Genetic population structure and recruitment patterns of three sympatric shallow-water penaeid prawns in Ungwana Bay, Kenya, with implication for fisheries management

Abstract

Penaeid prawns in Ungwana Bay, Kenya, are heavily exploited by artisanal fishers and industrial bottom trawlers. Human activities in mangrove and estuarine areas may affect prawn nursery habitats and influence juvenile recruitment to fished areas, therefore it was important to investigate recruitment patterns in the bay. To test the hypotheses that single genetic stocks exist, we utilised a combination of mtDNA sequence and microsatellite data. Three dominant sympatric species, Penaeus monodon, Fenneropenaeus indicus and Metapenaeus monoceros were targeted. Sample sites were chosen to represent the bulk of fishery activities, and included estuarine juveniles and offshore adults. An exceptionally high mtDNA haplotype diversity, coupled with low nucleotide diversity was observed for all three species and there was no genetic differentiation among sampling sites. Genetic panmixia was confirmed by the microsatellite analyses of P. monodon. Juveniles that recruit to adult populations in Ungwana Bay most likely originate from local estuaries, and conservation of the prawn nursery habitats along the edges of the bay is advocated. Each of the three species represents a single management unit, and the identification of spatial management strategies to mitigate resource-user conflicts should rather consider other ecological and socio-economic factors than the genetic delineation of stocks.

Mitogenomic variation of Bangladesh Penaeus monodon (Decapoda, Panaeidae) and reassessment of its phylogeography in the Indo-West Pacific region

“…The high haplotype diversity in Bangladesh is similar as observed elsewhere in the Indo-West Pacific region where it ranges from 0.97 to 1.00 (You et al, 2008;Zhou et al, 2009;Waqairatu et al, 2012;Mkare et al, 2014). The nucleotide diversity (p) in Bangladesh is also comparable to the most samples with a single CR lineage, and it is close to the average of the samples characterized with the C lineage but nominally lower than within the samples characterized by the A lineage, south and east of the Sunda Shelf (Table 3).…”

“…High genetic diversities have also been reported in P. monodon populations from the Indo-West Pacific region (You et al, 2008;Zhou et al, 2009;Waqairatu et al, 2012;Mkare et al, 2014). The distribution of the mtDNA variation along the Bangladesh coast does not provide any evidence of population structure, reflecting a random mixing of pelagic larval stages and or migration of adults.…”

“…In total, 840 sequences for the CR of P. monodon, including 754 from GenBank and 86 from Bangladesh, were used to reconstruct the mtDNA phylogeny. The sequences were aligned using ClustalW Multiple alignment of Bioedit Sequence Alignment Editor (Hall, 1999) and were trimmed to 496 bp fragment, the sequences from the study of Walther et al (2011) and Mkare et al (2014) were aligned for 225 bps. The sequences of the CR were classified into the different lineages (A, B and C), as defined by Zhou et al (2009) and Walther et al (2011), by constructing a maximum likelihood tree with partial deletion treatment for missing data and a general time reversible (GTR) model with gamma and invariant sites parameters (G?I) in MEGA ver.…”

“…Three hundred and eleven sequences were obtained when omitting Indonesia and 337 sequences when including Indonesia. The phylogeny included 12 CR sequences from Kenya (You et al, 2008), and the shorter sequences from Mkare et al (2014) were omitted. Fenneropenaeus chinensis was used as an outgroup for all analyses described above.…”

“…The geographic patterns in variation of the CR were evaluated using 714 sequences from lineages A, B and C, and, separately, for 337 sequences from the C lineage (excluding the shorter sequences from the study of Mkare et al 2014; see Table 1; Appendix 2). For both analyses, pairwise genetic distances (U ST ) based on the 496 bp fragment were calculated and tested by 1000 permutations using ARLEQUIN v3.5 (Excoffier & Lischer, 2011), except for comparisons with the Indonesian samples which were based on 225 bp.…”