Impact of maximum sustainable yield on mutualistic communities

We analyze effects of reaching the maximum sustainable yield (MSY) in a system of n cooperating logistic populations under proportional harvesting strategy. In case a selective harvesting effort adjusted to each species is implemented, the optimum effort is smaller than half the biotic potential of each species. This results in the total maximum sustainable yield (TMSY1) which does not affect the persistence of the system. In case the system is harvested with a common harvesting effort which is approximately the same for all cooperating species, like in a trawler fishing, the optimum harvesting effort leads to the TMSY2, where TMSY1 ≥ TMSY2. In addition, species with lower biotic potential and carrying capacity may be driven to extinction, especially if these species weakly cooperate with the rest of the system. Hence, a call for implementation of TMSY2 may be equivalent to a call for extermination of some species, and it runs against the Convention on Biological Diversity (CBD, 1992). Since the documents advocating MSY, starting with the Johannesburg Implementation plan (IP, 2002) and including the EU Green Paper (EU, 2009), use TMSY2, the call for MSY must be urgently retracted and replaced with a call for adaptive management that respects CBD.

► Species specific optimum harvesting effort will not cause species extinction.
► Common optimum harvesting effort, like in trawling, may cause species extinction if cooperation is low.
► Species with lowest biotic potential or carrying capacity are most susceptible to extinction.
► In obligatory mutualistic systems, harvesting to reach TMSY will not cause species extinction.