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Investigaciones marinas

versión On-line ISSN 0717-7178

Investig. mar. v.30 n.1 supl.Symp Valparaíso ago. 2002

http://dx.doi.org/10.4067/S0717-71782002030100033 

Warm ENSO Events and their Effects
on the Coastal Fish Fauna of
Northern Chile

Walter Sielfeld, Mauricio Vargas,
Viviana Berrios, Gabriela Aguirre

Departamento Ciencias del Mar, Universidad Arturo
Prat, Casilla 121, Iquique, Chile,
E-mail: wsielfeld@cec.unap.cl

Introduction

Changes in composition and structure of fish communities of the sandy and rocky shores of Northern Chile are discussed in relation to warm El Niño events. The research covered the seashore and the coastal pelagic zone, with collection of fish between Chipana beach (70 km south of Iquique port, Chile) and Las Machas beach, 10 km north of Arica port, Chile), and seasonal samplings at the localities of Chipana beach, Blanca beach and Punta Patache. The data were obtained between 1984 and 2002. For sampling in the sandy shore a "chinchorro de playa" net with a length of 50 m was used. Fish in tide pools were studied using BZ - 20 anasthaetic. Fish of the sublittoral were sampled using Scuba diving equipment. Additionally, historic information and results of diverse fish collections not directly related to this study were considered, including bibliographic sources (Mann, 1954; Fowler, 1945; de Buen, 1953, 1957, 1959; Delfin, 1899, 1901; Guichenot, 1848; Kong et al, 1985; Kong & Valdés, 1990; Soto & Zapata, 1984), underwater fishing competitions, and bycatch monitoring of the regional fisheries.

LOCALITY

Arica

Pisagua

Iquique

Chipana

Tocopilla

Mejillones

Antofagasta

 

Nº SPECIES

89

80

79

53

44

42

36

ENSO

1982/83

1986/87

1991/92

1997/98

Anormaly

+ 5.5 ºC

+2,5ªC

+ 4.0ºC

+ 5,0ºC

Nº SPECIES

57

11

23

36

Results

The analyses of the information presented by Kong et al. (1985), Sielfeld et al. (1995), Vargas et al. (1998) and Vargas & Sielfeld (1999), indicate 94 fish species, corresponding to 46 families, associated in Northern Chile with warm ENSO events that occurred between 1982 and 2002.

Most of the species (55) are coastal epipelagic, and probably migrate with water masses and in consequence are very mobile. The littoral species include 24 species exclusive to sandy beaches, represented mainly by the family Sciaenidae, a dominant group in this system (Vargas, 1998), and 16 species inhabiting the rocky shore.

The distribution of these septentrional invading species (sensu Mann, 1954) according to its southward migration degree during the warm events, shows a north/south gradient that reinforces the transitional character of Northern Chile between the Chilean and Peruvian Zooprovinces indicated by Sielfeld & Vargas (1996) for benthodemersal fish assamblages.

The distribution of the invading species during warm ENSO periods shows a direct relation between thermal anomaly and number of species.

The species that are triggered by ENSO events are not always the same. Only the following epipelagic species were found to be associasted to all of the last three ENSO events: Anchoa naso, Albula vulpes, Atherinella nocturna and Scomberesox stolatus. The shore fish communities seem to be very stable, and only Umbrina xantii was found during all of the events considered.

Rocky shore

Following Aguirre (2001), the fish assamblage associated with the Lessonia trabeculata kelp bed of the rocky subtidal zone south of Iquique is normally represented by 23 species during cold events. Outstanding species in terms of abundance are Anisotremus scapularis (22%), Cheilodactylus variegatus (13%) and Paralabrax humeralis (12%). The remaining species are only accidental, whereby 11 species show an abundance less than 0,01%, and Hemilutjanus macropthalmus, Aplodactylus punctatus, Mugiloides chilensis and Neoxilosus latifrons between 2% and 6%. All these species are resident, with the exception of P. humeralis, an occassional visitor that forms schools, explaining its high abundance.

During ENSO events, the structure of the fish assemblage is modified by the addition of low latitude species. Along the study area the following species were detected: Aluterus monocerus, Balistes polylepis and Chaetodon humeralis (during the 83/84 period), Bodianus eclancheri and Halichoeres dispilus (during the 87/88 period), Sphoeroides lobatus and Sphoeroides trichocephalus (during the 88/89 period), Scorpaena hystrio (during the 96 and 99 periods) and Labriosomus xantii and Antennarius avalonis (during the 98/99 period). Their presence was mostly represented by solitary specimens. These species probably remain in the zone after the decline of the ENSO event, and explain the presence of B. polypelis and H. dispilus reported by Aguirre (op. cit.) for the 2000/2001 period.

The intertidal pools of the rocky shore have been considered as important breeding places for subtidal fish (Varas & Ojeda, 1990; Berrios & Vargas,1999). In Northern Chile, these sites normally show high abundance (>50%) and frequency (100%) of Girella laevifrons, principally in its juvenile phase, followed in importance by Scartichthys gigas and S. viridis, which, along with Helcogrammoides chilensis and Auchenionchus microcirrhis, are resident species. They were found to stay in the pools even during strong ENSO events.

The increase in sea temperature during El Niño 1997/98 favoured the presence of the following warm water species in the study area: Oplegnathus insignis, Cheilodactylus variegatus, Nexilosus latifrons and Anisotremus scapularis. The young enter the pools during spring, reaching frequencies of 38%, 38%, 46% and 76% respectively. A. scapularis may become very abundant (from 2 to 107 individuals), agreeing with similar observations made in sandy beaches by Vargas & Sielfeld (1998), during the same period.

Sandy beaches

In cold, inter-El Niño conditions the fish assamblage was modified, with A. scapularis and O. insignis disappearing, and Labrisomus philippi and C. variegates decreasing in abundance, possibly because of their preference for temperate waters (Hildebrand 1946, Mann 1954, Chirichigno 1974). Chromis crusma and Graus nigra increased in abundance, and at least the latter specie is typical of the colder water of Central Chile. In these conditions the young of N. latifrons delay their arrival until the end of summer or beginning of autumn.

During the 1989/90 cold episode the capture frequencies of fish at Chipana beach (latitude 21º 19´S) included 9 resident species, 10 seasonal species and 12 occasional species (Vargas, 1993; Vargas and Sielfeld, 1997). Names of species and capture frequencies are indicated in Table 1.

Table 1 Captures of fish at Chipana beach

RESIDENT FISH

SEASONAL FISH

OCCASIONAL FISH

Austromenidia regia (100,0 %)

Sardinops sagax (60,0%)

Paralabrax humeralis (33,3%)

Menticirrhus ophicephalus (100,0 %)

Mustelus mento (60,0%)

Doydixodon laevifrons (26,7%)

Sciaena deliciosa (100,0 %)

Engraulis ringens (60,0%)

Anchoa naso (26,7%)

Brevoortia maculata (100,0 %)

Mugil cephalus (53,3%)

Sciaena fasciata (20,0%)

Paralichthys adspersus (86,7%)

Scomber japonicus (40,0%)

Triakis maculata (13,3%)

Cilus gilberti (80,0%)

Trachurus murphyi (40,0%)

Normanichthys crockeri (6,7%)

Isacia conceptionis (73,3%)

Syngnathus acicularis (26,7%)

Seriolella violacea (6,7%)

Anisotremus scapularis (66,7%)

Aphos porosus (20,0%)

Cynoscion analis (6,7%)

Trachinotus paitensis (60,0%)

Acanthistius pictus (20,0%)

Callorhynchus callorhynchus (6,7%)

 

Rhinobatos planiceps (13,3%)

Sympterygia brevicaudata

   

Thyrsites atun (6,7%)

   

Nectarghes nocturnus (6,7%)

In terms of numerical abundance during an annual cycle, the most important species were Brevoortia maculata (34,9%), Sardinops sagax (23,4%), Austomedinida regia (20,6%) and Isacia conceptionis (6,1%). Other species showed values under 2%. The most diverse family was Sciaenidae (3,9% of total fish), the most important being Menticirrhus ophicephalus (1,7%) and Sciaena deliciosa (1,4%).

During El Niño 91/92 and 97/98, a reduction of fish density in terms of capture per haul was observed as a first response of the fish community. Particular species affected by El Niño 91/92 included S. sagax with a general reduction to 0,8% of the annual catch in 1991 and none in 1992. In 1994 its abundance rose again to 44,7%.

M. ophicephalus mantained its normal abundance during 1991 (1,9%), but increased in 1992 to 34,1% of the total catch. In 1994 the abundance went down again to 0,5%. The same situation was found for C. gilberti which, in 1992, reached an abundance of 20,8%, while in 1989, 1990 and 1991 values of 0,6 - 0,8% were normal. In 1994 the species disappeared from catches.

Several unusual warm water immigrants were caught during El Niño events. Their abundance in most cases was very low. Characteristic pelagic species were Naucrates ductor, Opistonema libertate, Belone stolzmanni, Strongylura exilis and Selene brevoorti (82/83; 97/98), Anchoa naso, Atherinella nocturna, Etrumeus teres and Scomberesox saurus (82/83; 91/92; 97/98). Warm water bottom fish were: Hippocampus ingens and Rhinobatos planiceps (82/83), Squatina armata (91/92); Umbrina xantii and Pseudopeneus grandisquamis (82/83; 97/98).

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