGS) [grant no. 53131].