First question does the by catch system work
I believe Yes
commercial traget certain species at certain times of the year and in various locations useing aquired knoledge and historical data Due to the vast spread of species on the sea bed there will always be by catch these bys are limited to a max percentage of total catch so why dump godd fish
Second question Should commercials return undersize fish again Yes
For certain species undersize fish have no commercial value or not enough to justify the fuel and running cost of catching In fact some times legal sized fish have in sufficent value and are avoided (bass being one but not the only exception) The answer to under size fish is fishing gear and method square mesh pannels in trawls do work but more needs to be done on this the increase in mesh size for tangle nets has had a marked effect on landings of small fish (Having done quite a bit of wreck netting in the past i have seen the evidence my self. with a mesh of 6" or more the 2 to 3 lb codling and pollock just dont show. and old style 4.5" mesh fished same day same place had plenty of small fish.) ( In Iceland if a gill netter of similar encounter a run of samll fish, the authorities close the area to all fishing)
Third question Max sustainable yield Again Yes
A great idea the only problem is the science is always vague, none existant or contradictory
A fourth idea might just be a closed season on all species. As sea anglers we all know that the cod gather for spawning in the late winter and early spring how about a closure from Feb to May? I believse sand eels spawn in Jan and Feb but in different places so we could give the base of the food chain a rest then Its done for all of our river fish including the Salmonids.
Any other ideas apart from burn the trawlers and hang the crews