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Subject: Introduction and query re Hilsa
From: Doug Cross <[log in to unmask]>
Reply-To:Academic forum on fisheries ecology and related topics <[log in to unmask]>
Date:Mon, 29 Jul 1996 16:23:16 +0000

TEXT/PLAIN (25 lines)

Hello everyone! I am new here, and have to introduce myself to you. I am a zoologist, more recently (ie since around 1985) turned professional EIA practitioner and resource survey manager, and in the fishery sector have worked in fisheries and aquaculture in many different countries for over 30 years. I am especially interested in floodplain fisheries and in oil toxicology.
I have a question which someone may be able to help me resolve. Over several years recently I have been involved in EIAs on the lower Indus River in Pakistan and on the Narmarda River on the north-western coast of India. I have also worked on the fisheries of the Jamuna River in Bangladesh. All these rivers have an anadromous fish called locally either `Palla' or `Hilsa', which I believe is still known as Tenuallosa ilisha. The species is also reported to occur in the lower Euphrates.
The Arabian Sea stocks (in the Euphrates, Indus and Narmarda Rivers) appear to be under pressure from either changes in the flow patterns (Euphrates) or dam or barrage construction and abstraction (Indus and Narmarda). Whilst it is possible to deduce how the Hilsa stock in any one river may be affected by upstream developments or interventions, getting a clear idea of how the multiple interventions in all three of these rivers will affect the Arabian Sea stocks has been very much more difficult. Also, I have been unable to discover whether the Arabian Sea stocks are linked with that in the Bay of Bengal, so it is unclear whether or not a decline in one area would be either compensated by recruitment from the other, or might lead to a depletion of stock in the other area.
So, does anyone know whether
1.  there have been any studies on the dynamics of the Arabian Sea Hilsa, rather than simply studies of the spawning stocks in each individual river (if indeed even that has been done adequately), and
2.  the Arabian Sea stock is continuous and genetically identical with the Bay of Bengal stocks relying on the Jamuna system, or are they two separate geographically isolated stocks?
My concern is that there have been many local concerns about this species in Bangladesh, Pakistan and (to a somewhat lesser extent) in India, but no-one appears to have a clear idea of whether or not recent damage to the individual fisheries and their stocks may be masking a major threat to the stocks as a whole. Such a threat may extend either to the Arabian Sea stock alone, or to both the stock in that location and the other in the Bay of Bengal. Studies based purely on national interests and concerns do not appear to be addressing the wider question of the stability of the overall stocks.
Any information would be greatly appreciated.
--Doug Cross, Forensic Ecologist
Farthings, Higher Tale,
Payhembury, Honiton,
Devon EX14 0HJ, UK
Tel/fax (0044) 1884 277627
e-mail  [log in to unmask]

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