There are nets, and then there are nets.

Herring are increasingly caught in large quantitie susing purse seines,rather than the traditional gill nets. The purse seines concentrate large numbers of fish- of all sizes- to be scooped or pumped out onto carrier vessels. Sardines are small juvenile herring. Until recently, the egg bearing females were sought after and prized for their roe-for the Japanese market. The herring meat,at reporductive stages is of a lower quality and not that long ago was used for bait, animal feed or dumped in landfills, or at sea. A huge waste.Gillneta are smaller scale, and often are used to get bait for the lobster fishery.

Traditionally, groundfish (haddock and cod) were captured by long lines of hooks, or gill-nets (long ago hand lined jigging). Gillnets less frequently used today. Huge and deep towed nets, called trawls, are more frequently used today to catch large amounts of fish-of all sizes and species. They do have regulated mesh sizes, but the meshes get filled up with fish and the trawls capture many size fish. To keep the managers confident that they have a "clean fishery" small or low value species are dumped overboard. If one were to ask anyone who works on a trawler how many fish are dumped overboard, even today-I believe one would get a big surprise.