Old fishes play a crucial role in increasing population of the fishes. But recently it has been found that the number of old fish is gradually decreasing due to excessive fishing. The longer a fish lives, the more it can reproduce.
A UW postdoctoral researcher at the School of Aquatic and Fishery Sciences, Lewis Barnett said: “From our perspective, having a broad age structure provides more chances at getting that right combination of when and where to reproduce.” If we notice in forestry, giant, old trees help to grow and support the ecosystem by providing shelter to many animals and plants. For this reason, reduction in their number is an alarming issue. It is the same for the old fish.
According to Barnett “More age complexity among species can contribute to the overall stability of a community. If you trim away that diversity, you’re probably reducing the marine food web’s ability to buffer against change.” At which age a fish is considered old varies. While some fish can live up to 200 years, others may not even go past 10. The marine environment keeps changing. Suitable conditions for eggs to hatch and fish to grow are not always available. An older fish gets more chances at laying eggs, thus increasing the chance for success over time.
Co-author Trevor Branch considers old fish as an insurance policy, as they increase the chance of fish population growth. A fish undergoes a lot of changes as it ages. They change their food habit and thus can eventually become a more dominant predator in the food web. If you take them out, the diversity and stability is greatly hampered.
Big and older fish are different than the rest. And that is why co-author Tim Essington thinks they act as a hedge against risk.
In an analysis done on 63 populations living in 5 ocean regions worldwide, researchers found that the number of old fishes has decreased 79 to 97 percent. The main reason of this problem is fishing pressure. The longer a fish lives, the longer it has chances of getting caught. The factors like disease and pollution might also be responsible.
Researchers suggest some solutions to this problem. Fishing should be limited to fishes below and above a certain size and age, protecting the new and old fish. Some areas can be restricted and fishing would not be allowed in those areas. And fishing zones can be rotated, allowing to fish to grow properly.