Population statistics of the migratory hilsa shad,Tenualosa ilisha,in Sindh, Pakistan

Abstract

Summary In order to estimate the population dynamics of the hilsa shad, Tenualosa ilisha, fishery in Sindh, the key population parameters of growth, mortalities, recruitment pattern, exploitation and maximum sustainable yield are discussed. Length frequency data were collected from April to October 2004 from the main commercial (hilsa) landings at Thatta, Sindh. Estimated parameters of the von Bertalanffy (Hum. Biol. 10, 181–213) growth model were L∞ = 31.5 cm, K = 1.5 year−1, t0 = −0.10 year as obtained by the electronic length frequency analysis (ELEFAN I). Estimated natural, fishing, and total mortalities were 2.21, 0.673, 2.89 year−1, respectively. The relative biomass per recruit (B′/R) was 0.95 and yield per recruit (Y′/R) was 0.06 using the knife‐edge selection. The exploitation ratio at the maximum sustainable yield (MSY) was Emax = 1.0 year−1, fishing mortality at MSY was Fmax = 2.89 year−1, average target Fopt = 0.5 year−1 and Flimit = 1.47 year−1. The catch and effort data from 1981 to 2004 (MFD, Karachi) were analyzed using the catch and effort data analysis (CEDA) computer programme. Estimated biological reference point of MSY for the Fox model was 891 tonnes (t), R2 = 0.75; for the Schaefer and Pella‐Tomlinson models MSY = 744 t, R2 = 0.49, the outputs of which appeared to be more conservative than the Fox model which indicated a better fit. The overall situation of hilsa fishery is in severe stress and appears vulnerable to overexploitation. On the basis of the present findings, serious attention is required to provide appropriate access of the fish to the Indus River during the spawning period as well as to impose a ban on fishing during upstream migration and on undersized catch to prevent this traditional fishery in this area.

Tropical hilsa shad (Tenualosa ilisha): Biology, fishery and management

“…An increasing trend in total catch since 2004 could be the outcome of well‐enforced seasonal ban in fishing hilsa brood and juvenile stocks, though segregation of individual initiative's role in the catch of an anadromous species is difficult. Hilsa is a highly preferred edible fish to millions of people living in the Asia and the Middle East countries due to its taste, flavour and delicate culinary properties (Alam, Mohanty, Hoq, & Thilshed, ; Almukhtar, Jasim, & Mutlak, ; Miah, ; Panhwar & Liu, ). The market demands of high‐quality fish in the Middle East, Europe, North America, Japan and Australia have stimulated the hilsa price in recent years.…”

Population Parameters of Siluroid Catfish (Eutropiichthys vacha) from Indus River, Pakistan

“…The total length and total weight of the fish samples was measured to the cm and g with an average of 21±4.329 cm TL and 71±39.911 g TW (n= 821) for combined sexes, while 21±4.274 cm and 67±37.703 g (n= 459) and 22.035±4.247 cm and 75.295±43.473 g (n= 362) for male and females respectively. The Provincial Government of Sindh allows a minimum mesh size of 15 cm for the capture of adult fish but, unethically, this mesh size is ignored (Panhwar and Liu, 2013). For medium fish, the most effective mesh size is between 3-4 cm.…”

Length-based estimates of growth parameters and mortality rates of fish populations from a coastal zone in the Southeastern Brazil

“…Direct readings of hard structures (e.g., otoliths, spines, vertebrae) to estimate the age of fish, or indirect estimates based on length distribution data over time are traditional methods to determine growth parameters of fish populations (Gayanilo et al 2002, Panfili et al 2002. Indirect stock assessment tools are relatively more useful in tropical and sub-tropical waters since hard structures in these relatively warm waters, where seasonal differences are subtle, often present unclear band marks Venema 1992, Panhwar andLiu 2013). The development of the length-based stock assessment methodologies and relative growth models (Huxley 1993), simplified the investigation of population dynamics of fish stocks in tropical waters (Froese and Binohlan 2000).…”