On using catches to predict abundance

Factions among the fisheries community disagree on whether catch data – the amount of fish drawn from the sea – can be used to assess the health of fish stocks. In a comment piece published in Nature today, the Sea Around Us Project’s Principal Investigator Daniel Pauly shares his views, emphasizing that catch data are often the only type of data we have to tell anything about the status of fisheries.

While developed countries such as the US, Australia and those in Europe are able to use a variety of data, such as size, growth and migration information, as well as survey data, to conduct expert stock assessments, Pauly points out that these come at a cost: anywhere from US$50,000 to millions of dollars per stock. Such costs are not feasible for the majority of developing countries. Furthermore, for 80% of maritime countries, catch is the only data available.

In a second comment piece, Ray Hilborn and Trevor Branch from the School of Aquatic and Fishery Sciences, University of Washington, argue that there are other factors beyond the health of a fish stock that can account for changes in catch. Used on their own, catch data can create confusion and alarm about the abundance of fish stocks, they say.

Pauly agrees that catch data should be used with caution, but adds there is danger in undermining the value of this information. In most countries, the amount of fish caught is the only information available to assess stock health. “If resource-starved governments in developing countries come to think that catch data are of limited use, the world will not see more stock assessments; catch data will just stop being collected,” says Pauly.

The Sea Around Us Project, under the guidance of Pauly, is currently conducting a global evaluation of catch data, from 1950 to present, collated by the Food and Agriculture Organization (FAO) of the United Nations. Results so far reveal that many countries have underreported their catches. The extent of the underreporting is larger in developing countries (about 100-500%; Zeller et al. 2007) than in developed ones (30-50%; Zeller et al. 2011).

To see the full article, please go online to Nature.com: Pauly D (2013) Comment: Does catch reflect abundance? Yes, it is a crucial signal. Nature 494: 303-305.

Zeller D, Booth S, Davis G and Pauly D (2007) Re-estimation of small-scale fisheries catches for U.S. flag island areas in the Western Pacific: The last 50 years. Fishery Bulletin 105: 266-277.

Zeller D, Rossing P, Harper S, Persson L, Booth S and Pauly D (2011) The Baltic Sea: estimates of total fisheries removals 1950-2007. Fisheries Research 108: 356-363.

Jellyfish in the Mediterranean

Jellyfish (Cotylorhiza tuberculata) with juvenile fish near Hvar Island, Croatia. (Photo © Tihomir Makovec)

A new journal article from the Sea Around Us Project reviews knowledge of jellyfish in the Mediterranean Sea, including how the abundance of a number of native and invasive species has changed over time, and what could be causing the changes. In addition, the authors offer advice on how to manage jellyfish blooms – a challenge given the high levels of uncertainty and variability.

Lucas Brotz, a PhD student supervised by Dr Daniel Pauly, is the lead author on the paper, which is published in Acta Adriatica.

You can access the paper here.

Brotz L and Pauly D (2012) Jellyfish populations in the Mediterranean Sea. Acta Adriatica 53(2): 211-230.

A journey to South America

A fishing boat at Taganga, a village in Colombia. (Photo: Robin Ramdeen)

by Robin Ramdeen

In the first week of November 2012, the 65th Annual Conference of the Gulf and Caribbean Fisheries Institute (GCFI) took place in Santa Marta, Colombia. GCFI facilitates the exchange of experiences and ideas in fisheries science, management, governance, conservation and education. The conference was a testament to the region’s commitment to the stewardship of the Gulf of Mexico and the Caribbean Sea, and the marine resources therein. The Caribbean Sea is a special place for me, because I grew up in Trinidad and because I discovered my niche in Caribbean fisheries while doing my Master’s thesis on the fishing of queen conch in Tobago. The theme of this year’s conference was “Artisanal fisheries: importance, implications and challenges for management,” a topic which is familiar to many of us. Artisanal fishing is defined by the Food and Agriculture Organisation (FAO) as fishing carried out by individuals or households requiring low investment in technology and gear. By this measure, the majority of Caribbean fisheries operations are artisanal or small-scale.

The conference’s keynote speaker was Dr Ratana Chuenpagdee, who is no stranger to the Sea Around Us Project. Dr Chuenpagdee completed her PhD under Dr Daniel Pauly’s supervision in 1998 and is now the Canada Research Chair in Natural Resource Sustainability and Community Development at the Memorial University of Newfoundland, St. John’s. She urged the GCFI conference participants to consider ways to elevate the profile of small-scale fisheries, which – in terms of providing employment for fishers and catches for human consumption – are simply “too big to ignore” [1]. Dr Chuenpagdee is a powerhouse, and I was eager to chat with her at a socio-economic café where I got the opportunity to ask whether we erroneously mislabel our fisheries as small.

In terms of technological capacity, small-scale fisheries are certainly “small” compared to industrial ventures, but they are rather large in terms of the employment they provide for fishers as well as the quantity of catch they supply for human consumption [2]. Undoubtedly, the dearth of quantitative catch data associated with small-scale fishing sectors perpetuates this false notion of their size. As Dr Pauly plainly states in his foreword to the book “World small-scale fisheries: contemporary visions” (edited by Dr. Chuenpagdee), “countries cannot be bothered with the logistical and administrative nightmare that monitoring and reporting on small-scale fisheries often represents” [3]. As a native of the Caribbean and a research assistant with the Sea Around Us Project, I feel it to be my duty to reconstruct this historical fisheries information.

During my presentation at the conference, I explained how using information on catch, effort and seafood demand (i.e., consumption, as per household surveys) allowed me and my colleagues to reconstruct total marine fisheries catches for 10 Caribbean island countries from 1950 to 2010. Unsurprisingly, these catch reconstructions illustrated a substantial level of under-reporting in the Caribbean. For example, the reconstructed catches of Haiti and Jamaica were 3 and 4.3 times higher, respectively, than catches reported by these countries to the FAO, where the data become part of the world “catch” database. Overall, approximately 5 million tonnes of unreported catches were estimated for these 10 Caribbean countries during the 60-year period that we examined, with an average of 54,000 tonnes of unreported catches each year. The main discrepancy was due to unreported and under-reported catches from the artisanal, subsistence and recreational sectors. However, reporting seems to be improving as unreported catches in the early time period accounted for 80% of reconstructed catches, as opposed to 50% in the present time period.

The presentation was well-received and I had a number of scientists and fishers as well as an anthropologist interested in learning more about the Sea Around Us Project. Despite the English-Spanish language barrier, the GCFI spirit demonstrated that we are just one planet, working together for our precious oceans – questioning, sharing and improving things.

References
[1] “Too big to ignore” is a research network and knowledge mobilization partnership which aims to address the issues and challenges facing small-scale fisheries; http://toobigtoignore.net/
[2] Jacquet J and Pauly D (2008) Funding priorities: big barriers to small-scale fisheries. Conservation Biology 22(4): 832-835.
[3] Chuenpagdee R, editor (2011) World small-scale fisheries: contemporary visions. Eburon, Delft. 400 p.

Sea Around Us contributes to one of Smithsonian Magazine’s Top 10 Ocean Stories of 2012

The Ocean Health Index is the first global quantitative assessment of ocean health (Map credit: Halpern, et al, Nature)

In 2012, Kristin Kleisner, Dirk Zeller, Rashid Sumaila and Daniel Pauly with the Sea Around Us Project were part of an international team that undertook the first global comprehensive assessment of ocean health – and gave it a passing grade of 60 out of 100.

This achievement – the first “grading” of ocean health – has been recognized as one of the top 10 ocean stories of 2012! You can read more about this research and the other top ocean stories highlighted by Smithsonian Magazine here.

Find out more about the Ocean Health Index at this website and see the paper published in Nature.