Interciencia ISSN: 0378-1844 [email protected] Asociación Interciencia Venezuela

Pavés, Héctor; Pequeño, Germán; Bertrán, Carlos; Vargas, Luis Limnetic feeding in (valenciennes, 1830) in the Valdivia River, Chile Interciencia, vol. 30, núm. 3, marzo, 2005, pp. 120-125 Asociación Interciencia Caracas, Venezuela

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HÉCTOR PAVÉS, GERMÁN PEQUEÑO, CARLOS BERTRÁN and LUIS VARGAS

leginops maclovinus, Va- throughout its entire ontogenetic develop- mens were measured for total length (TL, lenciennes, 1830 is a ment. live) and standard length (SL) using a monotypic species of the In the present study the ruler graduated in millimeters. Weights family Eleginopidae (Osteichthyes), sub- trophic relations between juveniles and were obtained using a field balance order . The species is adults of E. maclovinus within a limnetic graduated to 0.1g. At the laboratory, the thought to be of Antarctic evolutionary habitat, namely the upper Valdivia River fishes were initially fixed in 10% river origin, and is one of the most euryther- estuary, are compared. It was also tested water formalin for 48h and stored in 70% mic, euryhaline and stenobathic represen- whether E. maclovinus, the notothenioid ETOH. The stomachs were removed from tative of the suborder (Pequeño, 1989). species that most commonly inhabits each specimen and stored separately for This species is endemic to southern fresh waters, preys upon typical freshwa- subsequent contents analysis. Chile, southern Argentina and the Mal- ter species during its residence in this vinas Islands, where it occurs near oce- habitat, and remains carnivorous as ob- Collection of bottom samples anic beaches, and in large and small estu- served in specimens studied from brack- aries. In Chile it is found south of the ish and marine waters. Parasitological Sampling of the bottom Aconcagua River (33ºS) and has been evidence obtained from the stomachs of fauna of the Valdivia River was carried caught in rivers of southern Chile, several the fish is also used to evaluate the hy- out at two stations, including Las Mulatas kilometers offshore of the river mouths pothesis of carnivorous tendency in both and Los Pelúes (Figure 1). At each sta- (eg. Valdivia River, this study), and over juveniles and adults of this species. tion samples were obtained both near the 20km upstream in low salinity (limnetic) shore and at its deepest point, using cor- waters. Materials and Methods ers hand-held by divers. Four replicate Previous observations of samples were obtained at each sampling the trophic relations of E. maclovinus had Sample collection point. These samples were collected on been made on specimens obtained in ma- the same dates as the fishes were. rine and estuarine habitats. Although this Samples of E. maclovi- Macrofauna were ini- species has been generally considered as nus included 114 individuals obtained us- tially separated from the sediments using an omnivorous predator, the literature re- ing a 1.75×30m gillnet with 32mm open- a 0.5mm screen, fixed in 10% formalin, flects two contrasting variations on this ings. Catches were made from 17 to 20 and stored in 70% ETOH. These speci- point, the first by Guzmán and Cam- March 2002, at Las Mulatas (39º50'S, mens were subsequently separated under podónico (1973) and Gosztonyi (1979), 73º15'W), at a distance of about 16km a stereomicroscope and identified to the who postulated an ontogenetic change upstream from the Pacific Ocean, in the closest possible taxonomic species level from carnivorous behavior in early juve- Valdivia River estuary (Figure 1). Tidal using specialized keys. The species rich- nile stages to a herbivorous one in adults. movement in this estuary takes place to ness and relative abundance were deter- The second opinion, held by Pequeño about 20km inland of the river's mouth, mined on each of the samples (Morin, (1979) and Turner (1988) is that the spe- and limits of salt water (salinity= 0.1‰) 1999). The samples were finally dried at cies tended toward a carnivorous behavior reach about 14km inland. All the speci- 60ºC for 48h and weighed to determine

Keywords: / Eleginops / Eleginopidae / Feeding Shifts / Osmoregulation / / Received: 05/10/2004. Modified: 01/11/2005. Accepted: 02/04/2005.

Héctor Pavés. Marine Biologist and Doctoral Student, Universidad Austral de Chile (UACh). Germán Pequeño. Ph.D., Oregon State University, USA. Professor, Instituto de Zoología “Ernst F. Kilian”, Universidad Austral de Chile. Address: Casilla 567, Valdivia, Chile. e-mail: [email protected] Carlos Bertrán. M.Sc., UACh. Doctor, Universidad de Concepción, Chile. Professor, UACh. Luis Vargas. Marine Biologist, UACh. Doctoral Student, Universidad de Cadiz, Spain.

120 0378-1844/05/03/120-06 $ 3. 00/0 MAR 2005, VOL. 30 Nº 3 the approximate biomass per species in each sample.

Stomach contents analysis The determination of stomach contents was made using a ste- reomicroscope, aided by specialized taxonomic identification keys (Stuardo, 1961; Yamaguti, 1961; Menzies, 1962; Retamal, 1981), as well as with the aid from the specialists from the Institutes of Zoology and Botany at the Univer- sidad Austral de Chile. The individuals from the identified taxa were counted to obtain the frequency distributions of spe- cies and proportions of individual taxa in each analyzed stomach (F: frequency of occurrence per number of stomachs; F%: frequency of occurrence expressed in proportions of stomachs). The abun- dance of prey items found indicated the number of individuals of a given taxon registered in all the samples analyzed (N: abundance expressed per number of individuals; N%: abundance expressed in Figure 1. Geographic location of sampling stations, within the estuarine system of the percentage of individuals). Valdivia River, Chile. a: Las Mulatas, b: Los Pelúes.

Results of food items, accompanied by appre- fishes, mostly of estuarine or lacustrine ciable amounts of detritus such as sand origin. Of the analyzed stomachs, 96 A total of 114 speci- and rock grains (eg. schist, mica). Items (93%) contained remains, and 89 mens of E. maclovinus were obtained in observed included algae, plant material, (84%) contained plant remains (Table I). the samplings. These had a mean total gastropods, , insects, and The highest frequency group on the length (live) of 26.7cm (18-42cm, sd= 4.6cm) and a mean weight (live) of TABLE I 224.9g (75-800g, sd= 146.7g). Most FREQUENCY OF OCCURRENCE IN RELATION TO TOTAL NUMBER OF specimens were immature males of 2-4 STOMACHS ANALYZED (F, F%) AND NUMBER OF ITEMS (N, N%) IN THE years of age (Gosztonyi, 1974; Calvo, et STOMACH CONTENTS OF Eleginops maclovinus IN THE VALDIVIA RIVER al., 1992). The by-catch obtained in Taxa N N% F F% sampling for E. maclovinus included the salmoniformes Oncorhynchus mykiss Crustacea 96 93.20 (exotic, introduced), Galaxias maculatus () 59246 97.148 96 93.20 and G. platei, the smelts Austromenidia Tanaidacea () 104 0.171 14 13.59 laticlava and Basilichthys australis Ciprinidae (Ostracoda) 20 0.033 10 9.71 (Atherinopsidae), and the cosmopolitan Hemigrapsus crenulatum 5 0.008 5 4.85 Mugil cephalus (Mugilidae). Idotheinae (Valvifera) 3 0.005 3 2.91 Of all the E. maclovinus Zoea larvae 1 0.002 1 0.97 stomach samples, 103 (90%) could be Gastropoda 20 19.42 analyzed, while the remainder (11) were Littoridina comingii 20 0.033 19 18.45 in a degraded condition. The analyzed Bivalvia larvae 1 0.002 1 0.97 specimens had mean total length (fixed) Insecta 72 69.90 of 25.0cm (18-40.1cm, sd= 3.3cm) and Chironominae (Diptera:Chironomidae) 918 1.505 70 67.96 their mean standard length was 22.0 cm Hygrobatidae (Acarii) 2 0.003 2 1.94 (15.5-30.2cm, sd= 2.8cm). Trichoptera (Tubo) 2 0.003 2 1.94 Almost all the samples Inderminate 4 0.007 3 2.91 from which the complete digestive tract Teleostei 1 0.97 could be extracted (93%, n=96) had Inderminate 1 0.002 1 0.97 stomach contents present. In these it was Bryozoa 81 78.64 possible to identify species or high taxo- Indet. ovoid structures 519 0.851 57 55.34 nomic levels of plant and animal re- Filaments 44 42.72 mains. Only 7 (7%) of the stomachs Plants 48 46.60 were empty. A total of 55 (53%) stom- Scirpus californicus (Cyperaceae)* 139 0.228 29 28.16 achs analyzed contained nematode para- Inderminate 46 44.66 sites. The analysis of the TOTAL 60985 103 stomach contents revealed a broad range * Seeds

MAR 2005, VOL. 30 Nº 3 121 stomachs (F%) were the crustaceans (93.2%), followed by ramose bryozoans (78.64%), insects (69.9%), lake plants (46.6%), gastropods (19.42%) and, fi- nally, a bony fish (0.97%, Table I). In relation to the number of individuals per group (N%) the class Crustacea repre- sented 97%, followed by Insecta (1.5%) and bryozoans, lake plants, gastropods and Teleostei, each at proportions below 1% (Table I). A grand total of 98.9% (N, N%) of the items recorded in the stomachs were of animal origin, with less than 1.1% of plant origin.

Taxonomic analysis of the stomach contents by systematic group

Statistically significant differences were observed among the abundances (N) of the different food items analyzed (Kruskal-Wallis test: H(15, N=1599)= 949.94 p<0.01). The taxa showing the statistically greatest abundances were 1) the corophiid amphipods (mostly Para- corophium hartmannorum), 2) Diptera: Chironomidae, 3) bryozoans, and 4) lake plants (Multiple Comparison Kruskal- Wallis test, p<0.01). Each of the preced- Figure 2. Variation in the stomach contents of Eleginops maclovinus. a: common items, ing groups demonstrated absolute, el- b: less common items (lower occurrence and presence). evated abundances, and distinct tenden- cies among themselves (Table I). of 67.9%, making it the second most this material was difficult due to clump- 1) Class Crustacea: In this group the common item eaten by the fish. Also ing, but undoubtedly represented a fre- main taxon in numerical abundance identified were trichopteran tubes and a quent item in the stomachs of E. (N%) as well as in frequency of occur- hygrobatid mite, representing less than maclovinus. 1% in abundance and 1.9% in frequency rence in stomachs (F%) was shown by 6) Lacustrine plants: 46.6% of the of occurrence. the lacustrine amphipod stomachs contained remains of lake hartmannorum, which represented 4) Subdivision Teleostei: Only one indi- plants, including both vegetal portions 97% of the individual prey species, vidual was recorded, and this was in an and seeds: the latter were determined and was found in 93.2% of the stom- advanced stage of digestion, remaining to be seeds of Scirpus californicus achs analyzed (Table I). Other crusta- unidentified. This represented less than (Cyperaceae) and had a frequency of oc- cean items included Tanaidacea (Ma- 1% in frequency of occurrence and currence of 28.1% and an abundance of lacostraca), Ciprinidae (Ostracoda), abundance among the items analyzed. less than 1% (Table I; Ramírez et al., Hemigrapsus crenulatus (Decapoda), 1976). and Idotheinae (Isopoda, Valvifera) 5) Ramose invertebrates: Due to their which as a group represented less than advanced state of digestion, specific 7) Nematode parasites (Table II): The 1% of the total individuals counted. identification of this material was im- main nematode parasite in the stomachs The tanaids, ciprinids, and H. crenu- possible, although its tubular structure, of the fish was Ascarophis sp. (Cystido- latus gave frequencies of occurrence of dichotomous ramification and presence colidae), with both mature males and fe- between 2.9 and 13.5%. Finally, a bra- of ovoidal structures in the external males present. This nematode had a fre- chyuran zoea larva was encountered, walls suggested it to be assigned to quency of 44.6% and an abundance of representing less than 1% both in abun- “bryozoa”. These remains were found in 75.7% (n= 87), and was the most nu- dance and frequency. 78.64% of the stomachs, but with an merous of the helminths identified. Also abundance near 1%. Quantification of identified from the stomachs were ma- 2) Class Mollusca: Only one species of gastropod, Littorina cumingii, was re- corded, which had a frequency of occur- TABLE II rence of near 18.4%, and an abundance FREQUENCY OF OCURRENCE (F, F%) AND NUMBER OF PARASITE of less than 1%. A few bivalve veliger NEMATODS (N, N%) IDENTIFIED WITHIN THE STOMACH CONTENTS larvae were also observed. OF Eleginops maclovinus IN THE VALDIVIA RIVER 3) Class Insecta: The most important Parasites N N(%) F F (%) taxon of this group were Diptera of the Ascarophis spp. (Cystidicolidae) 87 75.7 46 68.7 family Chironomidae, with an abundance Anisakids 28 24.3 21 31.3 of 1.5%, and a frequency of occurrence Total 115 100 67 100

122 MAR 2005, VOL. 30 Nº 3 ture anisakids, at a frequency of 20.3%. TABLE III This group included 15 larvae and 13 ABUNDANCE AND BIOMASS OF MACROBENTHOS SPECIES IN SECTORS* adults. OF LOS PELÚES AND LAS MULATAS AT THE VALDIVIA RIVER

Analysis by size of fish Los Pelúes margin Los Pelúes center Taxa Abundance / Biomass Abundance / Biomass When the fish samples m2 (gr/m2)m2 (gr/m2) were separated into size ranges of 1cm, Prionospio sp. 63.14 0.006 357.77 0.08 to give 13 ranges between 15 and 30cm Perinereis gualpensis 168.36 0.59 631.36 1.30 TL, no statistically significant differences Paracorophium hartmanorum 841.81 0.07 2209.75 0.27 were observed in total species abundance Tubifex sp. 168.36 0.010 21.04 0.002 in stomachs from the different size groups (Kruskal-Wallis test H(12, N= Las Mulatas margin Las Mulatas center 1599)= 19.21559, p>0.05). However, a Prionospio sp. 105.23 0.019 3556.65 0.85 decrease in abundance of the Coro- Perinereis gualpensis 526.13 0.73 1452.12 1.85 phiidae, lacustrine plants (S. californicus), Paracorophium hartmanorum 2336.02 0.24 589.27 0.06 bryozoan remains, Chironomidae, and Os- Trichoptera 21.04 0.09 0 0 tracoda was observed as total length of Chironomidae 21.04 0.006 0 0 the fishes increased (Figures 2a, b). In * The sectors are differentiated according to sampling locations, margin or center. contrast, the Idotheidae, H. crenulatus, one teleost, and L. cumingii were re- corded in specimens over 19cm SL, and increasing in the larger E. maclovinus corophium hartmannorum, somewhat negatively selected by the fish, based on (Figure 2b). similar to that recorded by Pequeño its feeding behavior which includes With the nematode para- (1979). It should be noted that Pequeño grazing over sand or gravel, not appear- sites, greater numbers of anisakids were (1979) considered specimens between ing to consume species which are in found in the smaller fish specimens, con- 280 and 880mm TL, to be inhabitants of lime-clay sediments containing decom- trary to the numbers of ascarophites marine or mixohaline habitats. In the posing organic material as typical of which were more common in the larger present study samples obtained were be- Prionospio sp. and P. gualpensis. This fishes. tween 180 and 400mm TL, and distrib- situation would reflect a selective behav- uted in areas of strong limnetic affinity ior toward species which inhabit gravel Comparison of the fish stomach and low salinity (Valdivia River surface and sandy areas, or in association with contents and river fauna salinity= 0‰, bottom salinity= 5‰; small filamentous algae where benthic Wladimir Steffen, personal communica- grazing behavior is possible (eg. Tri- Items found in the E. tion). choptera, Chironomidae, and P. hartman- maclovinus stomachs were common at The Las Mulatas station norum). The fish may be an opportunis- both stations sampled in the Valdivia is at the limit of effect of the estuarine tic predator (Morin, 1999) since it ex- River, including P. hartmannorum, salt wedge in the Valdivia River estuary, ploits the resource in major abundance Chironomidae, and Trichoptera. (Tables with freshwater occurring to the head of in the environment (eg. P. hartman- II, III). There was, however, variation in the estuary, and tidal motion noted up to norum). abundance and diversity of the four taxa 20km inland from the mouth of the estu- The remains assigned to in relation to the sampling depth in the ary (Pers. Comm. Wladimir Steffen). bryozoa and lacustrine plants observed river (shore vs. depth). Amphipods were The majority of samples of E. in the stomach contents of E. maclovinus more abundant in shore samples at Las maclovinus having stomach contents probably represent items accidentally Mulatas. In mid-river, the polychaetes (93%), the low degree of digestion of consumed during feeding on crustaceans Prionospio sp. and P. gualpensis were the prey, and the similarities between and/or insects due to the common be- more abundant, although they were not species ingested and those recorded havior such as the amphi- recovered from the stomach contents of from the environment, allow the assump- pods, isopods and insects in seeking ref- the fish. Lower abundance and biomass tion that Las Mulatas is a feeding area uge in filamentous microhabitats such as were found at Los Pelúes than at Las used by the fishes to exploit resources algae and other plants, reducing predator Mulatas, where the oligochaete Tubifex located near the rivers edge (Table I, pressure and indirectly increasing the sp. inhabited anoxic bottoms rich in or- III). food offering of the substrate (Schneider ganic matter. This species was not re- Various species of poly- and Mann 1991a, b; Peñaloza, 1993). covered from fish stomachs. Thus, some chaetes, including Perinereis gualpensis Another aspect suggesting the accidental of the potential preys are not used by and Prionospio sp. were found in the nature of consumption of the bryozoans the fishes. sediment, but not among the stomach was the low degree of digestion of this contents although other investigators re- material in the fish stomachs. The same Discussion corded the presence of polychaete re- occurred for Scirpus californicus, where mains as well as remains of the oli- accidental ingestion of the seeds may be Among the large variety gochaete Tubifex sp. (Ruiz, 1993). This related to sedimentary grazing on animal of food items present in the stomach situation may be explained by the life prey, particularly the chironomids. The contents of E. maclovinus we found re- style of these annelids (buried, as accidental consumption of seeds may mains of algae, land plants, crustaceans, endofauna), and with soft body struc- lead to probable “ichthyochoria” or seed insects, mollusks and fishes. tures which are easily digested, imped- dispersal by fishes as found in the Ama- The item with the high- ing their identification in the stomachs. zon by Gottsberger (1978). This was est frequency of occurrence was Para- Another possibility is that they may be also noted by Guzmán and Campodónico

MAR 2005, VOL. 30 Nº 3 123 (1973) who reported seeds of graminea and other studies included Enteromor- the present study shows its capacity to in E. maclovinus stomach contents. pha, Porphyra, and Ulva which are spe- feed in limnetic habitats as part of its The crustaceans, in- cies which typically harbor crustaceans capacity for survival in freshwater. The sects, and plants observed in the stom- and show little sign of digestion in the reduced number of species found in the ach contents in this study, have only digestive tract of the fishes, which fish stomachs in the limnetic habitat been reported from limnetic or estua- makes it doubtful that they serve as an (14 items, present study) is a reflection rine environments (see Stuardo, 1961; energy source (Isla and San Román, of the reduced species diversity of the Ramírez et al., 1976; Pequeño, 1979; 1995). However, it is difficult to say at freshwater habitat compared with those Artigas et al., 1985; Jaramillo et al., what point microscopic algae, generally of the estuary (Beagle Channel, 24 1985; Bertrán, 1989; Ruiz, 1993). This present in the surface of other organ- items; Isla and San Román, 1995) and suggested that the fishes sampled had isms, may play a role in fish nutrition. marine habitats (Mehuín, 35 items; not migrated into brackish (Corral Bay, Pequeño (1979), Aceve- Pequeño, 1979). This aspect is related 9.2‰ surface, 33.7‰ bottom salinity) do (1994), Ruiz (1993) and Isla and to the selectivity of the predator and or marine areas to feed, but rather con- San Román (1995) determined that E. lower diversity of prey in inner beaches sumed prey from freshwater, upper maclovinus was predominantly feeding of the estuary compared with the mouth reaches of the river (0‰). This capacity on crustaceans, since amphipods, iso- of the estuary of the Valdivia River for tolerating low salinity and feeding pods, cumaceans, and decapods were (Low, 1993; García and Ojeda, 1995), on limnetic species explains catches of the most abundant prey found in indi- together with the general tendency to- these fishes to more than 21km inland viduals from 61 to 240mm TL and wards lower species diversity in estuar- from the mouth of the Valdivia River. from 180 to 700mm TL. ies than in seas or lakes (Kiely, 1999). This aspect is corroborated by the lim- Although the results of It was of interest that netic fish fauna associated with the ar- the present study concur with those of mature nematodes of the Ascaro- eas from which present samples were Guzmán and Campodónico (1973) in phis occurred in E. maclovinus, since obtained, such as Austromenidia laticla- relation to the predominance of car- this fish had not been considered as a via, Basilichthys australis, Oncorhyn- nivorous feeding in E. maclovinus, definitive host for this nematode (Muñoz chus mykiss, Mugil cephalus, Galaxias those authors maintained that individu- and George-Nascimento, 2002). Our maculatus, G. platei, Cheirodon sp. als of this species greater than 160mm records indicate that infection by these (Ruiz, 1993; Vila et al., 1999). Of these SL were basically herbivorous. They parasites (anisakids and Ascarophis sp.) only M. cephalus is capable of life both mentioned that individuals from 160 to occurred in E. maclovinus at sizes less in the sea and in freshwater (Ruiz, 410mm SL fed predominantly on algae, than 150mm SL, both in limnetic and 1993). which had a frequency of occurrence of estuarine systems. This point was not It has been recognized 94% and occupied approximately 83.4% mentioned in the review of Marcogliese that freshwater fishes have a diet simi- of the volume of the stomachs. (2002) although reported by Muñoz and lar to that of E. maclovinus in this The present study, al- George-Nascimento (2002). study in these habitats. Thus Oncorhyn- though showing a frequency of occur- Another parasite, Cys- chus mykiss and Cauque mauleanum rence of plant material of 86.7%, tidicola sp. (fam. Thelaziidae), was feed principally on chironomid larvae showed an abundance of significantly identified from E. maclovinus stomachs and pupae, Littorinidae, Trichopteridae, less than 1% which was markedly dif- by Szidat (1950). This parasite is only Acarii, and Amphipoda (Artigas et al., ferent than that observed by Guzmán known from freshwater habitats where 1985; Klink and Eckmann, 1985). and Campodónico (1973). This sug- it infects intermediate and definitive The data showing that gested carnivorous behavior in the size hosts, in contrast to Ascarophis sp. as the fishes grew in size and weight, classes studied from the Valdivia River, which are found in hosts in both estua- corophiid crustaceans (P. hartman- which may be a tendency maintained rine and limnetic habitats (Ronald, norum) significantly decreased in the over time in accordance with the stabil- 1986). Identification of Cystidicola sp. stomach contents, as also found with ity of food resources (Acevedo, 1994). in this study demonstrates that these the ostracods, suggested a succession of Gosztonyi (1979), simi- fishes were feeding on freshwater crus- species taken by E. maclovinus with in- larly to Guzmán and Campodónico taceans. crease in size, where smaller prey items (1973) suggested that the E. maclovinus Marcogliese (2002) are progressively replaced by larger studied was an omnivorous species with suggested that the definitive host for ones. In spite of these changes in pre- clear tendencies towards consumption this species could be fishes, birds, or dation, the fish was observed to be of plant material in all stages of its de- mammals, with the intermediate hosts more of a carnivore than herbivore, in velopment. However, he did not present being mainly crustaceans, particularly agreement with Pequeño (1979), Turner evidence for digestion of the plant ma- decapods of the genera Pagurus or (1988), Acevedo (1994), and Isla and terial placing doubts on its value as an Carcinus. Fagerholm and Butterworth San Román (1995) and differing from energetic input. Gosztonyi's (1979) ob- (1988) previously indicated that both the hypothesis of Guzmán and Cam- servations have also been noted by larvae and some adult stages of podónico (1973). Pequeño (1979) and other authors. According to him fila- Ascarophis sp. were isolated from deca- Acevedo (1994) recorded that in indi- mentous structures such as the form of pods, isopods, and mainly amphipods of viduals of 240-280mm TL from marine some bryozoans, provide refuge for 18-20mm in TL in marine and estuarine and mixohaline environments 84% of crustaceans, and as presently suggested environments. The preceding two re- the food items were of animal origin there is no evidence that the fish is a ports suggest that the intermediate hosts (e.g. crustaceans, ) and over primary consumer. of Ascarophis sp. in the Valdivia River 11% of plant origin, increasing in the In addition to previous may be Hemigrapsus crenulatus or present study to 98.9% animal, and studies concerning the broad scope of Paracorophium hartmannorum based on >1% plant remains. Algal remains cited feeding of E. maclovinus (Pequeño, their high frequency of occurrence in by Pequeño (1979) and Acevedo (1994) 1979; Turner, 1988; Acevedo, 1994), the fish stomach contents, which merits

124 MAR 2005, VOL. 30 Nº 3 Menzies RJ (1962) The zoogeography, ecology future study. The preceding indirectly REFERENCES confirms our observations on the occur- and systematics of the Chilean marine iso- Acevedo A (1994) Comparación de la alimen- pods. En Chile Exped. 1948-49. Reps. Lund rence of carnivorous feeding in Ele- Univ., Sweden. 162 pp. ginops maclovinus in the Valdivia River. tación de Eleginops maclovinus (Valen- ciennes, 1830) en base a muestreos de 1974 Morin PJ (1999) Community Ecology. Black- Marcogliese (2002) suggested that y 1991 para la zona de Mehuin, Chile. (Te- well. Malden, MA, USA. 424 pp. Ascarophis sp. (Cystidicolidae) had leostomi, Nototheniidae). Tesis. Facultad de gadiform fishes as definitive hosts, and Ciencias, Universidad Austral de Chile. Muñoz G, George-Nascimento M (2002) ¿Hay Valdivia, Chile. 35 pp. más de una especie de Ascarophis (Inema- this type of result should be tested in toda: Cystidicolidae) en los peces de la E. maclovinus because it is a perciform Artigas J, Campusano E, González U (1985) costa chilena? Resúmenes XIX Congreso de fish (Eleginopsidae: Notothenioidae, Contribución al conocimiento de la biología Ciencias del Mar, 1999. Universidad de y hábitos alimentarios de Salmo gairdneri Antofagasta, Chile. p. 148. this study; Muñoz and George-Nasci- (Richardson, 1836) en lago Laja (Chile). mento, 2002). The parasitological re- Gayana Zool. 4: 3-29. Pequeño G (1979) Antecedentes alimentarios de Eleginops maclovinus (Valenciennes, 1830) search needs to be broadened by ex- Bertrán C (1989) Zonación y dinámica temporal (Teleostomi: Nototheniidae) en Mehuín, tending the range of the area consid- de la macroinfauna intermareal en el estua- Chile. Acta Zool. Lilloana 35: 207-230. ered and using larger sample numbers rio del Río Lingue (Valdivia, Chile). Rev. and a broad range of sizes, as well as Chil. Hist. Nat. 62: 19-32. Pequeño G (1989) The geographical distribution Calvo J, Morriconi E, Rae G, San Román N and taxonomical arrangement of South- extending the parasitological analyses american nototheniid fishes (Pisces: and obtaining more information on the (1992) Evidence of protandry in subantarctic notothenid, Eleginops maclovinus (Cuv. & Osteichthyes). Bol. Soc. Biol. Concepción food species availability. All this with Val., 1830) from the Beagle Channel, Argen- 60: 183-200. the object of better understanding the tina. J. Fish Biol. 40: 157-164. Peñaloza C (1993) Distribución de la epifauna ontogenetic variation and trophic behav- Fagerholm H, Butterworth E (1988) Ascarophis sobre Gracilaria chilensis Bird, McLachlan ior of E. maclovinus within a referen- sp. (Nematoda: Spirurida) attaining sexual & Oliveia (Rhodophyta, Gigartinales) en el tial framework which may provide new maturity in Gammarus spp. (Crustacea). estuario del Río Maullín, X Región, Chile. light on the biological and phylogenetic Syst. Parasitol. 12: 123-139. Tesis. Universidad Austral de Chile. 63 pp. history of the suborder Notothenoidei. García V, Ojeda C (1995) Estructura del bentos Ramírez C, Romero M, Riveros M (1976) Lista The present results sup- en áreas con enriquecimiento orgánico en el de cormófitos acuáticos de la región val- complejo estuarial de los ríos Calle-calle, diviana. Bol. Mus. Nac. Hist. Nat. Chile 22: port our initial hypothetical idea, stated Valdivia y Cruces. Tesis. Facultad de Cien- 3-12. in the Introduction, that E. maclovinus cias, Universidad Austral de Chile. Valdivia, Chile. 30 pp Retamal M (1981) Catálogo Ilustrado de los living in fresh waters has to eat fresh- Crustáceos Decápodos de Chile. Gayana, water organisms, despite the fact that Gosztonyi A (1974) Edad y crecimiento del Zool. 44: 1-110. the species is well known as a marine “Róbalo” Eleginops maclovinus (Osteich- thyes, Nototheniidae) en aguas de la ría Ronald C (1986) A preliminary review of the fish. The present study also opens pos- Deseado y sus adyacencias. Physis 33: 1-8. genus Ascarophis van Beneden, 1871 sibilities to the hypothesis that this spe- (Nematoda: Cystidicolidae) of the gas- cies lives in freshwater for extended pe- Gosztonyi A (1979) Biología del “róbalo” Elegi- trointestinal tract of fishes. Department of nops maclovinus (Cuv. & Val., 1830). Tesis. Zoology, University of Hong Kong. 54 pp. riods of time, without needing marine Facultad de Ciencias Exactas y Naturales, salinity for survival. This behavior, to Universidad Nacional de Buenos Aires, Ar- Ruiz V (1993) Ictiofauna del Río Andalién some extent, contributes to the idea that gentina. 129 pp. (Concepción, Chile). Gayana Zool. 57: 109- this species is probably one of the old- Gottsberger G (1978) Seed dispersal by fish in 278. est living species of notothenioid, the inundated regions of Humaita, Schneider F, Mann K (1991a) Species specific which, due to its Antarctic origin, must Amazonia. Biotropica 10: 170-183. relationships of invertebrates to vegetation in a seagrass bed. I Correlational Studies. J. have been initiated by individuals ca- Guzmán L, Campodónico I (1973) Algunos as- pectos de la biología de Eleginops maclovi- Exp. Mar. Biol. Ecol. 145: 101-117. pable of living in areas with permanent nus (Cuv. y Val.) 1830, con especial re- Schneider F, Mann K (1991b) Species specific melting of ice, at very low salinities. ferencia a su morfometría, caracteres merís- relationships of invertebrates to vegetation ticos y alimentación. An. Inst. Patagonia 4: in a seagrass bed. II Experiment on the im- 343-371. ACKNOWLEDGEMENTS portance of macrophyte shape epiphyte Isla M, San Román N (1995) Alimentación de cover and predation. J. Exp. Mar. Biol. The authors express Eleginops maclovinus (Pisces, Nototheniidae) Ecol. 145: 119-139. en el Canal Beagle, Argentina. Naturalia Stuardo J (1961) Contribución a un Catálogo de their gratitude to León Matamala for Patagonica 3: 107-127. laboratory assistance at the Institute of los Moluscos Gasterópodos Chilenos de Jaramillo E, Mulsow S, Navarro R (1985) Inter- Agua Dulce. Gayana Zool. 1: 7-32. Zoology, Universidad Austral de Chile tidal and subtidal macroinfauna in the (UACh). For their assistance in the Queule River Estuary, South of Chile. Rev. Szidat L (1950) Los parásitos del róbalo (Elegi- Chil. Hist. Nat. 58: 127-137. nops maclovinus Cuv. & Val.). I Congr. identification of specimens, to Carlos Nac. Pesquero Marítimo e Ind. Derivadas. Jara, Maritza Mercado, Alejandro Bravo Kiely G (1999) Ingeniería Ambiental. Fundamen- Mar del Plata, Argentina. pp. 234-270. and Wladimir Steffen at the Institute of tos, entornos, tecnologías y sistemas de ges- tión. McGraw Hill. Madrid, España, 1331 pp. Turner A (1988) Relaciones tróficas de dos es- Zoology; to Jorge Jaramillo, Carlos pecies bentófagas, Cauque mauleanum Ramírez and Miguel Álvarez at the In- Klink A, Eckmann R (1985) Age and Growth, Feeding Habits, and Reproduction of Cauque (Steindachner, 1902) y Eleginops stitute of Botany; to M. Teresa Gon- mauleanum Steindachner 1896 (Pisces: maclovinus (Valenciennes, 1830) (Pisces: zález and Daniel Ekblaw, Doctoral Pro- Atherinidae) in Southern Chile. Stud. Neotr. Osteichthyes) en el estuario del río Queule (IX Región, Chile) Fauna and Env. 2: 239-249. . Tesis. Facultad de gram in Sciences, all from UACh; and Ciencias, Universidad Austral de Chile. to M. Eliana Ramírez and Melica Low A (1993) Distribución y estructura de la Valdivia, Chile. 48 pp. Muñoz Schick, Botany Section, Na- pequeña macroinfauna estival en estuarios Vila I, Fuentes L, Contreras M (1999) Peces tional Museum of Natural History, micromareales del sur de Chile. Tesis. Facultad de Ciencias, Universidad Austral de límnicos de Chile. Bol. Mus. Nac. Hist. Nat. Santiago, Chile. This study is part of Chile. Valdivia, Chile. 53 pp. Chile 48: 61-75. Project S-200223 of the Division of Re- Marcogliese D (2002) Food webs and the trans- Yamaguti S (1961) Sistema Helminthum. Vol. III. search and Development, UACh, Val- mission of parasites to marine fish. Parasi- The nematods of vertebrates. Part I- II. divia, Chile. tology 124: S83-S99. Interscience. New York, USA. 1135 pp.

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