The Jumbo flying squid Dosidicus gigas has a short life span and is subject to rapid changes in population size. This species inhabits the Eastern Pacific, one of the most variable oceanic environments in the world, subject to the El Niño Southern Oscillation (ENSO). This study examined the influence of environmental variability on squid abundance off Peru using mesoscale oceanographic indicators derived from remotely sensed satellite imagery. In the fishery area off Peru, squid abundance was positively associated with sea surface temperatures (SST) between 17 and 22°C during July, corresponding to the peak of the fishery season. In the putative hatching area close to the Costa Rica Dome, squid abundance was positively associated with SST of between 24 and 28°C during September, prior to the start of the fishery season. Squid abundance is apparently strongly influenced by mesoscale variability linked to ENSO, with low levels of upwelling during the very strong El Niño of 1997 to 1998 leading to very low catches of squid off Peru. Variability in upwelling off Peru and in the Costa Rica Dome region may drive primary and secondary production and transport processes affecting the planktonic early life stages and also the availability of food and suitable habitat for adult squid.KEY WORDS: Costa Rica Dome · Dosidicus gigas · El Niño Southern Oscillation · Eastern Pacific · Fishery · Flying squid · Mesoscale oceanography · Upwelling
Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 310: [25][26][27][28][29][30][31][32] 2006 lower thermocline, the upwelling of cool, nutrient-rich waters, and high primary productivity (Barber & Chavez 1983, Carr et al. 2002. During warming (El Niño) events, the trade winds weaken and are replaced by westerlies at low latitudes (Longhurst 1998). In addition, the thermocline is depressed and upwelling consists of nutrient-depleted waters, such that productivity is reduced (Barber & Chavez 1983, Huyer et al. 1987. At the equator, 3 currents arise, the westward-flowing North and South Equatorial Currents, and the eastward-flowing Equatorial Counter Current, which bifurcates as it nears the continental margin, giving rise to the Costa Rica Dome. The Dome is an area where the generally strong and shallow thermocline of the eastern tropical Pacific becomes even shallower, with cold nutrient-rich water occurring close to the surface (Wyrtki 1964, Fiedler 2002. This is an area of high productivity, with a regional maximum in chlorophyll concentration in surface waters from May to September, and an associated high abundance of zooplankton (Fiedler 2002).Dosidicus gigas is a eurythermic species, with a usual temperature range of between 15 and 28°C (Nesis 1983), although squid have been found to tolerate extremes of between 4 and 32°C in the deep ocean and equatorial waters respectively (Nigmatullin et al. 2001). The highest concentrations of squid have been recorded at temperatures of between 24 and 29°C in the northern hemisphere (Nesis ...