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Into the tuna can – an insight into sustainability

To be honest I attended a recent presentation on some background into the tuna industry with the preconceived notion that I would leave swearing never to buy another tin of tuna and never include it again in my nutrition plans. The workshop was offered by John (JD) Filmater who completed his PhD looking into some of the sustainability issues that are present in the tuna industry, specifically the impact on the silky shark population. The discussion promised to give some insight into how tuna arrives on our grocery store shelves.

I walked away somewhat surprised.


There are 5 species of tuna that are fished in the oceans of the world, most of the 4.5 million tonnes is caught between the tropics. These species include skipjack, yellowfin, bluefin, bigeye and albacore (known locally as longfin tuna). Each species presents different and unique characteristics such as rate of growth, age of reproduction, population number, size and life span which all impact their sustainability profiles.

Bluefin tuna are the prized catch, growing well beyond 200 kg, 2 meters long and fetching hundreds of thousands of dollars per fish. Their numbers are small, so too is their catch although in value it is likely to make up most of the fishing industry. In conjunction with a slow reproductive cycle the sustainability of bluefin fishing is currently poor.

Yellowfin tuna is the species most likely to be on your sushi platter although catch numbers are small. This is the game fish we find often along our coast line along with albacore (longfin).

The remaining three species make up the majority of the tuna fishing industry and are the three species you will generally find in a can. Skipjack is the smaller tuna and reproduces quickly. Catch numbers are huge and by far the most of all 5 species. Bigeye and albacore are slightly bigger, longer living fish that reproduce a little slower than skipjack. This rate of reproduction is one critical element in the evaluation of sustainability, the quicker each generation can produce another to take its place the better the chances that they can sustain the worlds vast hunger for this quality protein. For these reasons skipjack is one of the most sustainable fish in terms of numbers. We have yet to see a year where the catch has been smaller than the last since 1950. Their stocks in the ocean are handling our need for food, for now.

The main concern with the tuna fishing industry seems to be with the methods used to land the fish. The issues centre around the by-catch, or the catching of sea life that is not the main target of the fishermen. This has a knock-on effect of impacting various ecosystems and populations of sensitive species like shark, turtles and birds. There are 4 main fishing methods in operation and I have found a few nice videos that describe each as well as measures that can be used to limit by-catch.

Gill netting: a wall of netting, kilometres long, thankfully banned in many oceans

Long-lining: kilometeres of line with baited hooks are left in the ocean for a few hours

Purse seining: encircling schools of fish (often attracted to a floating device) with a net that is then drawn together

Pole and line: boats carry a number of fisherman with fishing poles who catch fish and hoist them over their heads onto the deck

Each method has it’s drawbacks but for the most part much work is going on to ensure improved catch profiles that limit the by-catch of sensitive species.


In South Africa we add only a small proportion to the global tuna fishing industry but we are a seafood loving nation who is showing an increasing awareness to the issues that surround the ingredients on our plate. I am sure many of you are aware of the WWF and SASSI consumer guide and hopefully you are making your seafood choices based on these recommendations. After my initial surprise at the outcome of our talk being that canned tuna is a sustainable industry, provided the catch methods are fine tuned, we posed some questions to JD regarding a few related issues.

Q: Are any choices or sources of canned tuna better than another?

A: Ideally we want to look out for skipjack tuna, because of the sustainability of this species it appears to be the best choice we can support. Due to the fact that the species is seldom listed on labels if we choose shredded tuna the likelihood is that this will be skipjack.

Q: What are the most sustainable fresh fish (linefish) choices we should be making in South Africa?

A: The best options in South Africa are snoek, yellowtail, albacore (longfin) tuna and yellowfin tuna.

**As a side note – personally I will be eating prawns a lot less, the by catch of these is about 200% compared to tuna averaging around 5-10%. This means for every prawn caught two other non-targeted fish or species of sea life are caught.**

Q: How does the sustainability of local tinned tuna compare to other tinned options like sardines and salmon?

Unfortunately JD is not as involved in these different industries but provided his educated opinion and insight.

A: The local sardine industry is quite well regulated and appears to be quite sustainable. The salmon industry and sustainability question centers around farmed salmon which does have a number of direct and indirect impacts on ecosystems surrounding the farming facilities. Wild stocks are also exploited for the production of feed for these farms but overall farmed fish does relieve some pressure on the wild ecosystems and thus can still be considered a decent option.

For me these are important issues as I often try to increase omega 3 food sources in meal plans and recipes. While tinned tuna is not a great source of this healthy fat tinned salmon and sardines are worthwhile alternatives. Mackerel is another great source of omega 3 although we could not confirm the source of our tinned mackerel and thus evaluate cannot comment on sustainability.  Tinned tuna still remains an economical and viable source of protein and I was comforted to hear that the industry can support the demand while steps are being taken to keep it that way. Work like JD’s is invaluable. If you are interested in a little more you can find some info at International Seafood Sustainability Foundation

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One Response to Into the tuna can – an insight into sustainability

  1. Rupert Feb 23, 2015 at 11:44 am #

    Good to know penz