It is well known that large fish predators such as many sharks, tuna, swordfish along with cod are fish stocks that are in danger of extinction due to the overfishing pressures.  Many fishery policies were ignorant about the risk to small fish stocks such as anchovies and sardines.  Louis Bergeron writes for University of Stanford this week about the  potential collapse of small fish stocks in "Small fry' fish just as vulnerable to population plunges as sharks or tuna"^[1]

Malin Pinsky, the lead author of the paper cited by Bergeron, began the research to predict the collapse of fish stocks using databases one of which from the Food and Agriculture Organization of the United Nations.  During his research discovered that  "small species were up to twice as likely to have suffered a major decline." Furthermore, Pinsky states

"The important lesson is that all species of fishes can collapse once humans decide to eat or use them, from sardines to swordfish," Pinsky said. "You hear the old adage, 'Don't sweat the small stuff,' but for fisheries, we d have to care about the little guys. This really contrasts with what scientists, managers and the conservation community have often assumed up until now."

The smaller the fish, the more rapid the fish reproduce so population crashes were thought to be less likely for these small species.  As larger fish reproduce at older ages and take longer to reach reproductive age, these species are clearly at risk to heavy fishing predation by humans.  It is certainly evident that small fish are lower on the food chain in the ocean and so if these stocks crash, all the higher trophic levels will be impacted. 

Students could construct food chains of ocean communities from internet research to illustrate the dependence of higher trophic levels on releatively few speices albeit in very large populations.