the humboldt current system of northern and central chile - figema

MARTIN THIEL ET AL.known about the influence of oceanographic factors on recruitment success and stock dynamics ofcrustaceans from the continental shelf off northern-central Chile. Most current information suggeststhat their life history is driven by seasonal factors, and presently available data do not permit anexamination of the effects of interannual variability in oceanographic conditions (e.g., ENSO) ontheir population dynamics. Future studies should address these questions in order to achieve asustainable fishery.Pelagic fisheries and fisheries management, 1980–2005The Chilean purse seine fleet mainly exploits five pelagic fish species: anchovy (Engraulis ringens),jack mackerel (Trachurus murphyi), chub mackerel (Scomber japonicus), and Pacific sardine orpilchard (Sardinops sagax) and common sardine (Strangomera bentincki). There were doubts aboutthe taxonomic status of jack mackerel (Stepien & Rosenblatt 1996, Oyarzún 1998), but a recentmolecular study revealed that the name Trachurus murphyi should be conserved (Poulin et al. 2004).In the official landing statistics it is also recorded as T. murphyi, but the Technical Reports of theUndersecretary of Fisheries refer to it as T. symmetricus.History of the catchesAguilar et al. (2000) described the development of the Chilean pelagic fisheries based on thelandings of anchovy, jack mackerel and pilchard from 1970 to 1995. Herein the period from 1995to 2005 (also known as the ‘regulated’ period) is included, which adds two additional species: chubmackerel and common sardine, and their landings since 1980.The total annual landings captured by the Chilean purse seine fleet during the study period showeda steadily increasing tendency from 1980 until 1995, from 3.4 million t to almost 6.9 million t,driven mainly by the increase in jack mackerel landings and secondarily by anchovy landings,which replaced the Pacific sardine, the most important species during the early 1980s (Figure 26).After that, the total annual catch decreased to around the same level found at the beginning of thestudy period, with the exception of 1998, when both species simultaneously showed a sharp declinein their landings. However, as stated, these are ‘regulated’ landings since catches are the result offixed total annual quotas and therefore not necessarily representative of resource availability.Administratively, four of the five species included in this analysis are latitudinally assignedto fisheries units, each of which comprises two to five administrative zones: Regions I–II(18°25′S–26°06′S), Regions III–IV (26°06′S–32°18′S), Regions V–IX (32°18′S–39°37′S) andRegions X–XII (39°37′S–56°30′S), and there is a strong difference in landings between the respectivefishery units (Figure 26). Therefore, annual landings are analysed by species and these latitudinalfisheries units to visualise their importance in each of them. In the following text each FisheriesUnit is defined by the Regions it contains, e.g., Fisheries Unit I-II.Landing statistics of anchovy show the typical characteristics of engraulids, with successiveincreases and decreases, attaining highest landings of 2.7 million t in 1994, but landings usuallydo not surpass 1.5 million t. Anchovy landings are most important in northern Chile (FisheriesUnit I–II) (Figure 27). In contrast to all other species, jack mackerel showed a continuous increaseuntil 1995, when annual landings reached 4.4 million t, after which catches continuously decreasedagain. Throughout this period, catches in central-southern Chile (Fisheries Unit V–IX) had overridingimportance (Figure 27). The highest landings of chub mackerel were attained in 2003 with0.5 million t. This species has shown a steady increase in landings during the study period. At thebeginning of the period, landings of chub mackerel were mainly in northern Chile (FisheriesUnit I–II) but since the year 2000 also increased in central-southern Chile (Fisheries Unit V–IX)288