Demersal fish in the Canary Current Large Marine Ecosystem Item Type Report Section Authors Fernández-Peralta, Lourdes; Sidibé, Aboubacar Publisher IOC-UNESCO Download date 27/09/2021 12:36:46 Link to Item http://hdl.handle.net/1834/9190 5.2. Demersal fish in the Canary Current Large Marine Ecosystem For bibliographic purposes, this article should be cited as: Fernández‐Peralta, L. and Sidibé, A. 2015. Demersal fish in the Canary Current Large Marine Ecosystem. In: Oceanographic and biological features in the Canary Current Large Marine Ecosystem. Valdés, L. and Déniz‐González, I. (eds). IOC‐UNESCO, Paris. IOC Technical Series, No. 115, pp. 215‐229. URI: http://hdl.handle.net/1834/9190. The publication should be cited as follows: Valdés, L. and Déniz‐González, I. (eds). 2015. Oceanographic and biological features in the Canary Current Large Marine Ecosystem. IOC‐UNESCO, Paris. IOC Technical Series, No. 115: 383 pp. URI: http://hdl.handle.net/1834/9135. The report Oceanographic and biological features in the Canary Current Large Marine Ecosystem and its separate parts are available on‐line at: http://www.unesco.org/new/en/ioc/ts115. The bibliography of the entire publication is listed in alphabetical order on pages 351‐379. The bibliography cited in this particular article was extracted from the full bibliography and is listed in alphabetical order at the end of this offprint, in unnumbered pages. ABSTRACT Demersal ichthyofauna is both the most diverse and the most abundant component in terms of biomass, of the marine shelf and slope ecosystems. Within the Canary Current Large Marine Ecosystem (CCLME), Northwestern African waters hold a fish fauna even more diverse than that of Northeast Atlantic. The convergence of ichthyofaunal components of both temperate and tropical affinities results in a very biodiverse central zone, mainly in Mauritanian waters, where the transition from one faunal type to another is observed. The CCLME supports substantial demersal fish resources whose total catches decline constantly. The FAO assessments show that many important stocks are here overexploited. Species richness is minimum in waters shallower than 400 m, probably due to the heavy fishing pressure exerted over the shelf and upper slope in past decades. Conversely, deep waters are the most biodiverse, particularly between 1000 m and 1700 m depth. Northwestern African waters need to be managed both to avoid overexploitation and to ensure the protection of highly vulnerable species living on very sensitive marine ecosystems of the middle and deep continental slopes, still unexploited. A great effort of cooperation within the various actors involved in the regional fishing policies is required to ensure a sustainable management of the marine resources. Keywords: Demersal fish · Biodiversity · Fisheries · Connental shelf · Continental slope · Canary Current Large Marine Ecosystem · Northwest Africa IOC TECHNICAL SERIES, No. 115, pp. 215‐229. URI: http://hdl.handle.net/1834/9190. 2015 DEMERSAL FISH IN THE CANARY CURRENT LARGE MARINE ECOSYSTEM Lourdes FERNÁNDEZ‐PERALTA1 and Aboubacar SIDIBÉ2 1 Centro Oceanográfico de Málaga, Instituto Español de Oceanografía. Spain 2 African Union‐Interafrican Bureau for Animal Resources (AU‐IBAR), African Union Commission (AUC). Kenya 5.2.1. INTRODUCTION Until the late 20th century, 90% of the world´s fisheries were in shelf seas. Although upwelling zones made up only 0.1% of worldwide shelf areas, they account over 50% of total catches (Granado Lorencio, 1996). This reflects the significance of major upwelling ecosystems such as the Canary Current Large Marine Ecosystem (CCLME) region, characterized by high biological diversity and significant fisheries resources, which are heavily exploited. Beginning in the 1990s, the fishing pressure on continental shelves led to a displacement of fisheries towards increasingly deeper waters in several parts of the world (Piñeiro et al., 2001), and this is extensive to Large Marine Ecosystems (LME) (Fernández‐Peralta et al., 2011b, submitted; Fernández‐Peralta and Puerto González, submitted). Demersal ichthyofauna is one of the largest components of marine ecosystems in terms of biomass and biodiversity, and it is very important economically. The role of demersal fish as predators determines the state of lower trophic levels in the food chain, showing that the top‐down trophic cascade (Northcote, 1988) is the key factor in the structure of communities (Granado Lorencio, 1996). Despite the importance of demersal fish in the CCLME region, there are very few biogeographical studies in comparison with other regions such as the North Atlantic. The first studies on this fauna in north‐western Africa (NWA), carried out between 1850 and 1950, merely prospected some very shallow waters above the shelf, down to a maximum of 200 m. Highlight the campaigns carried out to this depth in 1936 between Villa Cisneros (now Dakhla) and Sierra Leone in the Président Théodore Tissier (Cadenat, 1937; Belloc, 1938) or in the Belgian vessel Mercator (Poll, 1949). The first information available on the deeper demersal fish in NWA comes from the campaigns of the Gérard Treca, where for the first time sampling was done over the upper slopes (Cadenat, 1953). This was followed by the campaigns of the Thalassa in 1962, 1968, 1971 and 1973 (Maurin and Bonnet, 1970; Maurin and Quero, 1981), and the campaign of the Discovery in 1976 (Merrett and Domanski, 1985). See Van der Knaap (1985) for a comprehensive list of historical surveys, although detailed information on sampling and data is not available. The Thalassa surveys, carried out from Cape Juby to Cape Verde were the first prospections to depths of 800 m and they published the first inventories and the most complete ichthyological notes in Mauritanian waters (Maigret et al., 1981). Various campaigns over the shelf and upper slopes conducted in 1982 and 1983 by the Mauritanian vessel N’Diago and research vessels of the Fisheries Institute of Rostock (German Democratic Republic) enabled Gaudechoux and Richer de Forges (1983) to produce an exhaustive ichthyological inventory of those waters. The Guinean Trawling Survey campaigns (1964‐65) were carried out over the shelf and upper slopes of the Gulf of Guinea, outside the CCLME region and they led to the description of tropical demersal fish communities (Williams, 1968; Longhurst, 1969), and many of the species extend as far as the latitude of Cape Blanc. Ramos et al. (1991) provide the most recent information on these demersal communities. 215 Fernández‐Peralta, L. and Sidibé, A. Demersal ichthyofauna of Northwest Africa Campaigns conducted between 2002 and 2010 by the Vizconde de Eza in Moroccan and Mauritanian waters (down to a depth of 2000 m) and in Guinea‐Bissau, down to 1000 m (Hernández‐González et al., 2006, 2010; Hernández‐González, 2007; García‐Isarch et al., 2011; Ramos et al., 2005, 2010) provided valuable information on fish communities (Fernández‐Peralta et al., 2008a; Fernández‐Peralta and Puerto González, submitted; Puerto et al., 2012). Lastly, campaigns conducted on board the Dr. Fridtjof Nansen in 2011 and 2012 in the CCLME region provided important overall information on fish communities from coastal waters to the slope. Demersal fish resources have been exploited on a small scale in NWA, first in northern Morocco by Portuguese and Spanish fishermen, who reached Western Sahara waters as early as in 15th century (Balguerías et al., 2000). In the 20th century, the first industrial fisheries began to be developed by foreign fleets extending their ranges as far as the south of the African coast, at the same time the CCLME countries have gradually developed their own small‐scale and industrial fisheries. These demersal fish constitute vital renewable natural resources providing food and income for the local population, foreign exchange earnings, revenue for national governments (balance of payments) and employment opportunities in the CCLME countries. The region’s coastal‐shelf species have been seriously overfished (FAO, in press a, b; Gascuel et al., 2007; Meissa and Gascuel, 2014), leading to a risk that fleets will move to deeper waters, as it which is already occurring (Fernández‐Peralta et al., submitted; Fernández‐Peralta and Puerto González, submitted). Knowledge of fish stocks as a whole is vital for maintaining biodiversity. The scientific monitoring of these demersal species is crucial for their protection and sustainable management. This study presents a characterization of the demersal ichthyofauna in the CCLME based on a review of available data. The conclusions provide practical information for the management and biodiversity conservation of the fishery resources of this productive area in a holistic perspective (Jennings, 2004). 5.2.2. METHODS The data sources used for the characterization of the demersal ichthyofauna in the CCLME were: ‐ Unpublished results of many surveys carried out in the region. ‐ Literature review of the main papers available on demersal fish species researched in the area. ‐ The IEO bottom trawls surveys onboard the R/V Vizconde de Eza carried out off Morocco (in 2004 and 2005) (Ramos et al., 2005; Hernández‐González et al., 2006), Western Sahara (Hernández‐González, 2007), Mauritania (2007 to 2010) (Hernández‐González et al., 2010; Ramos et al., 2010) and Guinea‐ Bissau (2002 and 2010) (García‐Isarch et al., 2011). The depths ranged from 500 m to 1850 m (Morocco), 200 m to 1860 m (Western Sahara), 80 m to 1860 m (Mauritania) (Déniz‐González