Impact of harvesting cleaner fish for salmonid aquaculture assessed from replicated coastal marine protected areas

Wrasse (Labridae) fisheries have increased markedly in Norway since 2010. Wrasse are being used as cleaner fish in salmonid aquaculture to control sea-lice infestations. However, fundamental knowledge on the demography and abundance of the targeted wrasse populations in Norwegian waters is lacking, and the consequences of harvesting at the current intensity have not been assessed. Here, we compared catch per unit effort (CPUE), size, age and sex ratio of goldsinny wrasse (Ctenolabrus rupestris) and corkwing wrasse (Symphodus melops) between marine protected areas (MPAs) and control areas open for fishing at four localities on the Skagerrak coast in Southern Norway. The CPUE of goldsinny larger than the minimum size limit was 33–65% higher within MPAs, while for corkwing three of four MPAs had higher CPUE with the relative difference between MPAs and control areas ranging from ?16% to 92%. Moreover, corkwing, but not goldsinny, was significantly older and larger within MPAs than in control areas. Sex ratios did not differ between MPAs and control areas for either species. Our study suggests that despite its short history, the wrasse fisheries have considerable impacts on the target populations and, further, that small MPAs hold promise as a management tool for maintaining natural population sizes and size structure. Goldsinny, being a smaller-sized species, also seems to benefit from the traditional minimum size limit management tool, which applies outside MPAs.     

Niche overlap and diet composition of three sympatric coastal dolphin species in the southwest Atlantic Ocean

Sympatric species are expected to differ in ecological requirements to minimize niche overlap and avoid competition. Here we assess the trophic interactions among three coexisting dolphin species from southern Brazil: the franciscana dolphin (Pontoporia blainvillei), the Guiana dolphin (Sotalia guianensis), and the Lahille's bottlenose dolphin (Tursiops truncatus gephyreus). We evaluated temporal variation in carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values of bone collagen to examine potential dietary shifts resulting from increased fishing activity over the past three decades. We estimated the degree of niche overlap among these species and the contribution of potential prey sources to their diet. δ¹⁵N values were consistent among species and across years, while δ¹³C values increased for Guiana dolphins and decreased for bottlenose dolphins, suggesting changes in diet and/or foraging habitats through time. The similar δ¹³C and δ¹⁵N values and the high niche overlap between Guiana and bottlenose dolphins indicate that these species are primarily feeding on demersal prey. The franciscana diet is primarily composed of pelagic prey, resulting in a lower niche overlap in comparison with the other dolphin species. Our study provides further information about the foraging ecology of this unique dolphin community in southern Brazil with implications for its management and conservation.     

Mazocraeid monogeneans parasitic on Engraulid fishes in the southwest Atlantic

Two species of mazocraeid monogeneans are reported for the first time from Argentinean-Uruguayan engraulid fish hosts, Engraulis anchoita and Anchoa marini. Mazocraes australis n. sp. collected from the gills of E. anchoita is described: this new species can be distinguished from the other congenerics by the number of genital hooks in the copulatory organ, the relative size of clamps, and the number of hooks in the terminal lappet. Pseudanthocotyloides heterocotyle found in the gills of E. anchoita and A. marini is redescribed. The diagnosis of both mazocraeid genera are also emended.     

Diversity of settlement-stage reef fishes captured by light-trap in a tropical south-west Atlantic Ocean coastal reef system

This study reports the results of 5 years of monitoring reef fish post-larvae using light traps in the Bay of Tamandaré, north-east Brazil. An annotated checklist of pre-settlement fish species, their frequency of occurrence and taxonomic characteristics are provided. In total, 4,422 post-larval fishes belonging to 36 families, 56 genera and 76 species were captured. The most species-rich families were Carangidae (7), Lutjanidae (6) and Pomacentridae (4), while the families Gerreidae (30.47%), Holocentridae (16.54%), Blenniidae (12.01%), Labrisomidae (8.36%), Lutjanidae (8.29%) and Acanthuridae (5.95%) were the most abundant. This is the first study of the taxonomic diversity and assemblage structure of settlement-stage reef fishes in the tropical south-west Atlantic Ocean. Although a few common species were not captured due to selectivity of light traps, the composition and taxonomic diversity of this first collection suggests that light traps are useful for studies of the early life history of a wide range of pre-settlement reef fishes.     

Environmental and spatial effects on coastal stream fishes in the Atlantic rain forest

Contemporary and historical factors influence assemblage structure. The environmental and spatial influences acting on fish organization of rain forest coastal streams in the Atlantic rain forest of Brazil were examined. Fish (and functional traits such as morphology, diet, velocity preference, body size), environmental variables (pH, water conductivity, dissolved oxygen, temperature, stream width, flow, depth, substrate), and altitude were measured from 59 stream reaches. Asymmetric eigenvector maps were used to model the spatial structure considering direction of fish movements. Elevation played an important role—fish abundance, biomass, and richness all decrease with increasing elevation. Fish communities are influenced by both environmental and spatial factors, but downstream movements were shown to be more important in explaining the observed spatial variation than were bidirectional and upstream movements. Spatial factors, as well as environmental variables influenced by the spatial structure, explained most of the variation in fish assemblages. The strong spatial structuring is probably attributable to asymmetric dispersal limitation along the altitudinal profile: Dispersal is likely to be more limiting moving upstream than downstream. These fish assemblages reflect scale-dependent processes: At the stream-reach scale, fish respond to local environmental filters (habitat structure, water chemistry, and food supply), which are in turn influenced by a larger scale, namely the altitudinal gradient expected in steep coastal mountains. Thus, environmental drivers are not independent of spatial factors, and the effects of local factors can be confounded across the altitudinal gradient. These results may have implications for conservation, because downstream reaches are often neglected in management and conservation plans.     

Antifreeze glycoprotein levels in Antarctic notothenioid fishes inhabiting different thermal environments and the effect of warm acclimation

A quantification method was developed to determine the concentrations of the major antifreeze glycoprotein (AFGP) isoforms in the blood of Antarctic notothenioid fishes. Serum samples were precipitated with 2.5% TCA and the supernatant containing AFGPs were chromatographed on an HPLC size exclusion column and the concentrations of the major AFGP size classes were determined from the areas of the corresponding peaks in the elution profile. Eight species of Antarctic notothenioid fishes were examined and their blood AFGP concentrations varied from 5 to 35 mg/mL. All of these fishes synthesized both the large and small AFGPs, but maintained higher levels of small AFGPs than the large ones in their blood. The species inhabiting more severe water environments (lower temperature and presence of ice) had higher serum AFGP levels than those in milder environments. The cryopelagic Pagothenia borchgrevinki decreased their blood AFGP concentrations in response to warm acclimation, but to a much lower extent in comparison to the antifreeze-bearing fishes in the Northern Hemisphere. After being warm acclimated at +4 degrees C for 16 weeks, the serum concentrations of the small and large AFGPs were decreased by about 60% and 20%, respectively.     

New records of warm‐temperate water fishes in central Patagonian coastal waters (Southwestern South Atlantic Ocean)

In the Province of Chubut (43°S–47°S), from 2001 to 2005 an on‐board observers program analyzed 18 903 fishing hauls captured at depths of 19–104 m. Sport fishing tournaments near Puerto Rawson, Chubut, were also monitored from 2004 to 2006. The aim was to document the southward expansion of five cartilaginous fish species and ten bony fish species caught in Central Patagonian waters (Argentina): Psammobatis extenta, Psammobatis bergi, Atlantoraja castelnaui, Sympterygia acuta, Torpedo puelcha, Selene setapinnis, Oncopterus darwini, Dules auriga, Mullus argentinae, Cynoscion guatucupa, Prionotus nudigula, Conger orbignyanus, Urophycis brasiliensis, Trachurus lathami, and Trichiurus lepturus. Reproductive populations of S. acuta, O. darwini and C. guatucupa were detected in the Engaño Bay area close to Puerto Rawson (43°10′S–43°19′S). The newly reported fishes pertain to warm‐temperate waters, where most of the species are native to the Argentinean Zoogeographic Province. One likely hypothesis explaining their occurrence in the area is the prevalence of higher water temperatures in recent times in the San Jorge Gulf and adjacent waters. Another likely hypothesis is the increase in sampling and catch efforts in Patagonian coastal areas and also improved capabilities in taxonomic recognition of the species.     

Physiological characteristics of wild Atlantic salmon post-smolts during estuarine and coastal migration

Changes were measured in some of the major physiological variables associated with seawater adaptability, growth and energetics in wild Atlantic salmon Salmo salar smolts and post-smolts migrating from the river and through the estuary, fjord and coastal areas in the River Orkla and the Trondheimsfjord, Norway during late May to early June. Gill Na⁺,K⁺-ATPase activity increased to levels of 12–16 µmol ADP mg protein⁻¹ h⁻¹ in post-smolts caught in higher salinity zones, probably representing long-term levels of Atlantic salmon post-smolts in oceanic conditions. Muscle moisture was regulated within narrow limits (77·7–78·7%) in fish from all zones during both years, suggesting that post-smolts adapt to marine conditions without any long-term disturbance of hydro-mineral balance. Lipid and glycogen content showed a general trend towards depletion from the river, through the fjord and into the ocean. There was, however, no significant change in protein content. The present results confirm that smolts are naturally 'energy deficient' during downstream migration, and suggest that post-smolts also mobilize energy reserves during their early marine phase, while protein is allocated for somatic growth. Plasma growth hormone (GH) levels increased transiently during passage through the estuary and fjord, with lower levels observed in post-smolts caught off-shore, i.e. in fish which were feeding on marine prey and had adapted to the marine environment. These physiological changes may confer substantial selective advantages during the critical early marine phase of anadromous salmonids, and hence are adaptive for long-term survival in sea water.     

Fellodistomidae and Zoogonidae (Digenea) of deep-sea fishes of the NW Atlantic Ocean

The following species are described from fishes in deep-waters of the northwestern Atlantic Ocean: Fellodistomidae: Steringophorus furciger from Antimora rostrata, Coryphaenoides (Lionurus) carapinus, Lycenchelys paxillus, L. verrillii and Lycodes atlanticus; S. blackeri from Xenodermichthys copei, S. haedrichi n. sp. from Porogadus milesi, characterised by its lobate testes, sucker-ratio and long vitelline fields Megenteron crassum from Dicrolene intronigra; Zoogonidae: Brachyenteron rissoanum n. sp. from Polyacanthonotus rissoanus, characterised by the ovary position, the saccular seminal vesicle, the marginal genital pore and egg-size; Koiea notacanthi n. g., n. sp. from Notacanthus (?) chemnitzi, characterised by the Y-shaped excretory vesicle and the posteriorly placed testes.     

Comparative metabolic rates of common western North Atlantic Ocean sciaenid fishes

The resting metabolic rates (R(R)) of western North Atlantic Ocean sciaenids, such as Atlantic croaker Micropogonias undulatus, spot Leiostomus xanthurus and kingfishes Menticirrhus spp., as well as the active metabolic rates (R(A)) of M. undulatus and L. xanthurus were investigated to facilitate inter and intraspecific comparisons of their energetic ecology. The R(R) of M. undulatus and L. xanthurus were typical for fishes with similar lifestyles. The R(R) of Menticirrhus spp. were elevated relative to those of M. undulatus and L. xanthurus, but below those of high-energy-demand species such as tunas Thunnus spp. and dolphinfish Coryphaena hippurus. Repeated-measures non-linear mixed-effects models were applied to account for within-individual autocorrelation and corrected for non-constant variance typical of noisy R(A) data sets. Repeated-measures models incorporating autoregressive first-order [AR(1)] and autoregressive moving average (ARMA) covariances provided significantly superior fits, more precise parameter estimates (i.e. reduced s.e.) and y-intercept estimates that more closely approximated measured R(R) for M. undulatus and L. xanthurus than standard least-squares regression procedures.     

西南大西洋阿根廷滑柔鱼生物学年间比较

将2007年2—5月、2008年3—5月、2010年1—3月我国鱿钓船在西南大西洋公海海域采集的阿根廷滑柔鱼样本,比较其不同年间的生物学特性。结果表明,渔获物雌雄比为1.14—1.50:1;3a雌性个体的胴长(体重)分别为188—346mm(110—856g)、200—364mm(145—950g)、124—276mm(72—425g),雄性个体的胴长(体重)为178—298mm(102—703g)、193—314mm(145—680g)、104—335mm(70—374g)。2010年渔获个体明显比2007和2008年小。各年间及雌、雄个体间的体重与胴长关系均存在差异(P<0.001),渔获物中年间性成熟组成差异明显,此外各年3月份渔获个体也存在显著差异。雌、雄个体的胴长平均生长率分别为0.53—1.07 mm/d、0.47—0.68 mm/d,相对生长率分别为0.24—0.41%d-1、0.23—0.33%d-1;雌、雄个体的体重平均生长率在1.70—5.25 g/d、1.64—4.59 g/d,相对生长率分别为0.92—1.37%d-1、0.86—1.40%d-1。渔汛期间,胴长、体重与时间的关系均符合指数生长曲线,但生长指数年间差异明显。综合分析认为:2007年渔获物基本上为南巴塔哥尼亚种群;2008年以南巴塔哥尼亚种群为主,但也有少量较小个体的夏季产卵种群;2010年则以夏季产卵种群为主,并有少量的南巴塔哥尼亚种群。     

New records of coastal fishes in the northern Rio de Janeiro State, Brazil, with comments on the biogeography of the south-western Atlantic Ocean

The distribution limits in the Atlantic of Callorhinchus callorynchus (Callorhinchidae) and Odontesthes argentinensis (Atherinopsidae) are extended northwards to 22° 22' S and 22° 31' S, respectively, whereas that of Lile piquitinga (Clupeidae) is extended southwards to 22° 22' S. Their occurrence in the north of Rio de Janeiro State is discussed. Remarks on the osteology of O. argentinensis, and morphometric and meristic data of L. piquitinga, are also provided.     

Social organization and reproductive behavior of ostraciid fishes from Japan and the Western Atlantic Ocean

Social organization and reproductive behavior were studied in 4 species of ostraciid fishes.Lactoria fornasini andLactoria diaphana from Japan andAcanthostracion polygonius from the western Atlsnyiv were usually found in single male, haremic social groups, although the latter 2 species usually included only 2 females per harem, and individuals in all 3 species foraged solitarily. Elements of both “resource defense” and “female defense” (Emlen & Oring 1977) were evident in the 2Lactoria species, and female defense appeared particularly intense inL. diaphana. Resource defense was apparent inA. polygonius. Lactophrys triquetor occurred in lek-like breeding assemblages at Curacao (Netherlands Antilles) and on the Atlantic coast of Panama. These variations in social organization are discussed and a relationship with feeding habits is suggested. All 4 species appear to be gonochores (demonstrated inLactoria by Moyer 1979). The 2Lactoria spp. showed operational sex ratios (OSR: Emlen & Oring 1977) approaching 1∶1 and a high degree of female spawning synchrony. The occurrence of polygyny in species with 1∶1 OSRs and female spawning synchrony is discussed with reference to the Knowlton (1979) model which predicts monogamy to occur in such situations.     

Blooms of single bacterial species in a coastal lagoon of the southwestern Atlantic Ocean

We investigated seasonal differences in community structure and activity (leucine incorporation) of the planktonic bacterial assemblage in the freshwater and brackish-water zones of a shallow coastal lagoon of the southwestern Atlantic Ocean. Alphaproteobacteria formed the dominant microbial group in both zones throughout the sampling period. After an intrusion of marine water, members of the SAR11 lineage became abundant in the brackish-water zone. These bacteria were apparently distributed over the lagoon during the following months until they constituted almost 30% of all prokaryotic cells at both sampling sites. At the first sampling date (March 2003) a single alphaproteobacterial species unrelated to SAR11, Sphingomonas echinoides, dominated the microbial assemblages in both zones of the lagoon concomitantly with a bloom of filamentous cyanobacteria. Pronounced maxima of leucine incorporation were observed once in each zone of the lagoon. In the freshwater zone, this highly active microbial assemblage was a mix of the typical bacteria lineages expected in aquatic systems. By contrast, a single bacterial genotype with >99% similarity to the facultative pathogen gammaproteobacterial species Stenotrophomonas maltophilia formed >90% of the bacterial assemblage (>10(7) cell ml(-1)) in the brackish-water zone at the time point of highest bacterial leucine incorporation. Moreover, these bacteria were equally dominant, albeit less active, in the freshwater zone. Thus, the pelagic zone of the studied lagoon harbored repeated short-term blooms of single bacterial species. This finding may have consequences for environmental protection.     

Genetic identification of Carcharhinus sharks from the southwest Atlantic Ocean (Chondrichthyes: Carcharhiniformes)

Sharks of the genus Carcharhinus exhibit subtle morphological differences that are difficult to observe because of the common practice of head and fin removal, making species identification challenging. A total of 317 sharks, commonly called ‘cação‐baia’ (large individuals) or ‘machote’ (small size) in Brazil, were captured by the tuna fleet at the Santos and Guarujá fishery ports on the southeastern coast of Brazil and identified at the species level by multiplex PCR. The Internal Transcribed Spacer 2 region of ribosomal DNA was amplified using universal primers, and species‐specific primers were used for some of the Carcharhinus species. A total of 313 shark carcasses were directly identified by multiplex PCR. Four carcass samples did not amplify; therefore, the partial COI sequences were used to confirm their taxonomic identity. The results show that more than one species was being traded under the same commercial designation, including some Carcharhinus species that are under protection by federal legislation. Such species misidentification directly affects the long‐term sustainability of sharks.     

Quantitative and qualitative studies of gut flora in striped bass from estuarine and coastal marine environments

Examination of the intestinal contents of 130 striped bass (Morone saxatilis) collected from the Hudson River and Long Island Sound during May to October 1981 showed that opportunistic fish pathogens--especially Aeromonas hydrophila--predominated in samples from both locations. Other isolates from both groups of striped bass included Vibrio, pseudomonads, flavo-bacteria, Alcaligenes, and enterics. Small numbers of Micrococcus, Bacillus, Corynebacterium, and Acinetobacter were also isolated. Total numbers of bacteria in the intestines were 100 to 1,000 times higher in striped bass from the Hudson River than in those from Long Island Sound.     

A new species of monorchiid digenean from marine fishes in the Southwestern Atlantic Ocean off Patagonia

Proctotrema bartolii n. sp. (Digenea: Monorchiidae) is described based on naturally and experimental obtained adults from the marine fishes Odontesthes smitti (Lahille), O. nigricans (Richardson) (Atherinopsidae) and Eleginops maclovinus (Cuvier) (Eleginopidae) off Patagonia, Argentina, in the Southwestern Atlantic Ocean. Its generic identification is based on the presence of a unipartite terminal organ with the metraterm uniting with its distal region, an unarmed genital atrium, a single testis, a vitellarium follicular lateral to the ovary and ventral sucker, and uterine coils occupying most of hindbody. The new species differs from P. bacilliovatum Odhner, 1911, P. amphitruncatum Fischthal & Thomas, 1969 and P. guptai Ahmad & Dhar, 1987 in having a smaller body (305–650 vs 1,600–3,080, 1,500–1,800 and 2,150–2,670 μm, respectively), a round vs funnel-shaped oral sucker, a smooth vs lobed ovary, a saccular rather than tubular excretory vesicle, the number of vitelline follicles (12–16 vs 8–9, 9 and 6–8, respectively), and wider eggs (25–31 × 15–20 vs 28–37 × 9–12, 24–28 × 7–10, and 24–30 × 8–10 μm, respectively). Moreover, the new species differs from P. bacilliovatum and P. amphitruncatum in having a saccular rather than a coiled seminal vesicle, and from P. bacilliovatum and P. guptai in having its tegument completely vs partly spined. Proctotrema Odhner, 1911 is considered to be restricted to these four species. This is the first report of a species of this genus from South American waters.     

New plagioporines (Digenea: Opecoelidae) from deep-sea fishes of the North Atlantic Ocean

Three new species of digenean are described from demersal fishes taken in deep waters of the northwestern and northeastern Atlantic Ocean: Podocotyle schistotesticulata n. sp. from Antimora rostrata; P. harrisae n. sp. from Coryphaenoides (Lionurus) carapinus; and Gaevskajatrema halosauropsi n. sp. from Halosauropsis macrochir. The status of the nominal species of the genus Podocotyle Dujardin, 1845 is presented in annotated summary, along with a tabulation of the distinctive characteristics of recognised species of the genus. Gaevskajatrema Gibson & Bray, 1982 is discussed and its diagnosis amended.