Editing Atlantic cod (section)

===Predation===
Atlantic cod are apex predators in the Baltic and adults are generally free from the concerns of [[predation]].<ref name=":0">{{cite journal|last=Steneck|first=R. S.|title=Apex predators and trophic cascades in large marine ecosystems: Learning from serendipity|journal=Proceedings of the National Academy of Sciences|date=14 May 2012|volume=109|issue=21|pages=7953–7954|doi=10.1073/pnas.1205591109|pmid=22586126|pmc=3361373|bibcode=2012PNAS..109.7953S|doi-access=free}}</ref> Juvenile cod, however, may serve as prey for adult cod, which sometimes practice [[Cannibalism (zoology)|cannibalism]]. Juvenile cod make substrate decisions based on risk of predation. Substrates refer to different feeding and swimming environments. Without apparent risk of predation, juvenile cod demonstrated a preference for finer-grained substrates such as sand and gravel-pebble. However, in the presence of a predator, they preferred to seek safety in the space available between stones of a cobble substrate. Selection of cobble significantly reduces the risk of predation. Without access to cobble, the juvenile cod simply tries to escape a predator by fleeing.

Additionally, juvenile Atlantic cod vary their behaviour according to the foraging behaviour of predators. In the vicinity of a passive predator, cod behaviour changes very little. The juveniles prefer finer-grained substrates and otherwise avoid the safer kelp, steering clear of the predator. In contrast, in the presence of an actively foraging predator, juveniles are highly avoidant and hide in cobble or in kelp if cobble is unavailable.<ref name=Gotceitas>{{cite journal|last=Gotceitas|first=V|author2=S. Fraser |author3=J.A. Brown|title=Habitat use by juvenile Atlantic cod (Gadus morhua) in the presence of an actively foraging and non-foraging predator|journal=Marine Biology|year=1995|volume=123 | issue = 3|pages=421–430|doi=10.1007/bf00349220|bibcode=1995MarBi.123..421G|s2cid=84470358}}</ref>

Heavy fishing of cod in the 1990s and the collapse of American and [[Canadian cod]] stocks resulted in [[trophic cascade]]s. As cod are [[apex predator]]s, [[overfishing]] them removed a significant predatory pressure on other Atlantic fish and crustacean species. Population-limiting effects on several species including [[American lobster]]s, [[crab]]s, and [[shrimp]] from cod predation have decreased significantly, and the abundance of these species and their increasing range serve as evidence of the Atlantic cod's role as a major predator rather than prey.<ref name=":0" />