Huge new stock available to overfish and deplete

I’m fascinated and confused by this new study reported on phys.org about mesopelagic fish (the mesopelagic zone is the area 200-1000 m/650-3300 ft below the surface of the ocean). These are the fascinating bits:

1. The mesopelagic fish biomass is at least 10 times greater than previously thought.
2. 95% of world’s fish live in mesopelagic zone.
3. The mesopelagic fish genus Cyclothone sp. is probably the most abundant vertebrate on earth.
4. Mesopelagic fish can detect nets from a distance of 5 meters.
5. Because of their net-detecting abilities, and because mesopelagic fish are for the most part not commercially harvested, we appear to have left a vast stock of fish that is largely untouched.
6. Our knowledge of oceans is limited at best – as well as our knowledge of how climate change affects and is affected by marine ecosystems.

Here’s the confusing part. It’s hard to tell for sure, but the article appears to promote some kind of pro-industry, pro-waste agenda, and includes oddly positive quotes by the researchers:

This very large stock of fish…is untouched by fishers. They can’t harvest them with nets. (phys.org)

I’m not sure how this can be true for all mesopelagic fish. Commercial lanternfish fisheries already exist in limited numbers, and commercial deep-trawl fisheries have abused deep waters for years. (See Deep-sea fish in deep trouble: Scientists find nearly all deep-sea fisheries unsustainable for more information about the problems with deep sea fishing.)

An image of an enormous sunfish is used to illustrate the news, which from the comments apparently gives some readers the impression that we can replace our decimated epipelagic stocks (bluefin tuna, for example) with new mesopelagic species. One reader on phys.org asks: I wonder if these fish are edible and delicious?

Sunfish look like this:

Sunfish. Image: Wikipedia.

The Wikipedia page on sunfish includes an image of a 1600 kg (3500 lb) sunfish caught in 1910, and a plate of prepared sunfish served with broccoli. (Sunfish even like to lie horizontally on the water’s surface, as if preparing themselves for our cooking grills.) In contrast, most mesopelagic fish are small filter feeders, like the bioluminescent lanternfish that account for as much as 65% of all deep sea fish biomass:

Lanternfish. Image: Wikimedia.

This may not be as appetizing to that phys.org reader. And no matter how many fish we have left, the health of oceans is still dire:

Results from the latest International Programme on the State of the Ocean (IPSO)/IUCN review of science on anthropogenic stressors on the ocean go beyond the conclusion reached last week by the UN climate change panel the IPCC that the ocean is absorbing much of the warming and unprecedented levels of carbon dioxide and warn that the cumulative impact of this with other ocean stressors is far graver than previous estimates. (IPSO)

The good news is that our oceans may be healthier than we realized, and we may have more fish than we believed. The bad news is everything else. We still have too little understanding about how our oceans work, and we’re pushing the enormous, collective resources of our oceans to their absolute limits. Here’s hoping that the information from this study is used to better understand and protect our ocean resources, and not promote further fishing down the food web. We need a Montreal Protocol for fisheries.

Read more: Large mesopelagic fishes biomass and trophic efficiency in the open ocean and Ninety-five per cent of world’s fish hide in mesopelagic zone.