Aaron P. Jenkins, Wetlands International Oceania Chair IUCN/WI Freshwater Fish Specialist Group

Transcription

1 Impacts of tilapia on indigenous fishes & ecological processes on oceanic islands: lessons from Fiji & the Pacific Aaron P. Jenkins, Wetlands International Oceania Chair IUCN/WI Freshwater Fish Specialist Group Secretariat of the Pacific Community Aquaculture Expert Consultation: Future Directions for Tilapia in the Pacific. (Noumea, New Caledonia 8 th - 11 th December 2009) Overview The value of tilapias The extinction crisis Recent discoveries The tilapia concern Pacific concerns from the past Connectivity and life history patterns in Oceanic island ecosystems Fiji case study Species most effected Causes of species loss Recommendations and way forward 1

2 The value of tilapias Second most widely farmed fish in the world (after carps) Value of tilapia as aquaculture commodity worldwide is about US$500 million By 2010, world tilapia production expected to be million metric tons Aquatic chicken Particularly in Asia, nearly all introduced tilapias produced consumed domestically In some Pacific locales (Fiji, PNG), significant part of rural diet Can be very profitable, where consumer acceptance is high and production practices are managed efficiently Market demand for tilapia in developed countries growing rapidly The extinction crisis ~28,000 fish species described (53% found in freshwater) 53 % of the world s fish species occur in only 0.01% of the planet s water Freshwater wetlands globally most threatened ecosystem type 37% freshwater fishes assessed threatened with extinction (2009 Redlist). Most threatened class of animal Species introduction and translocations are second only to habitat degradation as a cause of species extinction Oceania has exceptionally high concentrations of endemic freshwater species that are recognized as a global priority for freshwater conservation (Abell et. al. 2008) Natural heritage, direct ecosystem services and potential income opportunities often lost before they are realized 2

3 Recent discoveries Eleotridae, New Genus, Solomon Islands 2007 Stiphodon mele Kieth, Marquet, Pouilly 2009, (Vanuat New Caledonia) Sygnathidae, New Genus, Fiji, 2003 Lentipes solomonensis Jenkins, Allen, Boseto 2008 Lentipes venustus, Allen 2004, PNG Schismatogobius vitiensis Jenkins & Boseto 2005 The tilapia concern Adaptable to various water conditions, prolific breeders, territorial, able to feed at range of trophic levels outcompete native species Tilapias are highly invasive and exist under feral conditions in every nation in which they have been cultured or introduced Most introductions occur as consequence of aquaculture or part of stocking or fishery enhancement effort (FAO) Escape from culture cages, and even from carefully managed closed systems, through effluent drainage systems or as the result of a weather event, such as a flood or hurricane Establishment of rigorous containment systems can be costly and difficult 3

4 Pacific concerns from the past The introduction of tilapia was a disaster on nearly all Pacific Islands (Baird, 1976) The careless and needless introduction of the Mozambique tilapia has had no beneficial results... fishermen claimed that the introduction and subsequent spread of the Mozambique tilapia has resulted in a decrease of mullet, bonefish and milkfish (Lobel 1980) In Nauru, tilapia was not well received by the local people (Uwate et al. 1984) Several Pacific Islands governments perceive the eradication of tilapia as a priority fisheries project (Gillett, 1989)... poorly thought-out and poorly researched project with negative effect on the community concerned Government minister responsible for fisheries in Nauru (Iuta 1989) If only applied research on the ecology of tilapia had been conducted in Kiribati before the project was operationalised, such negative development could have been avoided Minister for Natural Resource Development (Iuta 1989) There can be serious consequences in encouraging unrealistically rapid progress in fisheries development (Gillett, 1989) Connectivity Between Ecosystems 4

5 Jenkins et. al Fiji Freshwater Fish Connectivity >98% of fishes utilize marine habitats during life cycles Jenkins et al

6 Most common life history pattern in tropical oceanic islands Most fishes on Pacific Islands cross multiple habitats during their lives Fishes like gudgeons live upstream most of their lives When larvae hatch from eggs, they swim and/or are washed out to the sea 6

7 Larvae spend a period of time feeding at sea before they come back upriver in a mass migration Larvae likely have reduced survivorship in rivers that are degraded & invaded Mass post-larval migrations provide important seasonal input to food webs and support locally important traditional fisheries (McDowall, 1984; Bell, 1999; Berrebi et al., 2005; Jenkins et. al 2009) post-larval migrants of sicydiine gobies and some eleotrid species can sell for up to $80-$110/kg Methods Fiji case study Study region 3 largest Fijian islands (MAR > 3200 mm Catchment sampling 50 m mid (n = 20) & lower (n = 8) reach of twenty river basins e-fishing, nets, snorkel Literature review & life history classification Boseto & Jenkins 2006 Life history Elliot et. al McDowell 2007 for amphidromy. Potential extent of habitat range Fiji vs NE Qld. (Russell et al. 2003) and mainland PNG (Coates 1993). Statistical analysis Predictors in best models included: catchment forest cover, distance upstream, maximum downstream slope, and presence/absence of tilapia Records of non-native introductions direct observation Fiji Freshwater Fishes Database + records of introduction from Fiji Department of Fisheries since

8 Hypotheses tested Insular fish fauna of Fiji -higher proportion of fish crossing at least three habitat types and including oceanic life history stages. Diversity of migratory fish is affected in regions with high anthropogenic disturbance from forest clearing and non-native species introductions, particularly among species with broad habitat ranges. Forest Cover in Fiji catchments 8

9 Invasive Fish in Fiji Catchments Spread in 60 odd years since introduction Jenkins et al Data on 89 (27%) (including all major catchments) 85.4% invaded 14.6% invasive free (Taveuni, Kubulau, Natewa, Western Kadavu) 98% Oreochromis spp, additionally Gambusia affinis, carp only Rewa catchment Results: Forest Cover and Tilapia Fewer numbers of native fish species in catchment with less forest cover Fewer numbers of native fish species in catchment streams with tilapia Community management can help preserve species richness Jenkins et al

10 Results: Tilapia only In streams with tilapia, there are on average 11 fewer species of native fish Most effected species Gobiidae (Gobies) and Eleotridae (Gudgeons) primarily 5 of 9 Fijian endemic gobies locally extirpated Loss of aquarium potential income + natural heritage? 10

11 Most effected species Loss of traditional inland food options and natural heritage? Causes of fish species loss Sediment smothers resting habitat Sediment smothers food sources Tilapia stir up bottom sediment during nesting and foraging bioturbation + space competition Tilapia eat fish eggs, larvae and small adults Harder for fish to see where prey or predators are located Fish that have to cross the greatest number of habitats have the highest likelihood of being affected Supporting literature: Starling et al. 2002; Canonicoet al. 2005, McKayeet al. 1995, DOUPÉ, R. G. et al 2009; Jenkins et. al

12 Some conclusions Tilapias have heavily invaded the waterways of Fiji Invasion combined with loss of forest cover severe reductions in species diversity and ecological connectivity Tropical high islands need terrestrial, freshwater and marine systems to be studied and managed together at the scale of connectivity processes (EBM) Despite potential socioeconomic benefits, tilapia aquaculture and open-water introductions cannot continue unchecked without further exacerbating damage Encourage and support traditional, community-based management of catchment areas (traditional tenure) Assisting National Planning Blue areas:there is good connectivity between terrestrial, freshwater and marine areas. To preserve this connectivity, set up tabu areas on the land, around streams and in the sea. Coastal areas around Nadi, Ba & Labasa suffered from extreme flooding damage in Jan 09 Orange areas:connectivity has broken down here. Need to improve land management practices and focus on restoration. 12

13 Recommendations More emphasis and resources on the use of native species in aquaculture and stocking programmes eg. Milkfish, Siganids, Eleotrids, Anguillids Tap into US$1Billion aquarium fish industry (Gobiids, Eleotrids) Minimize/eliminate introduction of all non-native species, particularly in locations where endemic and threatened species occur Distribution patterns of native species mapped, and disseminated for use in planning aquaculture programmes Identify invasive-free catchments as priorities for conservation Tilapias should be raised in contained ponds with no access to natural waters Investigate facilities with no record of local establishments to document best management practices or guidelines specific to tilapia aquaculture Aquatic ecosystems and human need generally poorly studied prior to tilapia introductions. Sufficient baseline of native fauna and socioeconomics necessary for interpretation of risk and impacts FAO Code of Conduct for Responsible Fisheries Article calls on states to conserve genetic diversity and maintain integrity of aquatic communities and ecosystems by appropriate management Article 7.5 calls on states to apply the precautionary approach widely to conservation, management and exploitation of living aquatic resources in order to protect them and preserve the aquatic environment. Need for a regional and taxon specific instrument? 13

14 Way forward Representatives to Heads of Fisheries are requested to support the SPC-HoF Principles for Aquatic Organisms Introduction and Translocation for Aquaculture and Culture-Based Fisheries, 2003 Ponia et. al Species that cannot feasibly be eradicated or controlled biologically, especially species whose value to people prevents the use of biocontrol, should be contained within delimited areas or excluded from important areas, where feasible (SPREP, 2009) Work together to develop a regional code of conduct and risk assessment protocol specific to tilapias Make more resources available for careful national planning and monitoring of aquaculture developments and diversification While there may be compelling humanitarian arguments to exploit high yield, low-cost sources of protein in the short term, conservation of environmental capital, or the natural resource base, is necessary from the viewpoint of economics and long-term sustainability (Tisdell, 1999). THANK YOU! 14