The scientists concluded that increasingly complex habitat helps young cod survive. They plan to combine these experimental results with data collected in the field to develop computer models that predict the effects of habitat change on the survival of juvenile cod. Down to the Last Fish Until the 1950s, most fisheries caught larger fish such as cod and halibut. As adult fish, these species eat other fish or large invertebrates. This trend towards catching fish with lower trophic levels could greatly impact the sustainability of fish populations.
Smaller fish form the building blocks of the marine ecosystem.
They are the food for the larger fish. They calculated that for each decade since 1950, the average trophic level of fish caught has dropped by about 0.1. The results are worldwide but more visible in the Northern Hemisphere. Even in areas where the fisheries rely mainly on high trophic fish such as pollock, such as the East Bering Sea, the mean trophic level of the catch has been dropping in the last two decades. The authors suggest that fishing down food webs will lead to collapsing food webs.