Study

The effect of marine reserves and habitat on populations of East African coral reef fishes

  • Published source details McClanahan T.R. & Arthur R. (2001) The effect of marine reserves and habitat on populations of East African coral reef fishes. Ecological Applications, 11, 559-569.

Summary

The effect of fishing, the duration of protection from fishing, features of reef habitat, including benthic cover and sea urchin abundance, and the distance between reefs, were examined to determine the ability of these factors to predict ecological aspects of fish communities for conservation purposes and their implications for habitat management.

Study sites: Along a 400 km stretch the East African coastline 22 sites were studied, 13 in Kenya and 9 in Tanzania (see Figure 1).

Categorisation of reefs was based on the following questions:

Effects of fishing pressure on reef communities?
1. More than 25 years of protection from fishing
2. Smaller & recently protected reefs that had excluded fishing for less than 10 years
3. Tanzanian and Kenyan unprotected reefs

Effects of reef morphology on community composition?
1. Fringing sites protected
2. Fringing sites unprotected
3. Patching sites protected
4. Patching sites unprotected

Algal and hard coral organisms >3 cm were categorised into:
1. Algal turf
2. Fleshy algae
3. Coralline algae
4. Calcareous algae
5. Sponge
6. Sand
7. Sea grass
8. soft coral
9. Hard coral

127 fish species within 8 common coral reef fish families were sampled:
1. Surgeonfishes (Acanthuridae)
2. Triggerfishes (Balistidae)
3. Butterflyfishes (Chaetodontidae)
4. Pufferfishes (Diodontidae)
5. Wrasses (Labridae)
6. Angelfishes (Pomacanthidae)
7. Damselfishes (Pomacentridae)
8. Parrotfishes (Scaridae)

Habitat variables were often significantly associated with fish community variables in fringing reefs, but not in patch reefs. Fish diversity was positively correlated with hard coral and coralline algal cover, and negatively correlated with sea urchin and algal turf abundance. However, analysis suggests that protection from fishing was the single most important factor affecting fish abundance and diversity. Consequently, many of the habitat correlations were probably due to direct and indirect effects of fishing on reef ecology, where heavy fishing results in increases in sea urchin and algal turf abundance and reduces hard coral and coralline algal abundance.

Protected areas had higher abundances and species richness of commercially important triggerfish, surgeonfish and parrotfish compared with nearby unprotected areas. Older reserves had more and rarer species than young reserves or fished reefs and, consequently, the maintenance of reserves older than 10 years may be needed to sustain the full local diversity of fishes.


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