in our area there was a decrease in fish abundance, at least in case of those of economic importance

for the moment I can indicate only the copy of some articles in Romanian language ( one at: http://www.ddni.ro/manager/editor/UserFiles/File/Scientific%20annals/volume/4.1/29.pdf ; the other one at http://www.ddni.ro/manager/editor/UserFiles/File/Scientific%20annals/volume/7/13.pdf ), but I will try to identify the ones published in English

p.s. as I recall, there were works on the fish-length and weight values along time in various lake-systems (even if they are not classic fisheries...)

I don't know much about artisinal fish markets, but the mention of trophy photos reminded me of the "tourist places" maps produce from Flickr data. Considering the amount of sport fishing in my area, I imagine that trolling (pun intended) photosharing websites for trophy photos might be a cool way to judge abundance.

http://www.flickr.com/photos/walkingsf/sets/72157624209158632/

You might be interested by this article dealing with fish "landings" and hypothesis about fish stock evolution.

http://www.ncbi.nlm.nih.gov/pubmed/19189235

We conduct a similar study, but in the fishing ports of Favignana and Marettimo in the Egadi Islands. Initially, we defined the typology of fishing practised by the boats of the fishery of Favignana and Marettimo (artisanal fisheries), to characterize the most utilized gears and the species caught most often. From these, we selected the “target species” for our analyses to qualify the fish products of the Egadi Islands. The target species, Scorpaena porcus (Linnaeus, 1758), Scorpaena scrofa (Linnaeus, 1758), Palinurus elephas (Fabricius, 1787), and Sepia officinalis (Linnaeus, 1758), were caught in the typical areas used by local fishermen of Egadi Islands, by trammel net, during the months of June and July 2003.

I attach this paper for consultation

No, but it's something I thought would be really interesting here in China and would love to get into. Fish are sold at every street corner here. There would be some really cool data I'd say.

Matt, I like your idea. Cool way to gather data. Would be interesting to look at fish condition trends over time. The hardest thing would be standardising the photos - if only they all took a photo with a ruler next to them! Re: abundance, the issue would be an increase in use of sites like flickr over time.

Most stock assessment and population abundance studies in India use samples from commercial fish landing centers (which is a whole sale market). However, for species with low value and those restricted to inshore fishery, samples from local markets are used (most of these will be artisanal).

Fishery independent data is not usually collected and incorporated in research studies (for most cases) due to lack of resources (Research Vessels).

Fish length and weights are collected using a stratified random sampling and scaled to estimate total landings. Length frequency data is used for stock abundance studies. The methods followed are mostly applicable to tropics (eg: http://www.fao.org/docrep/W5449E/W5449E00.htm)

You might need to know the fish assemblages of the reservoir(s) of the area prior to your study in order to measure the exploitation rate of the fish species considering the catch statistics from the market.

Isn't there a problem in estimating exploitation from catches? I guess fishermen will fish where the fish are, irrespective of the abundance. If so, you will first notice a change when the situation is really bad and the market size fish is almost completely depleted (like when the cod collapsed in the W. Atlantic Ocean). Of course, some data is better than no data, but indications of over-exploitation may come too late.

There was recently a discussion in Nature about using catch data: http://www.nature.com/nature/journal/v494/n7437/full/494303a.html

Not quite artisanal and a bit dated now, but...

http://www.nova.edu/ocean/ghri/forms/clarke06.pdf

Hi,

It's not my field of research at all but if I'm not completly wrong, Daniel Pauly and colleagues published papers about this topic where they used records of catches on markets in the UK during 18 and 19th centuries to assess population size changes during the 20th century...

It should be mentionned at least in this book (In a Perfect Ocean: The State Of Fisheries And Ecosystems In The North Atlantic Ocean) and some wise people might recommend other published articles.

HTH

As far as I know the variables you already described are the ones that can be obtained using information from fish markets. Categorization of marketed species (due to abundance, price or preference). I used this once in order to test a negative impact in landings and composition from particular zones due to an oil spill event, but this must be supported by official landing statistics.

You may wish to present your question to the Listserve of the Gulf and Caribbean Fisheries Institute. You should receive responses from those that utilize fishery-depenndent data from artisanal fisheries. It is a very active listserve for the Caribbean and Latin America: [email protected]

We conduct a market survey every 2 weeks for mangrove crabs - Scylla serrata and a variant of this, Scylla serrata var. paramamosain. We talk to all vendors present at the time of survey and collect data on carapace width, weight, price, sex, whether the crabs are molting or not, for females - whether they are berried or not, harvest locality, habitat of harvest, gear used, number of fishers, duration of fishing trip, distance from home to harvest site, personal consumption of crabs and number of years as mud crab vendor. The premise of this study was to gain an idea of resource exploitation as a means for resource management efforts in the areas where these crabs are harvested.

We did this type of research a couple of decades ago in the Philippines but used only the market survey for an initial identification of species and getting some samples. There are too many variables involved data from vendors are used as an estimate of biomass or exploitation rate because of the variability in fishing effort, particulars of fishing gears, source of the fish (it may have been bought through middle men, etc). One way to improve your data is to interview the fishermen themselves as they may have records or estimates of catch over a period of time and complement that with the data you get from the vendors. Our report can be found at:

http://books.google.co.nz/books?hl=en&lr=&id=cmGkS9lQSm4C&oi=fnd&pg=PA3&ots=T7jUCzU12r&sig=dq8Oe19d0GIdliIghCpIiK_H64A#v=onepage&q&f=false

Using the data on length and weight of fish you can estimate the exploitation rate by analyzing it using FISAT (FAO-ICLARM Stock Assessment Tools) you can obtain the optimum exploitation rate and other growth parameters..

Assessment of exploitation rates and/or fishing pressure and estimation of biomass (read stock assessment) can be conducted using market data and using what we call indirect stock (read fishery) output assessment based on estimates of consumption and the seafood trade via socio-economic surveys of the fisher / hunter communities within the fishery under assessment. I am sure some collaborative approach to your problem analysis with statisticians and fishery experts should get you of the stalemate. Feel free to link up for the analysis if you get stuck on the analysis approach, kindest regards

Well the only way to know what are the fisheries targeting is to investigate either landings (with the parameters you defined and alternatively age data) or fish market samples. It is in North Europe used for stock assessment. It is nice to characterize your wild exploited population but you need to know how this relate to fisheries if you are to detect any impact of them. A change in age class in the catches, if not due to a change in the fishery area is likely to tell you that something is going wrong with your population (if mean age is going down for example).

Tenho usado espécies de mercado ao longo do tempo apenas para verificar substituição ou troca de espécie desembracada, com isso, sugere-se que algumas espécies são ou já foram mais pescadas durante anos de estudos. Os dados utilizados são de estatisticias de desembarque e de acompanhamento no proprio mercado de peixe

I am agree with Bart Adriaenssens

Fishing location and selectivity of fishing gears would make an error in your calculations.

Dear James, Thanks for posting your question. I found this for you which may be of help, i hope.

Best wishes,

Ram

Hi, In Poland not, because commercial fishery collapsed already, but in Brazil, in Parana state, yes. Included is e-mail address to Brazilian professor who is familiar with this subject (>[email protected]< Prof. Angelo, Antonio Agostinho, University of Maringa, NUPELIA, Maringa)

Yes in sea cucumbers, where the data on the fisheries are often not accessible, the surveys of the markets (particularly chinese) are interesting and helpfull.

Chantal Conand

All this is fine, as long as you don't forget that fish biomass and, hence, its exploitation rate depend also on environmental fluctuations, often predominantly, including availability of food and predation pressure. The whole system is very dynamic, and collected markets' data alone, can't give sufficient information on the stock size and condition. Lots of info you can get from fishermen, especially the older one, who can tell you about changes and fluctuations in the past. MB-Y

To determine the exploitation rate you'll need a lot of information from the fishermen like the type of fishing gear, the mesh size, how far out to the rivers or lagoons do they explore for fisheries, the average number of boats that supply landed fisheries to the fish market, the seasonal appearance of species and abundance and varieties of species.

These data are very important for determining exploitation rate and modelling future trends if intended.

To determine biomass, biological indices like length-weight frequency data, and computation of condition indices like relative weight (Wr) across seasons.

You could look at recent work on freshwater crayfish in Madagascar by Jones et al. - they used market offerings among other evidence to investigate pressures on stocks. e.g. Jones JPG et al. 2005, Conservation Biology 19; Jones et al. 2006, Oryx 40. Best wishes, Julian Reynolds

Hi,

We used the fish market. You may check the ms which is Akyol,O., Ceyhan, T., 2007. Exploitation and Mortalities of Bluefish (Pomatomus saltatrix L.) in The Sea of Marmara, Turkey Journal of Applied Biological Science 1(3): 25-27

http://nobel.gen.tr/Makaleler/JABS-Issue%201-29-2011.pdf

We carry out experiments with chilean kelps, but our experience with local fishermen could be applied for several marine resources. If you are going to use information from national statistics (landings), you should ensure if data are not overestimated or subestimated, since these are very common practices from fishermen to avoid penaltys (fines) in case of overexploitation. better options could be answer directly in fishery location for their particular landings or take samples by yourself, and then compare with national statistics

Any information beats none. Seeing trophies decline in size and frequency over time, talk to older fishermen, get a feeling for length frequency, total catch, that kind of thing. Determine if there is size overfishing and to what extent. LEK is a great place to start, and finding out where fish are landed and when is another, along with a histogram. You would be amazed what is used in The Ghana to get a handle on the fishery there.

For information regarding artisanal fisheries in the Caribbean region, I suggest that you post your inquiry on the Listserve of the Gulf and Caribbean Fisheries Institute ([email protected]). This active Listserve is composed of fisheries scientists and managers that work with artisanal fishers and co-management.

I have never used fish market data for this kind of survey, but I did have interviewed fishermen about fishing arts and techniques, and also about changes in both ichthyofauna and environment along the past years in a given estuary located in northern Brazil. However, I am still not sure how to cross such qualitative data with those as observed in the wild...

I have one publication on this theme, hope it may be useful.

Catch Assessment Surveys are expensive and manpower intensive. I worked on a reservoir in Northern Cameroon (Lagdo) on frame survey and CAS data. Quite a complex fishery with many tribes using different gears and methods. Interestingly, due to the lack of roads around the lake, all processed fish arrived once a week at a certain village for further transport to other regional markets. We conducted a CAS and a market sampling survey at the same time for an extended period of time and we found that the difference in estimates was negligible. In case there are very few markets around a lake, and practically all fish is channelled through these markets, the market sampling would suffice. Of course, such figures would not give you biomass data, but after a certain number of years a trend will become visible.

We got a snapshot of a tri-national fishery in the Gulf of Honduras using comprehensive fisher interviews. Using the data, we were able to offer estimates of catch rates by species, gather opinions on the causes of observed declines and suggestions for their mitigation and reversal. Perhaps most importantly, by giving the analyzed data back to the participants in the form of a full-color booklet "The Voices of the Fishermen" we were able to draw more fishermen's trust in the process and collaboration in fisheries management.

A paper, documenting the process and results of the voice of the fishermen is:

Heyman, W.D. and P. Granados-Dieseldorff. 2012. The voice of the fishermen of the Gulf of Honduras: Improving regional fisheries management through fisher participation. Fisheries Research 113(1): 129-148.