There are various types of bottom trawling and the type used depends on what you're targetting and the size of the catch. The vessels I mostly worked on in the Falklands were factory ship bottom trawlers, averaging at around 40-50 tonnes per catch, 3-4 catches per day. They'd stay out for months at a time, coming in to dock only to change crews, offload fish and take on fresh supplies. One time we refuelled at sea which was pretty fun to watch. The vessels would go after squid during the two squid seasons and then switch to demersal fish the rest of the year. The gear looked identical from what I could tell, regardless of target species. The net would skim the sea bed behind two trawl doors. The top of the net would have buoys to help keep it open and sometimes the net would have fringes on the bottom which I assumed was to try and agitate the sea bed and prevent a barrier to fish trying to swim under.
From what little I've seen of the UK fishing fleet it seems to mostly operate using more small vessels doing day-trips. Their trawls are smaller but that doesn't necessarily make them less destructive. Flatfish living in the sediment have to be scared out and that requires greater contact with the sea bed.
For shellfish such as scallops, dredging is used which is even more destructive than bottom trawling.
Personally I'd ban all fishing that comes into contact with the sea bed. It would mean the loss of some fisheries but I don't think we can justify the destruction any longer.
Bird on a Fire wrote: ↑
Tue Mar 02, 2021 6:02 pm
Marine Stewardship Council certification is better than nothing but AIUI there are some fairly big flaws. Simply not eating stuff is a better solution
I was really supportive of the MSC but the more I hear about it the more dubious I get. It's mostly gossip I've heard at conferences and workshops so I have no idea about the validity of the criticism.
* I worked on one massive pelagic trawler that was almost 100m long and had 60-80 tonne catches which was an incredible experience, until the monotony set in which it did very rapidly. Despite the huge catches 95% was one target species, 94.95% was another target species and I'd be lucky if I got a couple of buckets of bycatch. The main target species also showed sexual dimorphism with the females being larger than males, and they were all spawning, so I could tell just by looking at them their sex and maturity without needing to cut them open (I always did, just in case). I could get biological data for 100 fish in less than an hour. 30 minutes for data entry and then I had 22 1/2 hrs to kill until the next shift.