Population biology and stock status of planktonic shrimp Acetes indicus (Decapoda: Sergestidae) in the coastal waters of Malacca, Peninsular Malaysia

Abstract

Reproductive cycle, growth, mortality and exploitation rate of Acetes indicus were examined in the coastal waters of Malacca, Malaysia between February 2005 and March 2007. Monthly length frequency data were analyzed using FiSAT software for estimating population parameters of A. indicus, including asymptotic length (L∝), growth co-efficient (K) and exploitation rate (E) to assess the status of the stock. The annual mean L∝ and K for males were estimated at 29.93 mm and 1.60 yr−1, and for the females were 40.95 mm and 1.20 yr−1. Mean growth performance index (φ′) was calculated as 3.15 and 3.31 for males and females, respectively. Maximum life span (tmax) of males and females was 1.88 and 2.50 years. Total mortality (Z) by length converted catch curve was estimated at 4.30 yr−1 for males and 3.62 yr−1 for females. The rate of natural mortality (M) for males and females was calculated as 2.54 yr−1 and 1.93 yr−1, and the fishing mortality (F) was 1.77 yr−1 for males and 1.70 yr−1 for females. Recruitment pattern of A. indicus was continuous throughout the year with two major peaks. The exploitation rate (E) of males was 0.41 and that of females was 0.47, though the exploitation rates were slightly less than the optimum level of exploitation (E = 0.50). Thus, the stock of A. indicus is under pressure in the coastal waters of Malacca, Malaysia.

Population parameters and the relationships between environmental factors and abundance of the Acetes americanus shrimp (Dendrobranchiata: Sergestidae) near a coastal upwelling region of Brazil

“…The relatively greater length of A. americanus females has been corroborated by other studies on Acetes species (Table 4), which argues for the existence of a standard of sexual dimorphism in terms of size JEONG, 2003;ARSHAD et al, 2008;AMIN et al, 2009a;AMIN et al, 2012;SIMÕES et al, 2013a). In studies on other At a depth of 15 m, the average temperature was 20.7 ± 1.8º C, with a variation from 18.0º C to 24.5º C; salinity varied from 35.0‰ to 38.0‰, with an average level of 36.9 ± 0.8‰.…”

Length-Weight Relationships of Acetes spp. Sampled Along the West Coast of Peninsular Malaysia

“…Differences in growth patterns were, however, observed between males and females of A. japonicus whereas the pooled data of both sexes for A. sibogae showed positive allometric growth as compared with isometric growth in the case of individual sexes (Table 3) aquatic samples with narrow size ranges (Froese 2006;Froese & Pauly 2011;Jobling 2002). It is hypothesized that these b values in female Acetes shrimps could also signify individuals that have spawned their eggs and are thus longer in relation to their weight (b <2.5) or ovigerous females with mature, unfertilized eggs that are heavier relative to their lengths (b >3.5) (Amin et al 2009b;Froese 2006). Furthermore, the availability of food resources and favourable environmental conditions at a particular location might play an important role in determining the allometric growth type in male and female Acetes shrimps (Wong 2013).…”

“…This is similar to earlier studies of LWR of Acetes spp. in the coastal waters of Malaysia (Amani et al 2011;Amin et al 2009bAmin et al , 2009cArshad et al 2012Arshad et al , 2008Arshad et al , 2007, Bombay (Deshmukh 2002), Western Australia (Ikeda & Raymont 1989), Guangdong, China (Lei 1988), Inland Sea of Japan (Uye 1982) and Bangladesh (Zafar et al 1998a, (Tables 3 & 4). As for A. japonicus and A. sibogae, the males showed an isometric growth type.…”

“…spawning and pre-spawning Acetes aggregations (Omori 1975;Wong 2013). This is because Acetes species have spawning peaks twice a year which follow the monsoon seasons (Amin et al 2009b(Amin et al , 2009cOh & Jeong 2003) and undergo seasonal migration between shallow inshore and deeper offshore waters at different life stages (Chiou et al 2000;Omori 1978Omori , 1975.…”

“…Previous studies on Acetes focused mainly on the distribution, morphology, reproductive biology and morphometry studies (Amin et al 2010(Amin et al , 2009a(Amin et al , 2009bArshad et al 2008Arshad et al , 2007 based on inshore catches using traditional fishing gears. However, the majority of Acetes landings are from offshore trawling activities (DOF 2010), but the length and weight relationship data of this genus remains scarce.…”