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. 2023 Aug 21:11:e15849.
doi: 10.7717/peerj.15849. eCollection 2023.

Feeding ecology and reproductive biology of small coastal sharks in Malaysian waters

Kean Chong Lim  1   2 , Amy Yee-Hui Then  1   3 , Kar-Hoe Loh  1
Affiliations

Feeding ecology and reproductive biology of small coastal sharks in Malaysian waters

Kean Chong Lim et al. PeerJ. .

Abstract

Small coastal demersal sharks form a major proportion of the sharks landed in Malaysia. However, little is known about their feeding ecology and reproduction. This study sought to elucidate the dietary patterns, role of ontogeny in prey consumption, and reproductive biology of four dominant small demersal shark species in Malaysian waters: the Hasselt's bamboo shark, Chiloscyllium hasseltii; brownbanded bamboo shark, C. punctatum; spadenose shark, Scoliodon laticaudus; and Pacific spadenose shark, S. macrorhynchos. Dietary analyses revealed a high overlap in prey taxa consumed; clear resource partitioning among co-occurring species based on the percentage Prey-specific Index of Relative Importance (%PSIRI), with higher fish %PSIRI for Chiloscyllium hasseltii, higher cephalopod %PSIRI for C. punctatum, and higher crustacean %PSIRI for both Scoliodon species; and an ontogenetic diet shift, seen through changes in prey size. Based on the examination of reproductive organs, the results showed larger sizes at maturity for males compared to females for all four species; no obvious reproductive cycles, based on hepatosomatic and gonadosomatic indices for all species; female bias in the sex ratio of the embryos of Scoliodon species; and increased reproductive output (number of eggs or embryos and size of eggs) with larger female size for C. hasseltii and Scoliodon species. The partitioning of food resources minimizes direct competition for food and supports coexistence within shared coastal habitats. The reproductive strategies of these small coastal sharks appear to be favorable for supporting short-term population productivity; although a reduction in fishing pressure, especially from bottom trawlers, is essential for the long-term sustainable use of these sharks.

Keywords: Diet overlap; Ontogenetic; Resource partitioning; Size at maturity.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1. Sampling sites around Malaysia with symbols indicating diversity of species sampled (number of species and individuals per species).
Black upward triangle, C. hasseltii; black downward triangle, C. punctatum; black circle, S. laticaudus; black square, S. macrorhynchos; grey circle, combination of C. hasseltii, C. punctatum and S. laticaudus; grey square, combination of C. hasseltii, C. punctatum and S. macrorhynchos; white circle, combination of C. hasseltii and S. laticaudus; white upward triangle, combination of C. hasseltii and C. punctatum. Size of symbols indicate sample size.
Figure 2
Figure 2. Size frequency distribution of the collected shark samples for reproductive biology.
(A) C. hasseltii, (B) C. punctatum, (C) S. laticaudus, (D) S. macrorhynchos. Dashed lines indicate maturity size for each species from available literature: Red, female; Blue, male; Grey, unspecified.
Figure 3
Figure 3. Maturity logistic regression for all sharks according to sex (female—left column, male—right column).
(A and B) C. hasseltii, (C and D) C. punctatum, (E and F) S. laticaudus, (G and H) S. macrorhynchos.
Figure 4
Figure 4. Observation of either congenital deformity or intrauterine cannibalism in Scoliodon macrorhynchos.
One underdeveloped embryo with deformed head.
See this image and copyright information in PMC

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