I am not a person to venture with an answer to this question to an expert in this field. I feel still that certain ways could be thought of impact assessment of small scale fisheries inn an estuary. If overdone this fishery will lead towards depletion.

Socio-economic survey may be required in the first place. How many fisher persons depend on the estuary. How much per person area (in ha) is available in the estuary on average. Through field sample survey it needs to be ascertained how many fishing days collectively are happening in the limited area of the estuary.

Of the commercially important fishes what is the average effort for fish catching and what the returns are, in terms of species-wise average size and quantity caught. Is there any reduction in size classes and quantities of fish caught over the last many years (through interviews)? Is there any change in mesh size of fishing nets? What is the current management regimes to govern fishing? If there is none could it not be a reason for non-sustainable harvest- if the same is happening? Whethehr the demand for estuarine fish has increased? Whether the markets have expanded to cater to wider circle of consumers? All these could be the first be to gathered before devising next set of questions.

Dr M D Subash Chandran

Dear Mayank

         Fishing pressure beyond the natural carrying capacity is considered as one among many human abuses for the open water fisheries. Fishes are exploited at every stage of life from post larvae to table size adults and estuaries suffice as significant resource for this purpose. Following the increase in demand and excessive exploitation of consumable fishes and so also the stocking materials for aquaculture practices, the fish and seed resources of the estuaries came under hardpressed conditions since seventies. Decline in quality and quantity of shell and finfish seeds in Hooghly estuary due to over-exploitation has been reported by Bhaumik, CIFRI. Similar effect has also been observed in Mahanadi estuary by the scientists of CIFRI. Besides detrimental effect on seeds, the overexploitation of fishes irrespective of size and season has significantly affected the quality and quantity of annual turn-over of fisheries in almost all the estuaries of the country. Further, the deployment of non eco-friendly gears with smaller mesh size has attributed severely to the cause of decline in fisheries.

         The impact of fishing in the estuaries can be assessed by studying : target organisms, non-target organisms, nursery functions, trophic effects, habitat change, reduced water quality, human environment, and extinctions including socio-economic conditions of the fishes. Catch per unit efforts to be compared with past.

         Further, I would suggest you to read a book entitled 'Indian Estuaries" very recently published by Hindustan Publishing Corporation, New Delhi. 

I would like to see a though discussion of this very important question. If someone asked how we should assess the impact of fishing in a large-scale, temperate, offshore fishing ground, there would be clear answers  -- though the uncomfortable truth is that the results of such an assessment would be surrounded by massive uncertainties. When the question is asked with reference to small-scale fisheries in a tropical estuarine system, we must confront much, much greater challenges. I am not convinced that there are any solutions yet, though I will be interested in seeing what ideas others can offer here.

I think that Dr Subash Chandran may have offered two valuable approaches already. If it is impossible to assess the impact of fishing with useful accuracy, then there is no point in wasting resources on what cannot be done. Instead, we should ask a different question. A socio-economic survey might reveal the problems faced by human communities that are dependent on the estuary, in which case those problems could be tackled directly, without necessarily knowing the impacts of fishing on the ecosystem. Alternatively, looking for changes in fish, fishing and the fish trade might show stability (indicating that the existing system is meeting people's needs) but is more likely to show change. The challenge then would be to disentangle the inter-related changes and determine which are the driving factors. For example: external forcing (e.g. sediment run-off) could be driving environmental change and so affecting fish availability, fishing could be depleting the resources, changes in consumer demand could be causing fishing practices to shift, and so on.

Dear colleagues,

Although I have not the solution I would like to give you some information concerning the approach of one of the FAO project I was invoved. As its not an easy task involvement of fishers from the beginning is esential, particularly when trying to stablish real production, fishing effort or to know where and when fishers are working. Project ArtFiMed (see link) was organised in phases to better know the SSF situation in two countries Morocco and Tunisia (Mediterranean Sea): first phase was a diagnosis, based on surveys conducted, that included biological, economic and social questions. During the secon phase it was possible to elaborate a Monitoring system and define (with the fishery actors) five focus areas (themes) requiring follow-up through indicators: 1. Significant fisheries for the selected site, 2.Socio-economic aspects of fishing communities,, 3. Fishery products marketing, 4. Professional organization Systems and 5. Environmental aspects associated with the fisheries. Of course that you need to agree the most feasibles indicators. Third we implemented the Monitoring system with the participation of the fishers and gfinally with the data obtained we were able to produce valuable information for the assessment of the main ressources: C, f, Production, marketing, fishing areas, etc. You can have the technical reports with metodologies and indicators selected in the Web page (see below) particularly under "Publications"

You can be also interested in the FAO experience with artisanal fisheries in Africa (Sustainable Fisheries Livelihoods Programme (SFLP) or in Asia  through the Fisheries Livelihood Program (see link), where you can consult different documents.

http://www.faoartfimed.org/

http://www.faocopemed.org/

http://www.fao.org/fishery/rflp/en

Dear Pandey,

This is a very nice question which, as Trevor put it, may not be easy to answer!

I think we should start from the basics. Tropical estuaries are know for being productive fishing grounds--especially for prawns and other nursery species. These same waters are known to be nurseries for many coral reef fishes and actually there is voluminous literature about their importance as critical habitats for juvenile fish species.

So, although the estuarine habitats are important to that magnitude, they are threatened by unsustainable fishing activities, such as beach seining. The impacts of such activities are many and can be assessed from different perspectives. For example, we now know that the world's fisheries are declining and not keeping up with population growth and urbanization. If you have long term trend is fisheries catches and effort data, you can assess the impact of fishing by looking at the trend--which I will guess will de declining. You can also study the fisheries by sampling length and weights of fishes landed in from the estuaries. compare that with historical data, you may note that there is a tendency to catch small sized individuals over time, which should show you that things are not OK. You can also look at the habitats, degraded or fragmented. For areas with rampant beach seining, the sea bed will be very damaged. If there are patches of seagrass, they may be in very bad shape or disappeared. Looking at the catches, you can also note that the inputs do not necessarily result into better catches - and this should show you how much the fishing is affecting the estuaries.

Then you can conduct a socio-economic survey using questionnaire and focus group discussions as a barometer for increased or decreased provision of goods and services by the estuaries.

For a sustainable fisheries, one that is cognizant of the habitat and its importance, you will find that fishes caught are of good sizes while the habitats are relatively in good condition. The communities also will be enthusiastic about the services that the habitats are providing. The opposite will be true for a fishing that is oblivion of the ecosystem.

Hope this helps!

Ishmael

Could you be more specific about the type of impact you are interested in?

dear mayank,

if you are looking at assessing ECOSYSTEM impacts by fishers and fishing in an estuary, i think a good point would be to start identifying the ecosystem components you want to look at, and eliminate issues that are unrelated to your question (e.g. social and economic aspects). in simple terms, to me these components are:

a) the bio-chemo-physical estuarine habitat itslef (incl. functions such as nurseries)

b) the fish stocks and related fauna (foodweb)

c) the riparian environment (erosion, pollution, deforestation, etc.)

then i would try to estabish relevant baselines for your estuary, using literature and/or reference ecosystems that are in more or less pristine conditions. on the basis of this work, you will determine quite easily which factors will be relevant to sample, to quantify, and to determine environmental impact.

likely impacts ought to be quantified for the fish populations themselves, impact on related species in the foodweb, impacts on benthos and other habitat components, impacts on the riparian environment by implanted fishing communities (fire wood collection, erosion of banks, pollution, etc.) - and how those impacts may affect ecosystem components beyond the estuary (e.g. what is the net effect of the destruction of a shrimp nursery on the inshore commercial fishery outside of the estuary?).

hope this helps!

best wishes,

g

Well from a food web point of view,  you need to know what the fish eat and what the seabirds who eat the fish eat. You also need to have an idea of the amount of fish necessary to sustain a population of seabirds in the area where the fishery occurs. Knowing the latter, and how much food from those fish is needed in order for the chicks to be able to fledge. Likewise, in an estuary, you need to figure out how the primary producers' chemicals (e.g. from the diatoms) are going to be transferred up the food web to the other vertebrates. If there is a break in the food chain because of overfishing, you have a real problem. Ditto if you do not have enough fish for the seabirds to raise their chicks to fledging or to sustain their regular populations in an area.

Concerning the answer by Gilles, we should consider that the question possed by Mayank is "How to asses Impact of Fishing in tropical estuarine ecosystem where small scale fisheries practiced?

So if the impact of fishing is the key point I dont see how you can eliminate the associated socio-economic issues, mainly because fisheries are driven by economic forces, also SSF.

Each day in past 10 days I spend few hours in mouth of Mabini (Balincaguing) river (coast of South China Sea, Philippines, province of Pangasinan, Aloleng city).

Here there are many local people who engage in small scale fisheries.

And I see only few fishermen, who catch fish in the estuary. But there are lot more of them, who catch fish in open sea waters. I think in this particular case the subject of main impact of fishery are coastal waters.

thank you to all Respected scientist