An update on the catch composition and other aspects of cetacean exploitation in Ghana

Photographs of 231 landed specimens (212 identifiable) were analysed to determine species composition of cetacean take in Ghana’s artisanal fisheries in 1995-2010, the most comprehensive sample documented in West Africa. The three most commonly landed species are: 24.5% Clymene dolphin (Stenella clymene), 13.2% pantropical spotted dolphin (Stenella attenuata), 12.3% common bottlenose dolphin (Tursiops truncatus). Also regularly caught are: 10.4% melon-headed whale (Peponocephala electra), 9.4% short-finned pilot whale (Globicephala macrorhynchus), 9.4% long-beaked common dolphin (Delphinus capensis). Occasionally landed are: 6.1% rough-toothed dolphin (Steno bredanensis), 4.7% Risso’ s dolphin (Grampus griseus), 3.1% kogiids (including Kogia sima) and 2.8% spinner dolphin (Stenella longirostris). Rarely (< 2%) landed are: Atlantic spotted dolphin (Stenella frontalis), Fraser’s dolphin (Lagenodelphis hosei), false killer whale (Pseudorca crassidens) and pygmy killer whale (Feresa attenuata). One small sperm whale was recorded taken offshore. Catch rate estimators, cetaceans landed per month (cpm) and cetaceans landed per day (cpd) were derived for 3 ports, but the national situation is unknown. At Axim, in 23 months, 130 cetaceans were observed landed (mean 5.65 ±SE 1.19 cpm); prorated per annum, 67.8 ±SE 14.28. During high-intensity surveying Jan-Nov 2003, 52 cetaceans were recorded in 192 days, with mean daily landings 0.271 cpd, prorated per annum 99.0. Reported landings at Axim in Aug-Dec 2007 were limited (0.087 cpd), prorated per annum 31.8 cetaceans, however a negative sampling bias was indicated making this cpd questionable. At Apam in 1995-99 mean monthly landings were a very low 1.117 (±SE 0.23 cpm); prorated per annum 13.40 (±SE 2.76) cetaceans. In Oct 2001-Oct 2003, 128 cetaceans were observed, ie mean monthly landings 5.57 ±SE 1.29 cpm (n=23, range 1-25), prorated per annum 66.84 (±SE 15.48). Intensive surveying in Jan-Nov 2003 saw 87 cetaceans landed on 267 days, or 0.362 cpd; prorated per annum 132.22. The cpm in 2001-03 increased very significantly compared to 1995-99. Highest catches occurred at Dixcove: in 25 months (Oct 2001-Oct 2003) 564 cetaceans were observed, mean monthly landings 22.56 ±SE 3.26 cpm (n=25, range 6-69), prorated per annum 270.72 ±SE 39.12 cetaceans. Mean daily landings rate 0.74 cpd. In 2009-10, daily landings became the norm with frequent multiple landings; highest one-day catch > 20 dolphins. In April 2010, of 9 cetaceans landed in 7 days, 3 were butchered before a team could document them, supporting caveat that observed landings underestimate true landings. An intensive biological sampling programme and nation-wide recording of cetacean captures are needed immediately, to guide the formulation and implementation of effective management and conservation measures. The paper also notes: The Atlantic humpback dolphin Sousa teuszii has been consistently absent from records since port surveillance started (Ofori-Danson et al., 2003; Van Waerebeek et al., 2003, 2009). A historic population collapse due to by-catches predating monitoring has been suggested (Van Waerebeek et al., 2004). The species’ preference for shallow, nearshore and estuarine habitat would render it particularly vulnerable to ubiquitous inshore set gillnets, beach seines and other anthropogenic disturbances. Alternatively, a natural distribution gap may exist off Ghana/Togo related to periodical cool upwelling.