Presentation on theme: "Freshwater fish research and conservation in the Addo Elephant National Park Olaf Weyl et al. Department of Ichthyology and Fisheries Science, Rhodes University,"— Presentation transcript:
Freshwater fish research and conservation in the Addo Elephant National Park Olaf Weyl et al. Department of Ichthyology and Fisheries Science, Rhodes University, South Africa
Graham Traas (MSc) Henning Winker (PhD)Bruce Ellender (MSc)Mpho Ramoejane (MSc)Phillip Weyl (Hons) Olaf Weyl (PI) Ernst Swartz (SAIAB) Tony Booth (RU)Anton Bok (Fishways) Jim Cambray (Albany Museum)Tim Andrew (EFA)
Addo Elephant National Park Proclaimed in 1931 360 000 ha mega-park. 120 000 ha marine reserve.
AENP-Goals Conserve a representative sample of Eastern Cape ecological patterns and processes. Manage the park to ensure the long term persistence of biodiversity Reduce external pressures (inappropriate land use, illegal resource use, impacts of invasion of alien biota)
Addo Elephant NP Includes 5 of South Africa's 7 biomes. One of the densest African elephant populations on earth. Unique flightless dung beetle. Incorporates the largest coastal dune field in the southern hemisphere. Big Seven, (elephant, rhino, lion, buffalo, leopard, southern right whale and great white shark). Protects the world's largest Cape gannet breeding population on Bird Island.
Freshwater fish < 5% of South Africa’s rivers fall within protected areas (Abell et. al., 2007) SAN-Parks funded research: Fish distribution and abundance. Determining critical conservation areas Not the global norm and exemplifies South African recognition of freshwater fish as conservation priorities.
East Cape redfin Pseudobarbus afer IUCN listed (Endangered) Restricted to tributaries in upper catchment areas. Preliminary results suggest that maternal gene flow among populations is not uniform.
Goldie barb Barbus pallidus Addo Elephant NP populations are likely to be distinct from the inland populations. Restricted to tributaries in upper catchment areas. Widespread but not abundant photo Roger Bills
Chubbyhead barb Barbus anoplus Recorded from one locality in Addo. Mainstream species only sampled in one locality. Reasons for decline unknown but likely to include competition with and predation by alien species. photo Roger Bills
Moggel Labeo umbratus Widespread includes Orange River & east flowing drainage. Widespread in Addo Elephant NP. Mainstream species and sampled in Sundays River & Wit tributary.
Other natives Gobies and Anguillids are widespread in the park.
Indigenous species Upper catchments of tributaries are key conservation areas Maintaining important catchment processes and flow regimes in these areas is vital.
The Orange River Transfer of Orange River water for irrigation since mid 1970’s Transformed the Sundays River from a seasonal to a perennial river. Flows governed by irrigation demands.
Other imports of unknown source Common carp Largemouth bass Mosquitofish
Alien invasive fish Invasion is a downstream process Upstream invasion impeded by barriers.
Effects Evidence of Labeo umbratus X Labeo capensis hybrids. C. gariepinus are very abundant in the Sundays system. –80 anglers x 2 days fishing = 15 tons –100 kg per angler/day. –Impact not quantified but small barbs are now absent from Sundays mainstream and Darlington Dam.
The Wit River (field trip site) Good example Typical upper catchment stream. Slagboom Dam has excluded Orange River fish. Important site for L. umbratus to avoid hybridisation. Dam was stocked with largemouth bass M. salmoides by anglers. These have also invaded the river.
Invertebrates study site Phil Weyl (Entomology student) Sample site with bass Sample site with no bass Slagboom dam
2 biotopes sampled Stones in current marginal vegetation/calm pools
All invertebrates were sorted and identified to family
Dendrogram of the cluster analysis Stones in current: Largemouth bass present and absent Marginal vegetation: Largemouth bass present Marginal vegetation: Largemouth bass absent
P. afer density P. afer density fish·m 2 UpstreamDownstream Relative Fish abundance 3-pass depletion electrofishing in pools < 70cm deep Sampling site
Other threats Water abstraction & alien vegetation. Connectivity between habitats altered. Predators especially effective when river flow is low. Genetic differences between P. afer populations suggests that if we loose one population we cannot replace it. Little understanding of competition between indigenous and alien species.
Take home messages Main river is altered habitat and source of invasion. Indigenous fish are threatened by alien invasive fishes through predation, competition & hybridization. Upper catchments of tributaries as key conservation areas –Maintaining important catchment processes and flow regimes in these areas is vital (e.g. alien vegetation removal). –Stopping upstream invasion by alien invasive fish is probably more important than ensuring upstream migration of indigenous species.
The field trip 07:00 Departure from Grahamstown. 09:00 Meet me at Slagboom Dam Walk/drive to various sites on the river and meet some of its inhabitants. I will show you various sites and point out interesting features mentioned in the talk as we walk up the system. Lunch somewhere along the river. 14:00 Addo main camp to see elephant, warthogs, zebra and other mamals.
Things to remember Wear walking shoes the terrain is uneven. Bring binoculars if you have. Bring sunscreen, hat & a warm jacket (you now know the Eastern Cape weather). Do not try to touch or attempt to feed any animals. Look out for snakes. Don’t collect any fish, we will be in a conservation area and the fish populations are threatened. If you are unsure of anything, please ask.
Thank You! Olaf Weyl, Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown 6139,South Africa. firstname.lastname@example.org