Effective Management of Hilsa Shad (Tenualosa ilisha): Prevailing Research Trends in Bangladesh

Abstract

Aim: The purpose of this review is to support widely accepted knowledge based effective management of Hilsa shad populations through smart decisions.
 Study Design: Literature review of the population dynamics based studies along with the relevant papers of Hilsa shad fishery management in Bangladesh. Thus, accurate estimations of population size, growth parameters, mortalities and exploitation rates are critical for success.
 Place and Duration of Study: The literature review and other relevant documents are based in the coastal and riverine areas of Bangladesh during last three decades.
 Methodology: The review mainly included research findings on the catch and population dynamics of Hilsa shad in the riverine and coastal habitats of Bangladesh. This review comprised of published results on asymptotic length (Lµ), growth co-efficient (K), Growth performance index (ф’), mortality rates (natural-M, fishing-F and total-Z), exploitation rates (E), gear selectivity (Lc), maximum sustainable yield (MSY), standing stock or steady state biomass (SSB), average weight/length and length-weight relationship parameters.
 Results: The asymptotic length, growth co-efficient and growth performance index were varied from 51.5 to 65.6cm, 0.51 to 0.99 and 3.14 to 3.55 respectively. The variation of growth range was appeared from 21.19 – 37.69, 33.66 – 51.69, 41.0 – 56.89, 45.32 – 59.09, 47.86 – 60.79 and 49.36 – 62.52 cm at the end of age 1, 2, 3, 4, 5 and 6 years respectively. Simultaneously, natural, fishing and total mortality were varied from 0.89 to 1.52, 0.45 to 3.45 and 1.68 to 4.9 respectively. The exploitation rates were varied between 0.27 and 0.70, and the length at first capture were differs to be 39.24 to 57.65% of the mean asymptotic length. The overall mean length and weight value equal to 34.0±2.67cm and 540±120gm respectively. While the majority of the research papers (90%) indicated, overfishing, the annual catch of the species shows an increasing trend of 10,038 tons per year (R2=0.81) between financial year 1989-90 and 2018-19. The estimated MSY varied from 162396 to 283597, 283597 to 404798 and 404798 to 526000 tons from 60%, 30% and 10% studies respectively. The mean MSY value equal to 282174 ±100530 tons. Besides, three case studies showed deviations, inclusion of hypothesis based results and analytical gap. Thus, through the continual publication process the absolute unclear results maybe adjust or accepts in the national policy, including SDG-14s.
 Conclusions: The study indicated that the importance of science excellence, precise assessment and accurate estimation of the status of the fish stocks is vital for sustainable management of a fishery. Thus, the technical investigations need experience to analyze, predict results and produce fisheries management related suggestions, which is highly correlated to national or regional resource management decision.