What Bottom trawling ?
- Bottom trawling is trawling (towing a trawl, which is a fishing net) along the seafloor. It is also referred to as “dragging”.
- The scientific community divides bottom trawling into benthic trawling and demersal trawling.
- Benthic trawling is towing a net at the very bottom of the ocean and demersal trawling is towing a net just above the benthic zone.
- Bottom trawling can be contrasted with midwater trawling (also known as pelagic trawling), where a net is towed higher in the water column. Midwater trawling catches pelagic fish such as anchovies, and mackerel, whereas bottom trawling targets both bottom-living fish (groundfish) and semi-pelagic species such as cod, squid, shrimp, and rockfish.
- Trawling is done by a trawler, which can be a small open boat with only 30 hp (22 kW) or a large factory trawler with 10,000 hp (7,500 kW). Bottom trawling can be carried out by one trawler or by two trawlers fishing cooperatively (pair trawling).
- Global catch from bottom trawling has been estimated at over 30 million tonnes per year, an amount larger than any other fishing method
Impact of Bottom Trawling
- The damage from bottom trawling is not limited to habitat destruction. As the net drags along the seafloor, all creatures in its path—fish, animals, marine mammals, plants, and turtles—are scooped up along the way.
- The fishing vessel keeps the targeted commercial species and discards the remaining, unwanted fish and animals—virtually all of it dead or dying.
- Once coral and sponge communities are destroyed, commercial fish and other species dependent on them for spawning, shelter, nurseries, protection, and food, may also disappear. In addition, overfished species such as rockfish and crab may need corals and other seafloor structures to provide appropriate habitat for recovery.
- By re-suspending bottom sediment, nutrient levels in the ambient water, and the entire chemistry of the water is changed.
- Re-suspended sediment can lower light levels in the water, and reduce photosynthesis in ocean-dwelling plants, the bottom of the food web.
What are the initiatives to prevent bottom trawling in India?
- Recent initiatives taken by the Government of India to end bottom trawling in the Palk Bay area include:
- The launch of a programme on diversification of bottom trawlers into deep-sea fishing vessels for tuna long lining under the Blue Revolution Scheme,
- Construction of harbors like, Mookaiyur and Poompuhar fishing harbors,
- Capacity-building programmes for fishermen of the Palk Bay area in deep sea tuna long lining and
- Fresh registration for bottom trawlers in the Palk Bay area has been banned by the Government of Tamil Nadu.
- India also recently informed that schemes promoting seaweed farming and sea-cage farming have begun in the Palk Bay area to wean away fishermen from deep-sea trawling.