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.

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.

New database of marine aquaculture launched

The new Global Mariculture Database (GMD), released by the Sea Around Us Project, offers detailed information on the where and what of mariculture around the world since 1950. By mapping the production of marine aquaculture at smaller scales than the usual national scale and by digging deeper into the species being farmed, the GMD provides room for new insights into marine aquaculture.  And all of this information is now available online for anyone to browse on the Sea Around Us Project website!

The GMD confirms reports by the Food and Agriculture Organization of the UN (FAO) that the amount of seafood produced by marine aquaculture has tripled since 1950 – a massive increase. During this time, there has also been a shift in the type of seafood produced globally, with a larger percentage of predatory species, such as salmon and tuna, farmed around the world today compared to 1950. In the past, the relative production of species lower on the food chain, like mussels and oysters, was higher. This phenomenon has been described as “farming up the food web” a term derived from the concept of fishing down marine food webs.

In keeping with the Sea Around Us Project’s goal of improving public access to global fisheries and aquaculture information, this Global Mariculture Database (GMD) is freely available online at www.seaaroundus.org.

To find out more about the GMD and how it was created, you can read the paper recently published in the journal Marine Policy:

Campbell B and Pauly D (2012) Mariculture: a global analysis of production trends since 1950. Marine Policy 39: 94-100.

To everything there is a season

BC spot prawns (Photo: Island Vittles/flickr.com)

by Wilf Swartz

Japanese call it shun (旬), the seasonality of food. It refers to the time of year when a specific type of food is at its peak, either in terms of harvest or flavour. It is not unique to Japanese culture, as The Byrds reminded us in the mid-1960s with their, now classic, rendition of “Turn! Turn! Turn! (to Everything There Is a Season).”

Unfortunately, at least in our modern culture, shun seems to apply to many kinds of food, but not to fish. Although we do enjoy various seasonal foods out of season, often the associations are still there. Strawberries bring to mind the early days of summer. Pumpkins, especially in pies – and sadly, Brussels sprouts – trigger the whisper of falling leaves, thoughts of turkey and Thanksgiving. Yes, turkey itself is seasonal, although in medieval times it might have been venison instead, roasted over a roaring fire on a cold winter’s night. And the list goes on, and on, and on, for all but seafood, or most seafood, which has somehow fallen through
the cracks.

As for the ocean’s bounty, what is the best time of year to eat, or not to eat, herring or cod or tuna, or you-name-it? We’ve stopped viewing fish as seasonal.

And it’s epidemic. Living in Vancouver, which is more attuned to fish and fisheries than most other cities in Canada, many of us are aware when salmon is in season; yet, few of us would hesitate to order salmon rolls at a local sushi joint in the middle of February.

The reality is not that seafood lacks seasonality. In fact, as one of the few remaining, large-scale forms of hunting wild foods, marine fisheries are, without doubt, more susceptible to seasonal variations in productivity than other major food sources. We’ve simply found it convenient to overlook that fact for a number of reasons.

Fish stocks migrate in and out of local fishing grounds. Sometimes they are locally plentiful, and sometimes they’re not. During the spawning season, a fish’s body chemistry changes, e.g. fat content declines, and consequently for the consumer, flavour differs throughout the year. However, with the advancement of freezing technology and the expansion of global distribution networks [1], retail markets are now able to supply select species (and their close substitutes) throughout the year from all corners of the world. This, in effect, masks seasonal variations in local fisheries. Our seafood consumption has gone from “fish of the day” to “fish of whenever” and doesn’t take its bearing from the season.

Furthermore, there are benefits to eating seafood in season that we’re not reaping.

Ecologically speaking, sticking to seasonal seafood would enable fisheries to diversify their target species and distribute fishing impact more evenly across the underlying marine ecosystem. Such a balanced harvest strategy, it has recently been suggested, would be useful in mitigating the adverse ecological effects of fishing, even going so far as to support sustainable fisheries [2].

In terms of economics, matching seafood demand to seasonal availability could moderate the potential for price collapses associated with oversupply during peak catch seasons. By creating a situation in which fisheries could capitalize on the pent-up demand that accrues during periods of little or no catch, the additional supply during seasons of plenty would be absorbed by additional demand. Here the example of BC spot prawns comes to mind.

Diversifying the “portfolio” of fish species targeted by fisheries would also help to mitigate the inherent risks involved with specialized fishing, allowing the fisheries to better cope with fluctuations of specific stocks. Moreover, the promotion of seasonal seafood may present new marketing opportunities for fishes that aren’t “mainstream” and are currently treated as by-catch, thus further enhancing the economics of multi-species fisheries.

What about the benefits closer to home? A shift to consuming locally seasonal seafood would logically lead to consumption of local fish, which would have a positive impact on local fishing communities. The versatility required to shift target species and gears from season to season throughout the year is likely to favour small-scale fishing operations, which are generally perceived to be – though not necessarily – more energy-efficient and ecologically sustainable [3]. Rather than operating over a greater distance and following the migration patterns of targeted species, vessels could remain closer to their local fishing grounds, enhancing the socio-economic conditions of fishermen.

The issue is how do we promote such a major shift in our purchasing and eating habits?

“Seasonal” versions of consumer guides like OceanWise (http://www.oceanwisecanada.org/) and Seafood Watch (http://www.montereybayaquarium.org/) would be a start. And the feasibility of a seasonal seafood campaign and its effectiveness in promoting sustainable fisheries certainly needs to be investigated more closely.

But maybe the best science is no science. Yes, those left brainers, right brainers, or as we jokingly refer to them, “no brainers” may offer a key part of the solution. Eating what’s in season is a concept that intrinsically appeals to people at an emotional level. And the message should not be “eat the fish that’s in season for the ecological benefit,” but rather “eat the fish that’s in season for the emotional benefit.” In other words, because it will make you feel good.

For example, where was the chestnut industry, before a songwriter wrote, “chestnuts roasting by an open fire”? We need to find some brave, bold artist to write a song praising “pilchards pickled on a picnic table.”

All jokes aside, it is time to re-introduce the seasonality of fish into the social conscience and into local diets. The consequences of standing by idly are too terrifying to contemplate. Going back to The Byrds, “I swear it’s not too late.”

References
[1] Swartz W, Sumaila UR, Watson R and Pauly D (2010) Sourcing seafood from the three major markets: the EU, Japan and the USA. Marine Policy 34: 1366-1373.
[2] Garcia SM, Kolding J, Rice J, Rochet M-J, Zhou S, Arimoto T, Beyer JE, Borges L, Bundy A, Dunn D, Fulton EA, Hall M, Heino M, Law R, Makino M, Rijnsdorp AD, Simard F, and Smith ADM (2012) Balanced harvesting: reconsidering the consequences of selective fisheries. Science 335: 1045-1047.
[3] Pauly, D (2006) Towards consilience in small-scale fisheries research. Maritime Studies 4: 7–22.