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Poster [pdf version 8.3mb]
Deep Water Fauna of the Galápagos Archipelago - Implications for Deep-Water Fisheries
Waller, Shank, Fornari, Kurz and Pomponi
The Galápagos Islands are situated in the Eastern Equatorial Pacific, approximately 600 miles west of the coast of South America. The archipelago is made up of 123 islands, with Santa Cruz Island, the most inhabited, being in the centre (Snell, 1996). These islands have been of intense interest to biologists and geologists since the sailing of the Beagle to the islands in 1835. They are of particular interest to geologists and geochemists, as unlike other oceanic intraplate volcanism (i.e. Hawaii, the Azores), volcanoes throughout the archipelago are still presently active. The islands are on top of the Galápagos Hotspot, an area where the mantle plume rises to the surface (Kurz & Geist, 1999). The active volcanism on the islands has led to a diverse and ever changing environment, both terrestrially and sublittorially. The fauna inhabiting the islands has had to adapt to these regular changes in environment, leading to a great number of terrestrial and shallow water endemic species.
The archipelago also lies in the transitional zone of the eastern tropical Pacific, with three major currents merging at this point. In the south the nutrient rich Humbolt current upwells and flows out to the west with the South Equatorial Current (SEC). In the north, the Californian current flows down the coast of America, and then also turns and spreads west with the SEC. Under the SEC, the Equatorial Undercurrent brings in cold deep, nutrient rich, water that upwells at the islands (Steger et al., 1998). It is the convergence of these three distinct water masses that has transported marine organisms from the tropical and subtropical Pacific as well as the Indo-Pacific (Robinson, 1987). Water temperature around the islands has been shown to be up to 4 degrees Celsius higher north of the equator (Hoge et al., 1998). The coolest waters around the islands can be found south of Isabela (including Santa Maria Island), extending upwards on the west coast to Fernandina Island (Steger et al., 1998). Wolf, Darwin, Marchena, Genovesa and Santa Cruz Islands all have warmer waters surrounding them (Reed & Pomponi, 1996; Steger et al., 1998). It is these three flows, and the temperature differences, that create different marine habitats around the various islands (Mares, 1982; Robinson, 1987).
In 1998 the Ecuadorian government enacted a special legislation (the Galápagos Special Law) to promote the conservation of biodiversity and sustainable development of the Galápagos islands. A major section of this law encompasses the large marine realm surrounding the islands. A Marine Reserve was established (managed by the Galápagos National Park Service (GNPS)) that encompassed a 40mile radius around the whole archipelago and covers 133,000 square kilometres. Within this area only tourism and local artisanal fishing is allowed. This law was seen as a breakthrough, protecting and conserving the world’s largest marine reserve.
However, there was, and still is, intense opposition from the industrial fishing sector. Since 1998 there have been increasing violence by fishermen wanting to reopen parts of the park to fishing, putting increasing pressure on the Ecuadorian government. The population of the Galápagos islands expands by 5.8% per year, whereas mainland Ecuador only expands by 2.1%, with much of this population relying on tourism or fishing. The latest strike by fishermen in June of this year, saw the research facilities on Isabella and Santa Cruz being seized for over a week. This ended with the Ecuadorian government promising to relax fishing regulations, however, after world protestation by NGO’s, this agreement was retracted, the minister for the environment resigned and the new minister agreed to follow the limits of Galapágos Special Law by addressing the needs of the fishermen within the participatory management process.
With this increased pressure mounting on the Ecuadorian government to re-open fisheries, it is increasingly important to more fully understand the deep water habitats and fauna surrounding the archipelago. This poster presents data from four cruises to the deep-water areas surrounding the Galápagos Islands.
There has recently been four major cruises around the Galápagos islands collecting deep-water fauna (Reed & Pomponi, 1986; Reed & Pomponi, 1996; Kurz et al., 2001). In 1986 and 1995, Harbor Branch Oceanographic Institution’s Johnson SeaLink submersible took both shallow and deep-water samples from around the archipelago. These cruises were mainly focused on the development of novel pharmaceutical products, and so concentrated on the Porifera and Cnidaria. Extensive collections of other phyla were also recovered, mainly during the 1986 cruise. These cruises sampled down to 900m water depth.
In 2000 and 2001 scientists from the Woods Hole Oceanographic Institution visited the deep-waters surrounding the islands on geological expeditions. The main focus of this work was to collect basalt from various submerged lava flows, mainly around Fernandina, for geochemical analysis. Collections of basalts were made by rock dredge and glass corer down to 4500m depth. Any fauna that was recovered was catalogued and preserved. There was also one camera tow during this cruise using the WHOI Digital Towed Camera System. Larger fauna that could be identified from the digital pictures are also included in the species list and analysis.
These four cruises make up the only known extensive collection of deep-water fauna from the Galápagos archipelago. The poster presents a listing of genera collected during these cruises, as well as PAUP analysis to examine similarities in species composition between islands. The islands separated north to south for analysis, with Isabela, the largest island, being split into Northern, Middle and Southern areas.
- 294 species were collected during these four cruises, comprising
the largest collection of deep-water fauna from this area.
- The cnidaria were most abundant in collections, with the echinodermata
being second and the porifera third. It must be noted however
that these phyla were targeted by the Johnson Sealink Cruises
for their pharmaceutical potential, and so numbers are highly
- Deep water coral habiats were found in a number of locations.
On a pinnacle north of Genovesa, there were two deep-water reef
building species brought up with dredge samples during the DRIFT4
cruise, 2001. Numerous soft corals were also collected and observed
by all four cruises. Long lining is at present being trialled
in the Marine Reserve. Though the major impact of this fishing
method is shark bycatch, numerous studies have looked into the
potential impacts of fishing, both by long line and trawl, on
ecosystems, particularly coral communities (Hagler, 1995; Gubbay
et al., 2002). Deep water corals have been shown to harbor an
array of commercially important fish species that use these
biomes for feeding, protection and procreation (Rogers, 1999).
- A UPGMA tree was generated in PAUP. This tree shows species compostion of Wolf to be most dissimilar to Roca Redonda, and most similar to San Cristobal. As fauna was collected by different methods on each cruise, this is an initial assesment of faunal diversity of the deep water provinces of the Galápagos. Though it does not show a faunal break as found in the shallow water, it does show that each island may have a distinctly different fauna. Further analysis of the currents in this area are being undertaken to more fully understand the faunal provinces described by this analysis.
- These four cruises present the first insights on the deep water fauna of the Galápagos archipelago. The results show there to be a diverse fauna surrounding the islands, with many species yet unidentified and so there is a high potential for deep water endemic species.
- Analysis showed no two islands to be identical in species composition, with Northern Isabella and Roca Redonda sharing the most numbers of species - likely a consequence of them being the spacially closest islands.
- The importance of knowing the deep-water fauna comes at a time when an extension of fisheries to these areas is being considered. By understanding the deep-water ecosystem, potential impacts of this decision can be properly assessed.
We would like to extend our gratitutude to the Galápagos National Park Service and to the Charles Darwin Research Center, at Pt Ayora, Santa Cruise Island for assistance before and during cruises. We would also like to thank the Captains, crew and scientists of the RV Seward Johnson, the RV Knorr and the RV Roger Revelle for these four cruises. Many taxonomists also identified the numerous specimens from all four cruises and are gratefully acknowledged - D. Billet (Holothurians – DRIFT 4); S.Cairns (Gorgonians – JSL); C. and F. Monniot (Ascidians – JSL); Rieman-Zurneck (Actinarians – JSL); Maldonado (Porifera – JSL); Reed (Gorgonians – JSL). This work was supported by NSF.