A holistic and scientific basis for achieving ecosystem-based management is needed to counter the continuing degradation of coral reefs. A holistic basis for sustainability is developed that includes information on reported and modeled yields, biomass and ecosystem thresholds, biomass recovery rates, and changes in yield over time. The coral reef fisheries literature reports high variability but this aligns well with high variation reported for biomass recovery and associated logistic model yield predictions. Recovery rate variability can, however, be attributed to a number of factors other than variation in endogenous production, including poor compliance and movement of fish into closures. Nevertheless, high harvest rate variation is more likely due to both temporary and long term harvesting beyond sustainable levels. For a conservative stock of 0.50 pristine biomass (~50 tons/km2), the most controlled recovery studies predicted mean yields of 7 tons/km2/y but high variability ranging from 2 to 13 tons/km2/y. There are few studies of reef fisheries yields over time but Kenyan fisheries studied for >10 years indicate that yields of > 6.9 tons/km2/y were not sustainable. Fish production at low biomass can increase and offset predicted declines in yields but biomass studies in Kenya found a small increase that would be insufficient to avoid declining yields. Ecological change occurs prior to the logistic model's maximum yield predictions, with 3 of 8 abrupt changes occurring before MSY. Knowing fishable biomass is important when predicting sustainable yields and a variety of metrics suggest that it should be maintained above 50 tons/km2 to avoid unsustainable yields.



McClanahan, T. R., Wildlife Conservation Society, Kenya, tmcclanahan@wcs.org


Oral presentation

Session #:21
Date: 06/23/2016
Time: 14:00
Location: 310 THEATER

Presentation is given by student: No