Sustainable Seafood: Part 3 - How does sustainability relate to seafood?

Part 3 in a series of posts about sustainable seafood.
Part 1 - This is the post that started me thinking about the problem.
Part 2 - Sustainable Seafood: Part 2 - What is sustainability?

Sustainable Seafood: Part 3 - How does sustainability relate to seafood?
From MarineBio:

"Fish currently supply the greatest percentage of the world's protein consumed by humans. This fact may soon change, however, given that most of the world's major fisheries are being fished at levels above their maximum sustainable yield and many regions are severely overfished. More than 70% of the world's fisheries are overexploited, which threatens the health, economy, and livelihoods of communities all over the world."

The MarineBio website lists a number of issues that need to be addressed quickly in order to preserve fish stocks as a natural resource. Each of these issues is an example of unsustainable practices in the seafood industry. The issues include:

1. Overfishing;
2. Inadequate conservation and management practices;
3. Habitat loss as a result of harmful fishing practices; and
4. Government subsidies.

Each of these issues describes a different insult to the idea of sustainable fishing. Any one of these issues in isolation would be a cause for concern and a good reason to act to protect fish stocks. In many cases it is not just one of these issues that is affecting fish stocks however, but some combination of two or three or all of these issues working in parallel to meet the needs of the present while compromising the ability of future generations to meet their own needs.

Overfishing
Overfishing can be defined in a number of ways. However, everything comes down to one simple point: Taking more fish than the system can afford to give up leads to an overall degradation of the system.

From a biological perspective overfishing occurs when fishing mortality has reached a level where the stock biomass has negative growth. Fish are being taken out of the water so quickly that the replenishment of stock by breeding slows down. If replenishment and immigration are insufficient to cover losses due to mortality and emigration then the population must decrease. As the population decreases, fishing has an increasingly significant effect on the remaining population. If fishing pressure does not decrease to allow replenishment to outstrip (or at least equal) mortality, then a fish population can crash to a point where replenishment is no longer possible. The ability of populations to recover also depends on whether the conditions of the ecosystems are suitable for population growth. Dramatic changes in species composition may establish equilibrium energy flows that involve other species compositions than had been present before (ecosystem shift).

Inadequate conservation and management practices
For generations we have believed the ocean to be pretty robust - probably because it is vast and under-explored; however, it is becoming increasingly obvious that ocean resources are finite, and depletion of these resources beyond sustainable levels is often irreversible. Overfishing not only causes depletion in individual fish stocks, but also disruption to entire ecosystems and food webs in the ocean. It is necessary to manage fisheries at the ecosystem level if we want to ensure the sustainability of fish stocks. This can be done by:

1. Maintaining populations of target species at levels that allow them to fulfill their natural role in ecosystems and enable positive (greater than mortality) rates of reproduction;
2. Eliminating the use of fishing gear that creates a high level of bycatch, or the incidental catch of nontarget species; and
3. Closing feeding, breeding and spawning grounds to fishing to protect marine ecosystems from exploitation at these sensitive times in their lifecycles.

Habitat loss as a result of harmful fishing practices
Eliminating destructive fishing practices is an essential step to bring sustainability to the seafood industry. Bottom trawling destroys habitats, indiscriminate fishing practices such as drift netting and long-lining are destructive to habitats and non-targeted species and lost or discarded fishing gear is also destructive to underwater habitats and ecosystems.

Deep-sea trawling is particularly harmful to ecosystems because it indiscriminately bulldozes or entangles many benthic species. Continued destruction of deep-sea areas is causing species to become extinct before they are even observed, let alone identified, by science. From SeaWeb:

"In a few hours, the massive nets that drag the bottom and weigh up to 15 tons, can destroy deep-sea corals and sponge beds that have taken centuries or millennia to grow. The trawlers target fish such orange roughy and grenadiers for food, and sharks for the cosmetic industry. These fish are generally long-lived, slow growing and late maturing so their populations take decades, even centuries to recover."

Government subsidies
To catch around $70 billion worth of fish per year, the commercial seafood industry spends approximately $90 billion per year and incurs total costs of over $120 billion per year. A multitude of government subsidies make up the difference between their income and expenditure. The practice of providing governmental support to the fishery sector is widespread among major fishing nations. While precise data are difficult to obtain, the basic facts are not considered controversial. Governments around the world are providing tens of billions of dollars in subsidies annually to the fishery sector, for a wide variety of purposes, and in many different forms. While smaller in absolute amount terms than, for example, subsidies to the agricultural sector, these payments are conservatively estimated to be roughly 20-25 per cent of the annual revenues of the commercial fishing industry.

Subsidized incentives make it easy for the seafood industry to build more fishing power than fish populations can support. There is now a mismatch between what the ocean can make and what the seafood industry can take, meaning that the seafood industry is currently meeting the needs of the present while compromising the ability of future generations to meet their own needs.

Next:
Sustainable Seafood: Part 4 - Can sustainable seafood guides help protect the environment?