Diet,trophic interactions and possible ecological role of commercial sharks and batoids in northern Peruvian waters

The Peruvian sea represents one of the most productive ocean ecosystems and possesses one of the largest elasmobranch fisheries in the Pacific Ocean. Ecosystem-based management of these fisheries will require information on the trophic ecology of elasmobranchs. This study aimed to understand the diet, trophic interactions and the role of nine commercial elasmobranch species in northern Peru through the analysis of stomach contents. A total of 865 non-empty stomachs were analysed. Off northern Peru, elasmobranchs function as upper-trophic-level species consuming 78 prey items, predominantly teleosts and cephalopods. Two distinctive trophic assemblages were identified: (a) sharks (smooth hammerhead shark Sphyrna zygaena, thresher shark Alopias spp. and blue shark Prionace glauca) that feed mainly on cephalopods in the pelagic ecosystem; and (b) sharks and batoids (Chilean eagle ray Myliobatis chilensis, humpback smooth-hound Mustelus whitneyi, spotted houndshark Triakis maculata, Pacific guitarfish Pseudobatos planiceps, copper shark Carcharhinus brachyurus and school shark Galeorhinus galeus) that feed mainly on teleosts and invertebrates in the benthonic and pelagic coastal ecosystem. This study reveals for the first time the diet of T. maculata and the importance of elasmobranchs as predators of abundant and commercial species (i.e., jumbo squid Dosidicus gigas and Peruvian anchovy Engraulis ringens). The results of this study can assist in the design of an ecosystem-based management for the northern Peruvian sea and the conservation of these highly exploited, threatened or poorly understood group of predators in one of the most productive marine ecosystems.     

First assessment of the diet composition and trophic level of an assemblage of poorly known chondrichthyans off the central coast of Peru

Although chondrichthyans are conspicuously present in shallow waters, many ecological aspects of neritic species in the Humboldt Current System remain unknown. This study provides a first assessment of the diet of seven commercially exploited and understudied sympatric chondrichthyans inhabiting nearshore habitats off the central coast of Peru: four stingrays (Hypanus dipterurus, Myliobatis peruvianus, M. chilensis, and Urotrygon chilensis), a guitarfish (Pseudobatos planiceps), a smooth-hound shark (Mustelus mento), and a chimaera (Callorhinchus callorynchus). A total of 166 stomachs were examined between 2012 and 2015 and prey items were pooled for the total of years for analysis. Although our analysis did not account for inter seasons variability, our results suggest diet partitioning among species, except for the stingrays’ group. A diet based on soft-bottom polychaetes and fish was shared by H. dipterurus, M. peruvianus, and M. chilensis, while soft-bottom polychaetes and crabs were more important in U. chilensis. The smooth-hound shark and guitarfish exhibited a diet dominated by crabs, and the chimaera consumed mainly hard-bottom mollusks. Foraging habitat estimations distinguished two main habitats of association: Benthic, including the stingray U. chilensis, the chimaera, and the smooth-hound shark; and benthic-demersal, including the guitarfish, and the rest of stingrays. A pattern of feeding specialization was observed for H. dipterurus, P. planiceps, and C. callorynchus. Preliminary trophic level estimations based on diet composition placed these species as secondary consumers. Intraspecific dietary variation was assessed for P. planiceps and H. dipterurus as their sampled sizes allowed meaningful comparisons. The diet of P. planiceps varied from small to large sizes but not for H. dipterurus. No differences were detected on diet composition between males and females in either species. Despite the limited temporal resolution, this study provides the first insights of chondrichthyans predatory activity, suggesting diet partitioning among the species of this assemblage in a nearshore habitat of the central coast of Peru. Enhancing the temporal resolution of this type of studies would improve our knowledge on trophic functioning in the Humboldt Current ecosystem.     

Weight–length relationships of six batoids in the Ecuadorian Pacific

Weight–length relationships (WLR) were estimated for six batoids, namely: Urotrygon chilensis, Narcine entemedor, Rhinobatos leucorhynchus, Rhinobatos planiceps, Rhinobatos prahli and Urobatis tumbesensis captured in the Ecuadorian Pacific. Data were collected between October 2013 and August 2014 in two artisanal fishing ports. In addition, this represents the first WLR estimations for five of the species.     

Diet of the Chilean sandperch, Pinguipes chilensis (Perciformes, Pinguipedidae) in southern Chile

A study of the Pinguipes chilensis Valenciennes 1833 diet was carried out on 414 specimens captured on the Talcahuano, Chile coastline (36°41′S; 73°06′E) between October 1998 and March 2000. P. chilensis, endemic to the southeast Pacific (from Tumbes, Peru to Magallanes, Chile), is confirmed as a general predator over a wide trophic spectrum including 61 taxa. Crustaceans (mostly mysids, but also a wide variety of decapods) made up the principal dietary component, followed by fish and annelids. Prey belonging to Mollusca, Ophiuroidea, Echinoidea, Rhynchocoela, Sipunculida, Echiura and Urochordata were also present. There were no significant differences between male and female diets, although they shared only 32 prey. A significant dietary difference was found, however, between analysed size groups: specimens under 30 cm total length (TL) preyed mainly on the amphipod, Ampelisca araucana; those over 30 cm TL preyed on the mysid, Neomysis sp.; and those over 40 cm TL on fish, annelids, molluscs and echinoderms. Seasonal differences, due in large part to the dynamics of the prey species, were also found to be significant. Crustaceans were the predominant prey throughout the study with the exception of autumn, when fish were the most common prey.     

Climatic signals in growth and its relation to ENSO events of two Prosopis species following a latitudinal gradient in South America

Semiarid environments throughout the world have lost a major part of their woody vegetation and biodiversity due to the effects of wood cutting, cattle grazing and subsistence agriculture. The resulting state is typically used for cattle production, but the productivity of these systems is often very low, and erosion of the unprotected soil is a common problem. Such dry‐land degradation is of great international concern, not only because the resulting state is hardly productive but also because it paves the way to desertification. The natural distribution of the genus Prosopis includes arid and semiarid zones of the Americas, Africa and Asia, but the majority of the Prosopis species are, however, native to the Americas. In order to assess a likely gradient in the response of tree species to precipitation, temperature and their connection to El Niño southern oscillation (ENSO) events, two Prosopis species were chosen along a latitudinal gradient in Latin America, from northern Peru to central Chile: Prosopis pallida from a semi‐arid land in northern and southern Peru and P. chilensis from a semiarid land in central Chile. Growth rings of each species were crossdated at each sampling site using classical dendrochronological techniques. Chronologies were related with instrumental climatic records in each site, as well as with SOI and N34 series. Cross‐correlation, spectral and wavelet analysis techniques were used to assess the relation of growth with precipitation and temperature. Despite the long distance among sites, the two Prosopis species presented similar responses. Thus, the two species' growth is positively correlated to precipitation, while with temperature it is not. In northern Peru, precipitation and growth of P. pallida present a similar cyclic pattern, with a period of around 3 years. On the other hand, P. pallida in southern Peru, and P. chilensis also present this cyclic pattern, but also another one with lower frequency, coinciding with the pattern of precipitation. Both cycles are within the range of the ENSO band.     

Trophic ecology of yellownose skate Zearaja chilensis,a top predator in the south‐western Atlantic Ocean

The diet and trophic level (T_L) of the yellownose skate Zearaja chilensis in the south‐western Atlantic Ocean (35°–54° S), and how these varied in relation to body size, sex, maturity stage, depth and region were determined by analysis of stomach contents. From 776 specimens analysed, 671 (86·5%) ranging from 180 to 1190 mm total length (L_T) had prey in their stomachs. The diet was dominated by fishes, mainly the notothenioid Patagonotothen ramsayi and the Argentine hake Merluccius hubbsi. The consumption of fishes and crabs increased with increasing predator size, and these preys were more important in the north than in the south. Isopods and other crustaceans were consumed more in the south and their consumption decreased as the size of Z. chilensis increased. The T_L of Z. chilensis increased with L_T from 4·29 to 4·59 (mean 4·53), confirming their ecological role as a top predator. The small and large size classes exhibited a low diet overlap and the highest spatial segregation, whereas medium and large specimens had higher co‐occurrence and dietary overlap indices. A clear distinction in tooth shape was noted between sexes in adult specimens, with males having longer cusps. This sexual heterodonty may be related to reproductive behaviour, increasing the grasping ability of males during courtship, because there were no differences in diet between the sexes.     

Insights into marine otter (Lontra felina) distribution along the Peru coastline

The marine otter (Lontra felina) has a patchy distribution associated with rocky coastlines along the Pacific coast of South America. In Peru marine otters are found from La Libertad (8°04′S) to Tacna (18°09′S), however, few studies have assessed its population and conservation status. To assess marine otters' current distribution along the Peru coastline, we conducted visual surveys and collected environmental characteristics such as human presence and habitat type. We surveyed 20 locations from five regions where otter presence was based on signs of detection (spraints, food leftovers, tracks, or direct observations). In addition, data on human presence, habitat type, and geographic location were also collected. Across the 20 locations, 268 sections were scanned, and marine otters were detected in 90% (n = 18) of locations and in 19% (n = 52) of sections. Spraints were the most frequent sign detected while direct observations occurred only in seven locations. Our analysis indicates habitat features play an important role in marine otter presence, with habitats with large rocks providing preferred conditions. Our study provides information on marine otter distribution along the Peru coastline that can assist in the identification of locations for focused conservation initiatives and strategies, which should be coordinated among regions to strengthen their design and implementation.     

“El Niño” events recorded in dry-forest species of the lowlands of northwest Peru

The northwest coast of Peru (5°S, 80°W) is very sensitive to and impacted by the climate phenomenon El Niño-Southern Oscillation (ENSO). Though mainly desert, this warm, dry region contains an equatorial dry forest. We report the first dendrochronological studies from this region and identify several species that have dendrochronological potential. Short ring-width chronologies of Palo Santo (Bursera graveolens) show a well-developed response to the ENSO signal over the last 50 years and good inter-site correlations. Preliminary isotopic studies in Algarrobo (Prosopis sp.) also show evidence of the 1997–98 El Niño event. ENSO events have a strong effect on the variability in the growth of several species and thereby on the economy of rural communities where the wood is used for housing, cooking, furniture, tools, fodder and medicinal uses. The extensive use of wood in archeological sites also offers the possibility of ultimately developing longer records for some of these species.     

Analysis of the potential geographic range of the Pacific oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis> (Thunberg, 1793) based on surface seawater temperature satellite data and climate charts: the coast of South America as a study case

Ecological niche modeling based on surface seawater (SST) and atmospheric (AT) temperature records was used to predict the potential range of distribution of Crassostrea gigas, focusing on the South American coast as a study case. In its native range, the species maintains self-sustaining populations at thermal regimes with mean SST ranging from 14.0° to 28.9°C for the warmest month and from −1.9° to 19.8°C for the coldest month of the year. Settlement is also constrained to mean AT varying between 15° and 31°C for the warmest month and between −23° and 14°C for the coldest month of the year. Latitudinal limits for the species’ distribution in South America predicted by the analysis of AT regimes were Valdivia-Chiloe Island (39.8o–42.0°S, Chile) and Pisco (13.4°S, Peru) on the Pacific coast, and San Julian port (49.3°S) (Argentina) and Garopaba-Rio Grande (28.0°–32.0°S, Brazil) on the Atlantic coast. Geographical limits of distribution predicted by analysis of SST regimes were Chiloe Island (42.0°S, Chile) and Mancora (4.1°S, Peru) on the Pacific coast, and Puerto Deseado ria (47.7°S, Argentina) and Paranaguá (25.7°S, Brazil) on the Atlantic coast. Therefore, SST regimes would expand the potential range on the Pacific coast equatorward relative to AT.     

Exploring nursery sites for oviparous chondrichthyans in the Southwest Atlantic (36°S–41°S)

The aim of this paper was to explore egg-laying areas of oviparous chondrichthyans occurring in the northern part of the Southwest Atlantic Ocean (36°S–41°S) at between 50 and 200 metres depth and the Mar del Plata Canyon (from 200 to 3447?m). A total of 515 capsules were collected corresponding to 10 species. Four species accounted for 87.6% of the total catch: Psammobatis normani, Bathyraja macloviana, Amblyraja doellojuradoi and Bathyraja brachyurops. The remaining corresponded to Schroederichthys bivius, Psammobatis rudis, Zearaja chilensis, Bathyraja albomaculata, Psammobatis lentiginosa and Bathyraja sp. Most hauls were monospecific and relatively few hauls contained four or five species (southern part of the area, in sites located at 75 and 94–105?m depth). No egg capsules were recorded between 1712?m and 3447?m. Highest densities (>3000 capsules/km²) were mainly found between 39°46.2′ and 40°29.9′S from 85 to 105?m and they were also recorded near the Mar del Plata Canyon at 37°59.7′S and at 852?m. The highest value recorded was 12,326 capsules/km² (located at 40°18.9′S and 85.4?m). The highest densities for each of the most abundant species are discussed. The finding of high densities of egg cases near the Argentine shelf-break front indicates that many skate species use this area as a nursery site. The egg-laying areas explored here are the first reported sites of this kind in the Southwest Atlantic Ocean. Recognizing and protecting egg-laying habitats may be important steps to a long-term conservation of oviparous chondrichthyan populations.     

The distribution of the ectoparasite fauna of Sebastes capensis from the southern hemisphere does not correspond with zoogeographical provinces of free-living marine animals

Aim We examined the ectoparasite fauna of Sebastes capensis over almost all its geographical distribution range (Chilean, Argentinean and South African coasts) to determine (1) whether the ectoparasites of this host show a zoogeographical pattern and, if so, (2) how this pattern is related to known zoogeographical patterns for free‐living organisms. Location Fish were captured from 20, 24, 30, 33, 36, 40, 45 and 52° S along the Chilean coast; 11° S on the Peruvian coast; 43° S on the Argentina coast; and 34° S on the South African coast. Methods From April to September 2003 and from April to August 2004, 626 fish were captured. The parasites were collected using standard parasitological techniques. At the component community level, zoogeographical distribution patterns were evaluated using cluster analysis. At the infra‐community level, patterns of similarity in parasite composition among localities were investigated with multivariate discriminant analyses. Results The ectoparasite fauna of S. capensis consists of six species distributed along the whole of the Chilean coast. Four other species are distributed only within the transitional zone between the northern warm temperate region (Peruvian faunistic province), extending from Peru to the northern Chilean coast up to c. 30° S, and the cold temperate region (Magellanic faunistic province). The component communities from latitudes 30 to 40° S showed higher ectoparasite species richness, while localities on the margins of the geographical range showed lower species richness. Cluster analysis indicated a grouping of localities consistent with the transitional zone. Argentina and South Africa always emerged as separate localities. Main conclusions The ectoparasite communities of S. capensis do not follow a distributional pattern concordant with the known biogeographical zones for invertebrates and/or fish along the south‐eastern Pacific. Therefore their ectoparasite fauna is not useful as a zoogeographical indicator, although it does allow us to distinguish the transitional zone of the south‐eastern Pacific. On a more extended geographical scale, it is possible to distinguish the ectoparasite communities of S. capensis in the south‐eastern Pacific (as a whole) from those of Argentina and South Africa.     

Diet of the milk shark,Rhizoprionodon acutus (Rüppel, 1837) (Chondrichthyes: Carcharhinidae), from the Senegalese coast

The diet of the milk shark, Rhizoprionodon acutus, from the Senegalese coast (12°30′N–14°45′N) was investigated in 3600 specimens with total lengths ranging from 44 to 113 cm for females and from 45 to 110 cm for males. Conducted from May 2010 to April 2011, the study revealed that of the 3600 stomachs examined, 577 contained food (16.03%). Cumulative prey diversity curves reached a stable level at 175 stomachs and thus the sample size was large enough to describe the overall milk shark diet. Relevant differences in the diet were found between sexes, maturity stages, sampling seasons and locations. The milk shark diet was composed of teleosts, crustaceans, mollucs, nematodes, annelids, and unidentified invertebrates. R. acutus seemed to have a preference for teleosts (98.75% in terms of IRI). The trophic level of milk shark calculated in this study was 4.2.     

Feeding ecology and resource sharing patterns between Stellifer rastrifer (Jordan, 1889) and S. brasiliensis (Schultz, 1945) (Perciformes: Sciaenidae) along the coasts of Paraná and Santa Catarina,Brazil

In this study the diet of Stellifer rastrifer and S. brasiliensis were analysed in order to assess the role of resource partitioning between these congeneric, sympatric and abundant species along the coasts of Paraná (25 °55′28″S; 48 °33′35″W) and Santa Catarina (26 °25′55″S; 48 °34′46″W), in southern Brazil. The stomach contents of 240 S. rastrifer specimens (52–195 mm total length) and 167 S. brasiliensis (60–182 mm total length) collected by trawl boat in March of 2006, were analysed to assess the influence of sites, day and night periods as well as the size class in their diet composition. Although crustaceans have been the main resources of both species, S. rastrifer consumed pelagic and epibenthic items, whereas S. brasiliensis also used benthic resources. Results of permanova analysis provided significant evidence for food resource partitioning and confirm the role of feeding changes in the function of morphology (species, P = 0.001), behaviour (day and night, P = 0.024), and ontogeny (size classes, P = 0.001), strategies to reduce competition and to maintain the coexistence of these syntopic species.     

Phylogeography of the red alga Gracilariopsis tenuifrons (Gracilariales) along the Brazilian coast

Changes in the sea level during the Holocene are regarded as one of the most prevalent drivers of the diversity and distribution of macroalgae in Brazil, influenced by the emergence of the Vitória-Trindade seamount chain (VTC). Gracilariopsis tenuifrons has a wide geographic distribution along the Brazilian coast, from Maranhão state (2°48′64.3" S) to Santa Catarina state (27.5°73′83" S). The knowledge of historical processes affecting diversity may allow the development of conservation strategies in environments against anthropogenic influence. Therefore, knowledge about phylogeography and populational genetic diversity in G. tenuifrons is necessary. Six populations were sampled along the northeastern tropical (Maranhão—MA, Rio Grande do Norte—RN, Alagoas—AL, and Bahia—BA States) and southeastern subtropical (São Paulo “Ubatuba”—SP1 and São Paulo “Itanhaém”—SP2 States) regions along the Brazilian coast. The genetic diversity and structure of G. tenuifrons were inferred using mitochondrial (COI-5P and cox2-3 concatenated) DNA markers. Gracilariopsis tenuifrons populations showed an evident separation between the northeast (from 2°48′64.3" S to 14°18′23" S; 17 haplotypes) and the southeast (from 23°50′14.9" S to 24°20′04.7" S; 10 haplotypes) regions by two mutational steps between them. The main biogeographical barrier to gene flow is located nearby the VTC. The southeast region (São Paulo State) is separated by two subphylogroups (SP1, three haplotypes and SP2, six haplotypes), and Santos Bay (estuary) has been considered a biogeographical barrier between them. The presence of genetic structure and putative barriers to gene flow are in concordance with previous studies reporting biogeographic breaks in the southwest Atlantic Ocean, including the genetic isolation between northeast and southeast regions for red and brown algae in the vicinity of the VTC.     

Geographic variation in photoperiodic diapause induction and diapause intensity in Sericinus montelus (Lepidoptera: Papilionidae)

Abstract Due to the risk of extinction and ornamental value of the swallowtail butterfly, Sericinus montelus Gray (Lepidoptera: Papilionidae) in China, knowledge about local adaptations is important for the conservation and economical utilization of the species. In the present study, photoperiodic diapause induction and diapause intensity of S. montelus populations from Jiamusi (46°37′N), Beijing (40°15′N), Zibo (36°48′N), Fangxian (32°36′N), Wuhan (30°33′N) and Huaihua (27°33′N) were characterized at 25°C. Logistic regression analysis revealed a significant population × hours of light interaction, confirming that photoperiodic responses varied among populations. The critical photoperiod was positively correlated with latitude and increased toward the north at a rate of about 1 h for each 6.67 degrees of latitude. Survival analyses indicated that survival time of diapausing pupae before adult eclosion differed significantly among populations at 25°C and 16 : 8 L : D h. The mean duration of pupal diapause was also positively correlated with latitude. Our study reveals geographic variation in the critical photoperiod for diapause induction and in diapause intensity of S. montelus. These results provide useful information for our general understanding about seasonal adaptation in insects and may also be used to predict how geographic populations respond to climate warming.     

Trophic ecology of the black drum,Pogonias cromis (Sciaenidae), in Mar Chiquita coastal lagoon (Argentina)

This is the first documentation on the feeding habits of the black drum, Pogonias cromis, in waters of South America. The aim of the investigation was to determine the trophic ecology of P. cromis in the Mar Chiquita coastal lagoon (37°32′–37°45′S; 57°19′–57°26′W) from stomach content analyses of 109 P. cromis specimens. Samples in various sizes were collected monthly using various types of fishing gear. The results showed that this species is a benthic predator focusing on bivalves and crabs. permanova results indicated significant seasonal differences in the diet. This pattern reflected seasonal changes in prey abundance and availability, which produced changes in both foraging strategy and trophic niche breadth. This indicates that P. cromis is a versatile predator, adapting its feeding strategy in response to a seasonal shift of prey abundance, and indicating an opportunist behavior.     

Ontogenetic diet shifts of rough scad Trachurus lathami in the North Patagonian shelf (south-west Atlantic Ocean)

Rough scad Trachurus lathami is a key pelagic fish in the Argentinean continental shelf (ACS, south-west Atlantic Ocean), with recent increases in abundance. It is a main prey of fishes and marine mammals, and shares the environment with commercially relevant pelagic species (Engraulis anchoita and Scomber colias), playing an important role linking lower and upper trophic levels in the ecosystem. This study aims to determine the ontogenetic changes in the diet composition, feeding strategy, trophic niche breadth and trophic level of T. lathami in the North Patagonian Shelf (43°–45°30′S). The stomach contents of adult fish (n = 238) were analysed. The results suggest a clear ontogenetic shift in the diet at a size of ~190 mm. Smaller individuals (160–190 mm) were specialized on misidaceans, and showed the highest trophic level, while larger T. lathami (221–230 mm) consumed decapods (Peisos petrunkevitchi) and teleosts (eggs and larvae). Trophic niche breadth was higher at the medium-sized class (191–220 mm), which mainly preyed on copepods (Calanoides carinatus) and chaetognaths (Sagitta spp.), evidencing a more diverse diet and a rather generalist strategy. Updated information on the trophic ecology of T. lathami evidences its extremely plastic feeding behaviour, being able to adapt its trophic niche to the most readily available food items from the mesopelagic community.     

First record of <Emphasis Type="Italic">Cymatium keenae</Emphasis> Beu, 1970 (Mollusca: Ranellidae) from Antofagasta Bay,northern Chile,in connection with El Niño events

Cymatium (Monoplex) keenae Beu, 1970, the neopolitan triton, is a Ranellidae predator distributed in tropical and subtropical waters. In this study we report this species for the first time in Antofagasta Bay, northern Chile. Adult specimens have been found since June 2003 at depths ranging from 5 to 15 m in La Rinconada Marine Reserve (23°28′18″S, 70°30′46″W) in Antofagasta Bay, near a scallop farming facility. The present findings clearly extend the geographic range of C. keenae, which previously had been reported from La Paz, Gulf of California (Mexico) to Galápagos Islands (Ecuador) in the SE Pacific. Previous evidence strongly suggests that the intrusion of this tropical immigrant can be related to warm El Niño episodes. We analyze the key role of the oceanographic characteristics of Antofagasta Bay as potential temporal refuge for this species.     

The zoogeography of algae-associated peracarids along the Pacific coast of Chile

Abstract Aim To describe the zoogeography of the algae‐associated peracarid crustaceans from exposed rocky shores along the SE‐Pacific. Location Chile, 18° S to 42° S. Methods A standardized sampling programme was used at all sites. Samples of macroalgae were taken at twenty sites distributed along the entire study area. Quantitative samples (n = 6 replicates of 8 cm^?2 surface area each) of calcareous and non‐calcareous red algae were taken in the low intertidal, preserved immediately in 4%‐formalin and washed over a 0.2‐mm mesh before sorting. All peracarid individuals were sorted, identified to the species level and then categorized in separate functional groups according to their feeding habits. Graphical representations of species replacement within each functional group along the latitudinal gradient are provided. A classification analysis employing the unweighted paired group method using arithmetic average (UPGMA) was conducted in order to reveal the main zoogeographical zones. Results A total of forty epifaunal peracarid species was found. A gradual replacement of species within different functional groups (grazing and suspension‐feeding species) was observed in the central region (c. 26° S?37° S). In this central region, species with northern and those with southern distribution overlapped, while other species were only found here, resulting in high species richness. The number of species/site/algal species in the northern (north of c. 25.5° S) and southern region (south of c. 38.5° S) was considerably lower than in the central region. The distribution of most grazing peracarids showed a more continuous pattern than that of suspension‐feeding amphipods. The distribution of the remaining species (predators, scavengers, deposit‐feeders, unknowns) was scattered along the examined sites. The cluster analysis for the epifaunal peracarid assemblage confirmed the separation of a northern and southern zone connected by a central (transitional) zone between c. 26° S and c. 37° S. Similar zonation patterns have been found by most other studies on the zoogeography of the Chilean coast, although little agreement exists about the exact limits of this transitional zone. It is discussed that the distribution limits of algae‐associated peracarids (and other macroinvertebrates) – particularly in the transitional zone – may show interannual variations as a result of varying oceanographic conditions. The large affinity of the algae‐associated peracarid fauna from the central and southern Chilean coast to those of other regions indicates that dispersal may be facilitated by rafting with floating algae transported in the Antarctic Circumpolar Current. Main conclusions The zoogeographical analysis of algae‐associated peracarids confirms the existence of a northern and a southern zone connected by an extensive transitional zone. General biology, habitat use and the abundant presence of dispersal vectors such as floating macroalgae may affect the zoogeography of species living in transitional zones with strong interannual variations in current regimes. In these areas, species associated with substrata of high dispersal potential may show different distribution patterns than species inhabiting other substrata.     

Biogeographical patterns in endoparasite communities of a marine fish (Sebastes capensis Gmelin) with extended range in the Southern Hemisphere

Aim The endoparasites of Sebastes capensis Gmelin are examined over most of its geographical range (coasts of Peru, Chile, Argentina and South Africa) to determine: (1) whether the endoparasite communities of this fish show zoogeographical patterns; and (2) if so, whether there are any relationships between spatial variations in the endoparasite fauna and known zoogeographical patterns for marine free‐living organisms (e.g. prey that are included in the life cycles of endoparasites). Location Fish were captured at nine localities along the Pacific coast of South America, from 11° S in the centre of the Peruvian coast, to 52° S in southern Chile, and also at two localities in the Atlantic Ocean, at 43° S in Argentina, and 34° S in South Africa. Methods From April to September 2003 and April to August 2004, 626 fish were captured. Endoparasites and diet were examined following traditional methods. Cluster analyses were used to evaluate the distribution patterns of the endoparasite communities, and to evaluate similarities in the prey composition per locality. Results The endoparasite fauna of S. capensis consisted of four species widely distributed along the Pacific coast: Ascarophis cf. sebastodis, Anisakis sp., Corynosoma australe, and Pseudopecoelus sp. Other parasites were distributed only in some geographical areas. The species richness of the parasite communities increased with latitude along the Pacific coast, while parasite communities from Argentina and South Africa showed low species richness. Cluster analyses based on endoparasite composition and on prey composition grouped localities in a way consistent with known biogeographical areas for marine free‐living organisms. Main conclusions The endoparasites of S. capensis exhibit a pattern associated with known biogeographical areas for free‐living organisms. The latitudinal increase in endoparasite community richness is associated with changes in prey composition (intermediate hosts) and also possibly with the presence of definitive hosts. Therefore, the biogeographical patterns of prey are considered key determinants of the endoparasite community structure of the host.