Chapter 15

Many Web sites that advise consumers on the fish species that they should eat (because they are harvested in a sustainable manner) recommend against buying orange roughy (Hoplostethus atlanticus ). Hilborn et al. (2006) challenged this interpretation and showed that orange roughy were being harvested very near to maximum sustained yield and were not being overfished. Discuss this controversy and explain the principles you would use to define a stock that was overharvested.

Fish communities consist of many different species, only a few of which are typically the focus of commercial or recreational fishing, One way to manage such fisheries is to use standard criteria for maximum sustained yield on the single species of interest, and to ignore the other species in the community. Discuss how this simplified approach might have disastrous consequences for the other species in the ecosystem. Walters et al. (2005) discuss this issue.

Examine the catch statistics for a fishery in your area or in an area of interest to you. Sources of data on the Web might be the Fisheries Statistics of the United States, Fisheries Statistics of Canada, or the Food and Agricultural Organization's Web site. If the fishery you choose has been managed, is there any evidence of overfishing?

One of the assumptions of maximum sustained yield models is that birth, death, and growth responses to population density are repeatable, such that a given population density will always be characterized by the same vital statistics. What mechanisms may make this assumption false?

The Peruvian anchovy fishery (Figure 4 ) is still among the largest fisheries in the world. What happens to this large biomass of fish once it is caught?

Ludwig and Walters (1985) showed in a computer simulation that the management of a hypothetical fishery could be done better using simple yield models like the logistic equation than by using more realistic, detailed models like dynamic pool models. Discuss why this might be correct for a real fishery.