Most things in life are best done in moderation. Like fishing on coral reefs, for instance. You don’t want to outright ban fishing or people would lose their livelihoods. On the other hand, if you don’t limit the amount of fishing that takes place it would cause irreparable damage to the ecosystem. The problem is, it has never been known in the past how much was too much in terms of fishing a coral reef. A collection of scientists think they’ve come up with the answer to that mystery after doing research on Indian Ocean coral reefs. The magic number seems to be 300 kilos of reef fish per hectare of coral reef. Anything under that amount means a coral reef is in danger.
“Our work shows that as fish biomass – the number and weight of fish living on a reef – declines due to fishing pressure, you cross a succession of thresholds, or tipping points, from which it is increasingly hard to get back,” Dr Nick Graham from the ARC Centre of Excellence for Coral Reef Studies told TerraDaily. “For example, you see patches of weeds replacing coral, you see more sea urchins devouring the coral, you see a general decline in the species richness on the reef, and you see less coral cover. The loss of hard corals is actually the last stage in the collapse of the reef system. Though many people take it as a major warning sign, in fact, by the time you see the loss of live coral cover, it may be already too late to save the reef.”
Under 1000 kilos of fish per hectare and the first warning signs start to show up and, as stated above, under 300 kilos is when the reef is in real trouble. But having this data discovered and publicized is hopefully more than half the battle.
“This information is critical to policy makers and reef managers: if fish stocks can be maintained at a certain level, the chances of retaining a sustainable fishery and a healthy reef system are greatly improved,” Dr Aaron MacNeil from the Australian Institute of Marine Science stated to TerraDaily. “It’s a way of understanding the health of the whole system, not just parts of it. It offers managers a tangible target for protecting both the fishery and the reef, and it supports the need for long-term monitoring of fish in places such as the Great Barrier Reef.”
So now that we know how much is too much, hopefully fishermen will take heed.