Coral reef fish communities, diversity, and their fisheries and biodiversity status in East Africa

Abstract

Coral reef fish along the East African coast were evaluated for the distinctiveness of their communities, their distributions and interactions with the environment, and their responses to management. I studied the biomass and species richness of 24 fish families at 238 unique sites in Kenya, Tanzania, and Mozambique. I identified an unfished benchmark that was associated with high biomass, high-compliance closures or low access to fishing along with 6 additional statistically different communities. In the benchmark community, biomass was dominated by snappers, surgeonfish, parrotfish, and wrasses. Of the 24 families studied, 11 declined relative to the benchmark community, with the greatest declines observed among surgeonfish, snappers, sweetlips (grunts), groupers, and triggerfish. I evaluated the community's spatial distributions and associations of 15 of 23 environmental and human-impact variables. Fish biomass was most positively influenced by the extent of shallow water < 50 m adjacent to the sites, depth, and high-compliance closures and negatively impacted by human populations within a 100 km radius of the site. Number of fish species was largely predicted by biomass with weak evidence for local environmental control. Classification of the biomass into 3 proposed management thresholds revealed that ~38% of the sites were below sustainable yields, 54% were below maximum species richness, and 92% below a proposed stable-ecosystem or conservation threshold. Therefore, increasing biomass of vulnerable taxa through fishing restrictions is recommended for maintaining sustainable fisheries, species diversity, and ecosystem services.

The great stagnation and environmental sustainability: A multidimensional perspective

“…With regard to fish stocks, the negative impact at global level is significant (−8.1%), but again the result is only statistically significant in the African continent (−8.06%). This is in line with recent reports and evidence on the significant deterioration of fish stocks in Africa (e.g., BBC, 2018; Hilborn et al, 2020; McClanahan, 2019; Mcclanahan et al, 2019). Furthermore, marine protected areas do not necessarily reduce fishing pressures (Agardy, di Sciara, & Christie, 2011; Bates et al, 2019), especially if only a small percentage of oceans is protected (Dasgupta, 2018).…”

COVID-19 impacts on coastal communities in Kenya

“…Our interviews revealed some increased fishing pressure on inshore fishing grounds in three communities, likely due to labour from the informal economy being attracted to the fishery as a result of COVID restrictions. However, this increased effort did not reportedly result in increased yield, likely since the Kenya fishery is already heavily overexploited ( McClanahan, 2019 ). Indeed, in line with our findings, preliminary evidence suggests conflicting reports on whether the COVID-19 pandemic has increased or decreased pressure on inland lake fisheries in East Africa ( Aura et al, 2020 , Stokes et al, 2020 ).…”

Decadal shifts in traits of reef fish communities in marine reserves

“…TSAs were included in the models as they were associated with coral bleaching events. Moreover, McClanahan 38 showed that variation in TSA is associated with the biomass of certain fish families. Fish communities were expected to exhibit a lagged response to disturbances such as thermal stress 14 .…”