Skip to content

Conservation

Pacific conservation measures for bigeye tuna are urgently needed

by Dave Armstrong 12 Oct 2012
Pacific conservation measures for bigeye tuna are urgently needed

Spatial fit to observed and predicted big-eye tuna (BET) catch for all fisheries. The area of circles is proportional to the total observed catch. (the reds approach 100% or 1.0) An eastern distribution can already be seen, and is predicted to become even more pronounced; Credit: © Credit: PNAS

The magnificent graph of the greatest ocean belies the truth. The variety of fishing techniques used in the Pacific means that BET (big-eye tuna) biomass is soon going to dip below the maximum sustainable yield levels. Despite a purse seine net ban on the high seas, this second-largest of the tuna species has continued to decline.

Longline fishing needs to be banned quickly in the spawning areas in order for the efficient conservation of breeding fish. It will now be 2030 before we can see any benefits, even if the necessary measures are taken. Other species of tuna are obviously affected, as they are often caught together.

The large yellow-fin tuna are involved, but skipjack and BET tuna are also heavily fished in the purse-seine fishery for canning here, at the relatively low cost of $2 per kg.

Since the '60s, longline fishing has been used to drastic effect to haul in the $10.2 per kilo BET tuna. Note that price differential! These fish however make up less than 50% of the their total catch. The smaller skipjack tuna is mainly caught by purse seine fishing and consigned to our supermarket cans, while this largest world fishery was also trapping juvenile BET.

yellowfin tuna

This yellowfin tuna is among those species caught in Pacific fisheries, as the bigeye (here called the BET) joins the ranks of heavily-threatened tuna species - Yellowfin tuna; Credit: © Shutterstock

While the skipjack survives, the BET population has suffered more. In predictive models, the BET biomass built up for 15 years before 1995, after fishing was stopped. Environmental factors linked possibly to global warming then reduced the BET populations and fishing now limits increases and causes pronounced decreases in a fluctuating model graph. The model mainly concentrates on the history of BET in an effort to predict its situation today and not to forecast the future.

The results are illuminating. Banning fishing in an area causes little increase in BET biomass. The fish can be caught elsewhere, especially as the fishing fleets seem to concentrate their efforts on areas right next to the banned areas. Longline fishing, designed to catch mature fish, is death to the spawning areas. Prohibition is obviously a first step to recovering this important population.

Changes in the distribution of adult bigeye tuna

Changes in the distribution of adult bigeye tuna (BET) density in the Pacific Ocean under four different scenarios at the end of a simulation of conditions from 1980---–2003. CE, areas closed to purse seiners and loss of fishing effort; CEL, areas closed to purse seiners and loss of fishing effort with additional closure of an area to LL fishing; F2S, with no closure but FADs use prohibited and FAD effort displaced to free schools; F2SL, same as F2S but with additional closure of an area to LL fishing. The colour background gives the density ; Credit: © PNAS

Benefits of closures for the local fishermen could be an incentive to go ahead with their implementation, but for the fish, the benefit is limited. A 15-year period (ie. the animal's life-span) is required to re-build the stock. The changing climate is highly likely to require a much longer period for the species, which is expected to shift eastward in its distribution, because of oceanic warming.

Perhaps a Pacific fishing network would allow certain kinds of fishing in specific zones. Relevant local development programmes would permit economic progress while conservation would mean preservation of those developing economies. The high price of tuna has now caused extinction threats to most of the species, despite their previous huge populations. Disaster has struck too often with tuna and to be honest, most other commercial fishing scenarios.

It's about time the vastness of the Pacific allowed some species to provide a living for humans and yet survive in suitable conditions themselves. John Sibert of the University of Minnesota, and his colleagues have provided this most valuable contribution towards efforts to stabilise the tragic loss of species, human livelihoods and whole environments. They publish in the US journal, PNAS (Proceedings of the National Academy of Sciences).


Trending Eco-Friendly Clothing

Love My Planet Women's Relaxed Fit Hoodie
Earth
Quick Add
Close
Notify me
Notify me
Love My Planet Women's Relaxed Fit Hoodie
Love My Planet women's eco-friendly relaxed fit hoodieSize Guide Centimeters 8 10 12 14 16 18 Bust 84 88 92 97 103 108 Waist 66 70 75 80 85 91 Hips 91 95 99 104 109 116 Bust: Measure around the fullest part of...
£38.00
£38.00
Close
Notify me
Notify me
Penguins Hate Push-Ups Men's Pullover Hoodie
Earth
Quick Add
Close
Notify me
Notify me
Penguins Hate Push-Ups Men's Pullover Hoodie
Penguins Hate Push-Ups men's eco-friendly pullover HoodieSize Guide Centimeters XS S M L XL XXL Height 171 175 179 183 189 195 Chest 86 93 99 104 116 129 Waist 71 76 81 89 99 112 Chest: Measure all round your chest just below...
£38.00
£38.00
Close
Notify me
Notify me
Lightning Bolt Kids Long Sleeve T-Shirt
Earth
Quick Add
Close
Notify me
Notify me
Notify me
Lightning Bolt Kids Long Sleeve T-Shirt
Lightning Bolt kids eco-friendly long sleeve t-shirtSize Guide Centimeters 3-4yrs 5-6yrs 7-8yrs 9-10yrs 11-12yrs Height 98 112 125 136 147 Chest 60 66 70 75 84 Chest: Measure all around your chest just below your armpits. Height: Your natural height If you fall between...
£18.00
£18.00
Close
Notify me
Notify me
Notify me
Union Jack Tote Bag
Earth
Quick Add
Close
Notify me
Notify me
Union Jack Tote Bag
Union Jack eco-friendly colour tote bagProduct Specification Organic Cotton Tote Bag. Twill Weave (170gsm). 37 x 42 cm (7cm gusset.) Made in India / Designed on the Isle of Wight. Wash Cool, Hang Dry.
£16.00
£16.00
Close
Notify me
Notify me
Prev Post
Next Post

Eco-Friendly Shop

Women's Clothing

Eco-Friendly Clothing for Women Our online shop offers a wide range of sustainable women’s clothing products, including t-shirts, hoodies, vests, sweaters, shorts, and...
Shop Now

Men's Clothing

Eco-Friendly Clothing for Men Our online shop offers a wide range of sustainable men’s clothing products, including t-shirts, hoodies, vests, sweaters, shorts, and...
Shop Now

Kids Clothing

Eco-Friendly Clothes for Kids Our online shop offers a wide range of sustainable kids clothing products, including t-shirts, hoodies and jumpers. Our garments...
Shop Now
Someone recently bought a
[time] ago, from [location]

Thanks for subscribing!

This email has been registered!

Shop the look

Choose Options

Earth Times
Sign up for exclusive updates, new arrivals & insider only discounts

Recently Viewed

Edit Option
Back In Stock Notification
this is just a warning
Login
Shopping Cart
0 items

Before you leave...

Take 20% off your first order

20% off

Enter the code below at checkout to get 20% off your first order

CODESALE20

Continue Shopping