Pelagic Resources Research Articles

Evidence for enhanced late-stage larval quality, not survival, through maternal carry-over effects in a space monopolizing barnacle

Understanding the effects of maternal and pelagic resource allocation on larval traits is essential to better understand population dynamics of marine benthic invertebrates. We tested how different levels of food supply to adult barnacles and their feeding larvae (nauplii) might alter survival to the settling cyprid larval stage and cyprid quality. Median development time did not vary, except when both parents and larvae were given a low food supply, which delayed the time to metamorphosis by over 40%. Survival to the cyprid stage was only affected by larval feeding, which doubled in better-fed nauplii. In contrast, cyprid size showed a more complex response, prone to additive effects of maternal and larval provisioning. Moreover, the resulting size-range observed for experimental cyprids (spanning over 70% of the minimum cyprid size) mirrored the variation found in the coastal plankton, suggesting that food supply may exert similar effects in nature. Given that barnacles nearly saturate available habitat under favorable conditions, maternal allocation resulting in enhanced late-stage larval quality may be adaptive since competition for available settling space is likely intense. On the other side, severe resource limitation through embryogenesis and larval development may impose delayed metamorphosis and thus enhanced potential for transport and the colonization of marginal habitats, where intraspecific competition may be lower and larval quality less critical.

Stable isotopes reveal different dependencies on benthic and pelagic pathways between Munida gregaria ecotypes

Forage species are key nodes in the energy fluxes between benthic and pelagic zones. The squat lobster, Munida gregaria, is a common forage species of the Southern Hemisphere and its abundance is increasing. This species presents two ecotypes: one (subrugosa) that settles on the sea bottom immediately after the metamorphosis and another (gregaria) that remains in the water column for a variable period of time, before adopting a benthic habit. Hypotheses on its settlement are conflicting; one proposes that it is a density-dependent process of the sea bottom and the other that it is regulated by the availability of pelagic food. To rule out whether feeding factors could be significant in the decision-making process, the first step is to identify whether the ecotypes have different diets or not. This study compared the isotopic niche location, the trophic levels and the reliance on benthic or pelagic resources between ecotypes. Among all sampling events, the isotopic niches of the gregaria and the subrugosa ecotypes were significantly distant from each other. In addition, the difference in δ13C values between ecotypes covered an average of 75% of the total difference between pelagic and benthic pathways. Benthic individuals relied mostly on benthic animals, while pelagic individuals relied on pelagic primary producers. Overall, results show that each ecotype feeds mainly on different energy pathways. Considering its feeding ecology and movements during life history, M. gregaria is a key component of bentho-pelagic coupling.

Characteristics of consumer trophic resources for Waikato shallow lake food webs

ABSTRACTWe characterised the quantity (mass per unit area or volume), quality (cabon:nitrogen ratio) and enrichment (δ15N) of basal food resources and benthic macroinvertebrates in six shallow lakes in the Waikato region, New Zealand, to elucidate patterns related to lake type (peat, riverine), habitat (littoral, mid-lake) and enrichment status (Trophic Level Index >6 or ≤5). Total seston dry mass was dominated by fine material that was correlated with chlorophyll a concentration. Seston was a higher quality food resource than benthic particulate organic matter which had higher biomass overall in littoral than in mid-lake habitats. Biomass of Chironomidae was highest in the less-enriched peat lakes, possibly due to clearer water supporting benthic algae in shallow littoral areas. Our results highlight the potential role of multiple bottom-up influences on shallow lake food webs. The more abundant and higher quality pelagic food resources in highly enriched lakes may have implications for resilience to non-indigenous fish invasion.

Spatial and Temporal Fishing Patterns at the Outer Banks of the Southern California Bight

We analyzed recreational and commercial catch records from 1980 to 2009 for the fishing blocks associated with the 5 southern offshore banks of the Southern California Bight (Cortes Bank, Tanner Bank, Northeast Bank, Cherry Ridge, and Garrett Ridge). Recreational fishers and divers targeted pelagic taxa (e.g., tunas and Yellowtail) but instead landed more benthic taxa (e.g., rockfishes, Ocean Whitefish, and California Sheephead). For the commercial fisheries, pelagics (Bluefin Tuna, Albacore, Skipjack, Yellowfin Tuna, Pacific Bonito, and Swordfish) were the most important taxa and represented a significant proportion (8%–27%) of the landings of these fishes in the bight. These fishes were caught primarily at Cortes and Tanner Banks, which together only represent 3.7% of the fishing grounds in the region. In addition, this proportion of catch of these critical species has been significantly increasing at the outer banks during this period. Based on their geography and physical oceanography, we propose that these offshore banks comprise a unique habitat for pelagic resources in the Southern California Bight.

Utilization and Management Model of Pelagic Fish Resources

Pelagic fish was the main raw material for fish processing industry. Rate of fishing that not equivalent with the growth of fish resources, eventually will decrease the catch of fishermen. Aims of the research were (1) to estimate the bioeconomic of pelagic fish resources on MSY (Maximum Sustainable Yield), MEY (Maximum Economic Yield) and OA (open Access) conditions; (2) to estimate the optimum utilization rate, (3) arrange the management model of sustainability pelagic fish resources in Pati regency. This research was descriptive quantitative and conducted in March until September 2017. Reseacrh location in Bajomulyo village and Bendar village Juwana Subdistrict with 35 samples. Data analysis : (1) gear standardization, (2) bioeconomic static optimation model approach, (3) bioeconomic dinamic optimation model approach, (4) reconstruction of in-depth interview results. Result of the research are (1) bioeconomic static optimation model approach namely, biomass MEY>MSY>OA, catch MSY>MEY>OA, effort OA>MSY>MEY, profit MEY>MSY>OA; (2) bioeconomic dinamic optimation model approach namely, biomass MEY>MSY>OSY>OA, catch MSY>MEY>OSY>OA, effort OA>MSY>OSY>MEY, profit MEY>>OSY>MSY>OA; (3) pelagic fish management model are input controlling, output controlling and technical provisions.

Feeding ecology of a common benthic fish, shorthorn sculpin (Myoxocephalus scorpius) in the high arctic

Shorthorn sculpin (Myoxocephalus scorpius) commonly occur in nearshore areas during open water periods in the Arctic, yet little is known about their feeding strategies or trophic roles. This study used carbon (δ13C) and nitrogen (δ15N) stable isotopes (SIs) and stomach content analysis (SCA) to assess shorthorn sculpin trophic position (TP), carbon sources, dietary specialization and prey selection, and the significance of polar cod (Boreogadus saida) in their diet across body size and multiple years. Sculpin TP increased with body size [range = 4.0 ± 0.1 ( 25 cm)] and was consistent with SCA; smaller individuals fed predominantly on invertebrates while larger fed more on fishes. Shorthorn sculpin had high % reliance on pelagic resources (α) for a benthic fish, from 0.62 ± 0.05 to 0.63 ± 0.06, thus coupling benthic and pelagic sources. Dietary specialization based on SIs in liver and muscle occurred in all size groups, and along with TP and niche width varied between years, generally increasing with fish found in SCA. The presence of polar cod, absent two of the four study years, did not significantly affect any dietary metrics measured in shorthorn sculpin, and cannibalism appears to have had a greater impact on shorthorn sculpin trophic ecology. This study demonstrates that shorthorn sculpin are an important secondary to tertiary consumer in nearshore Arctic marine habitats due to coupling multiple trophic pathways, demonstrating plasticity in diet between years, and exploiting an array of prey across size ranges.

Food depletion regulates the demography of invasive dreissenid mussels in a stratified lake

AbstractLake stratification produces sharp gradients in temperature and pelagic resources which have cascading effects on the traits of aquatic populations, including invasive species and their ecosystem impacts. We study the consequences of such common environmental gradients on the demography of quagga mussels, one of the world's most aggressive invasive species. Coupling a series of in situ experiments with a biophysical model of the pelagic community, we quantify mussel growth and recruitment in littoral vs. profundal benthic habitats of eastern Lake Erie. We found that both severe food depletion and cold temperatures in the hypolimnion during summer stratification cause mussels to grow twice as slowly and currently inhibit recruitment in profundal compared to littoral habitats. Together with the high biomass and large mean mussel size found in long‐term monitoring surveys in the profundal habitats, our results imply that mussels successfully colonizing profundal habitats have relatively long lifespans with low growth rates, and therefore lower productivity, compared to mussels in shallow areas. Consequently, the bulk of dreissenid biomass in Lake Erie and other Great Lakes found in the vast but resource‐poor profundal habitats may have very limited impacts on epilimnetic communities compared to mussels in littoral areas. By contrast, mussels in profundal habitats strongly reduce food availability to hypolimnetic communities throughout the year. Thus, our results explain how the ecosystem impacts of sessile freshwater invaders are likely to vary among habitats and lakes depending on the relative size of profundal populations and the extent of stratification.

Mobile marine predators: an understudied source of nutrients to coral reefs in an unfished atoll.

Animal movements can facilitate important ecological processes, and wide-ranging marine predators, such as sharks, potentially contribute significantly towards nutrient transfer between habitats. We applied network theory to 4 years of acoustic telemetry data for grey reef sharks (Carcharhinus amblyrhynchos) at Palmyra, an unfished atoll, to assess their potential role in nutrient dynamics throughout this remote ecosystem. We evaluated the dynamics of habitat connectivity and used network metrics to quantify shark-mediated nutrient distribution. Predator movements were consistent within year, but differed between years and by sex. Females used higher numbers of routes throughout the system, distributing nutrients over a larger proportion of the atoll. Extrapolations of tagged sharks to the population level suggest that prey consumption and subsequent egestion leads to the heterogeneous deposition of 94.5 kg d-1 of nitrogen around the atoll, with approximately 86% of this probably derived from pelagic resources. These results suggest that sharks may contribute substantially to nutrient transfer from offshore waters to near-shore reefs, subsidies that are important for coral reef health.

What is the invasiveness of Hemimysis anomala (Crustacea, Mysidae) in the large deep Lake Bourget, France?

Non-native species are a major threat to aquatic ecosystems and the assessment of their invasiveness may be limited by the diverse ecological features needed to be accounted for. In this study, we combined complementary features of the autoecology and trophic ecology of Hemimysis anomala in a large deep lake (Lake Bourget) to assess its invasiveness. It was present in more than 80% of the 23 sites explored, indicating an extensive colonization of the lake. The mysid exhibited at least two generations per year, and the median individual growth rate was ~ 0.04 mg dry mass day−1 and ~ 0.09 mg dry mass day−1 for juveniles and adults, respectively. Consequently, the daily production for a typical reproductive swarm could reach more than 250 mg dry mass day−1 m−2 representing an important hotspot of secondary production. Individual measurements of stable carbon (δ13C) and nitrogen (δ15N) isotopes highlighted a trophic ontogenetic shift and indicated that subpopulations of H. anomala could mainly rely either on benthic or pelagic resources depending on the slope of the site. Because of its extensive colonization, its high growth rate, and trophic plasticity, H. anomala exhibits a high invasiveness and may strongly alter the food web of Lake Bourget.

Indonesian Small Pelagic Resource Accounting

Fish is one of natural resources, which is important for food security. Small pelagic fish is one of the sources of food, the most widely consumed by people of Indonesia, given the existence of a fairly abundant species, and are found in almost entire territorial waters of Indonesia, and also has a relatively affordable price. Management of pelagic fishery in the waters of Indonesia, thus becomes important, especially to maintain the sustainable industry. Optimal and sustainable fisheries industry can only be achieved with proper planning through the implementation of appropriate management instruments as well. Fisheries resources accounting is one of the planning instruments, which should be used as a main reference of Fisheries Management Plan. In general, fisheries accounting provide insights for policy makers on how the flow of the stocks of fish and its relation to changes in the dynamic of natural and economic activity of fishing. Small pelagic resource accounting is one of the mandates of agenda 21 UNCED recommendation, as formulated in the System of Integrated Environmental and Economic Accounting (SEEA). Besides, this is also a decree of Indonesian Law No. 32/2009 regarding the Management and Environmental protection. The paper discusses the fisheries account, both physical and monetary, for small pelagic fish. By using resource accounting, we can understand the dynamics of the availability of stocks of small pelagic fisheries in Indonesia for the sake of food security. The methods in use is the standard bio-economic modelling, using fox algorithm for parameter estimation, and resource accounting method of the System of National Accounts of FAO[1], adapted to the data existing condition. The results of the analysis, include measurement of standing stocks (physical assets account), fishable biomass, depletion, as well as monetary account. Paper also provides suggestion for management, as well as policy recommendation.Keywords: Small pelagic, Resource Accounting, Physical assets account, monetary account, Fisheries Management Plan, Bio-economic modeling, Policy recommendation.

Facultative paedomorphosis as a mechanism promoting intraspecific niche differentiation

Organisms with complex life cycles are characterized by a metamorphosis that allows for a major habitat shift and the exploitation of alternative resources. However, metamorphosis can be bypassed in some species through a process called paedomorphosis, resulting in the retention of larval traits at the adult stage and is considered important at both micro‐ and macroevolutionary scales. In facultatively paedomorphic populations of newts, some individuals retain gills and a fully aquatic life at the adult stage (paedomorphs), while others undergo complete metamorphosis (metamorphs), allowing for a terrestrial life‐stage. Because facultative paedomorphosis affects trophic structures and feeding mechanism of newts, one hypothesis is that it may be maintained as a trophic polymorphism, with the advantage to lessen intraspecific competition during the shared aquatic life‐stage. Here, we tested this hypothesis combining stomach content data with stable isotope techniques, using carbon and nitrogen stable isotopes, in facultatively paedomorphic alpine newtsIchthyosaura alpestris. Both stomach content and stable isotope analyses showed that paedomorphs had smaller trophic niches and were more reliant on pelagic resources, while metamorphs relied more on littoral resources, corresponding to a polyphenism along the littoral–pelagic axis and the extension of the population's trophic niche to otherwise ‘underused’ pelagic resources by paedomorphs. Interestingly, stable isotopes revealed that the trophic polyphenism was less marked in males than in females and potentially linked to sexual activity. Although paedomorphosis and metamorphosis are primarily seen as results of tradeoffs between the advantages of using aquatic versus terrestrial habitats, this study provides evidence that additional forces, such as intraspecific trophic niche differences between morphs and trophic niche expansion, may play an important role in the persistence of this dimorphism in heterogeneous environments. Moreover, the different patterns found in males and females show the importance of considering sex to understand the evolutionary ecology of trophic polymorphisms.

Variable littoral‐pelagic coupling as a food‐web response to seasonal changes in pelagic primary production

Abstract Lakes are among the most seasonally forced ecosystems on Earth. Seasonal variation in temperature and light produce cyclic patterns in water column mixing, nutrient supply and phytoplankton biomass. Diet responses of consumers to these patterns have rarely been quantified. Moreover, pelagic‐littoral coupling of dietary resources by mobile consumers is commonly considered to be static over annual cycles. This study quantifies littoral‐pelagic diet responses of multiple consumers to a strong shift in pelagic phytoplankton abundance over an annual cycle (September 2014 to August 2015) in a large (area 614 km2), oligotrophic, monomictic lake (Lake Taupō, New Zealand). Intra‐annual patterns in pelagic phytoplankton (chlorophyll a) and zooplankton were determined over multiple years. Major resource and consumer δ13C and δ15N were then collected over an annual cycle. Temporal patterns in food‐web structure were examined using convex hulls as a proxy of community trophic niche size. Diet was quantified using mixing models for zooplankton, meso‐predatory zooplanktivorous common smelt (Retropinna retropinna) and benthivorous common bullies (Gobiomorphus cotidianus), as well as the top‐predator rainbow trout (Oncorhynchus mykiss). Trophic structure patterns for smelt, bullies and trout were then independently examined using compound‐specific amino acid δ15N analyses (CSIA‐AA). Lake Taupō demonstrated similar food‐web patterns to other lakes globally. Phytoplankton and zooplankton demonstrated strong seasonal oscillations of abundance driven by both bottom‐up (nutrient supply) and top‐down (stable limit cycle) drivers. The food web demonstrated the typical nested structure. It responded to seasonally low and high pelagic resource availability periods by expansion and contraction, respectively, of trophic niche space. In response to lower pelagic phytoplankton abundance during summer stratification, and phytoplankton accumulation at a deep chlorophyll maximum (DCM), zooplankton abundance reduced and their diet became dominated by phytoplankton from below the thermocline (i.e. the hypolimnion and DCM). This change may have been prompted by the combined drivers of avoidance of predation and depauperate food supply in surface waters. The diet of smelt and bullies switched from predominantly zooplankton to benthic macroinvertebrates, synchronous with the decline in pelagic zooplankton. Trout diet, inferred from comparison of isotopic signatures of tissues with different turnover rates, also increased littoral resource reliance over the stratified period. Smelt, bully and trout CSIA‐AA data confirmed estimates of trophic position and indicated a greater degree of trophic complexity in the littoral than the pelagic food chain. Food webs in large, deep lakes such as Taupō are expected to be primarily pelagic. This study demonstrates the need to re‐examine this expectation due to seasonal variations in productivity. The relatively small littoral areas in large lakes, combined with meso‐predators’ highly seasonally variable littoral resource use, may drive strong seasonal top‐down effects on littoral macroinvertebrate prey. Our study supports the notion that food‐web interactions are highly dynamic and responsive to seasonal forcing. By linking food‐web dynamics to dynamic environmental conditions, this study provides a framework for future studies research on understanding lake food‐web responses to a range of annual/seasonal and global environmental change drivers.

Strengthening the resilience of small-scale fisheries: A modeling approach to explore the use of in-shore pelagic resources in Melanesia

Small-scale fisheries play a critical role in both poverty alleviation and food security. A large proportion of the world fish stocks are, however, getting fully or over-exploited. In this article we address these issues in the context of the small-scale fisheries of the Solomon Islands. The paper explores the extent to which in-shore Fish Aggregating Devices (FADs) can help increasing the resilience of the small scale fishery system and reconciling social, economic and ecological priorities. Based on the concept of ‘time of crisis’ developed recently in the viability literature, we propose to calculate a resilience index through a dynamic stochastic model calibrated by ethnological observations. The resilience index calculation reveals two major findings: (i) the resilience of the small scale fishery system is currently nonexistent and (ii) the introduction of FADs can improve it. The effects of the FADs' implementation are then discussed in the light of a socio-economic perspective. Such results bring new insights into the question of the future of the small scale fishery sector, especially in relation to the local economy evolution from a barter dominance to a cash oriented economy. At the same time, the current subsistence fisheries seems more resilient in general due to a distributive effects which ease the ‘race for fish behaviors’. Finally, our analysis reveals that while the FADs implementation stands as a short and mid-term answer, demographic drivers are important and other alternatives will need to be considered if the overall viability of the system is to be maintained in the longer-term.

Some like it deep: Intraspecific niche segregation in ruffe (Gymnocephalus cernua)

Abstract Generalist fishes commonly show intraspecific niche segregation along the littoral–pelagic resource axis in lakes. Recent studies have shown that the deep, cold and seemingly unproductive profundal zone can also offer underutilised resources and facilitate specialised individuals, and can contribute to lake food webs via methane‐derived carbon pathways. Despite numerous examples from salmonid fish species, such intraspecific niche segregation along a littoral–profundal resource axis has not been reported in percids or other predominantly littoral benthivorous fishes. Here, we describe a case of ruffe (Gymnocephalus cernua: Percidae) populations consisting of shallow‐ and deep‐water dwelling individuals in two post‐mining lakes in the northern Czech Republic. Results from stable isotope (δ15N and δ13C) mixing models indicated that littoral and profundal food resources dominated the long‐term diets of ruffe individuals caught from shallow‐ and deep‐water habitats, respectively. No similar niche segregation along the littoral–profundal gradient was observed in coexisting perch (Perca fluviatilis: Percidae) which used more pelagic food than the benthivorous ruffe. The observed littoral–profundal niche segregation in ruffe was more pronounced in the macrophyte‐rich and poorly oxygenated Lake Milada, where high habitat complexity and strong interspecific interactions in the littoral zone as well as the absence of competing fish species in the profundal zone likely promote narrow trophic niches of shallow‐ and deep‐water dwelling ruffe Our study provides novel evidence of littoral–profundal niche segregation in a predominantly benthivorous fish species. The results also show that intraspecific niche variation can be affected by lake ecosystem characteristics, in particular by the availability of and competition for littoral and profundal resources. Although more research is needed to confirm potential early divergence of shallow‐ and deep‐water dwelling ruffe as well as cascading effects on lake ecosystem processes (e.g. nutrient cycling and competitive and predatory interactions), our study indicates that individual ruffe may show limited habitat and food‐web coupling due to their restricted use of shallow or deep resources.

Pola Rekrutmen, Mortalitas, dan Laju Eksploitasi Ikan Lemuru (Amblygaster sirm, Walbaum 1792) di Perairan Selat Sunda

Sunda Strait has high potential of pelagic fish resources, one of which is spotted sardinella (Amblygaster sirm). High market demand of spotted sardinella leads to its high exploitation. Management of sustainable used of this species need various biological information of the target species.The aims of this research wereto analyze of therecruitment pattern, mortality, and exploitation rate of spotted sardinella. Sampling was conducted in April to August 2015 from the catchment landed at Labuan Coastal Fishing Port, Banten. Fish samples taken during the study consisted of 527 males and 245 females. The results showed thatpeak recruitment season for spotted sardinella occurs in Maret (11.64%) and July (13.67%).The natural mortality (M), fishing mortality (F), total mortality (Z) for male were 0,33; 5,30; 5,63 year-1 respectively, and for female were 0,51; 7,75;8,27 year-1 respectively. Exploitation rate (E) for male was 0,94 year-1 and for female was 0,93 year-1.Keywords : exploitation, growth, mortality, spotted sardinella, Sunda Strait

Krill distribution in relation to environmental parameters in mesoscale structures in the Ross Sea

Krill, a key pelagic resource of the Antarctic food web, provides an important link between primary and secondary plankton production and top predators. Since krill abundance is a crucial factor in Antarctic ecosystem functioning, its monitoring supplies vital data. Acoustic surveys are an effective approach to estimating krill abundance. An acoustic survey was conducted in the western Ross Sea in January 2014–10years after a similar survey by our team - to estimate krill abundance and biomass and monitor oceanographic conditions. Antarctic krill (Euphausia superba) was detected in the northern part of the western Ross Sea and dense swarms of ice krill (Euphausia crystallorophias) were found in its central coastal area. Data analysis revealed an inverse correlation between E. superba density and salinity in the water column, whereas a positive correlation was found between E. crystallorophias abundance and fluorescence; the latter relationship was confirmed in thematic maps of E. crystallorophias spatial distribution and fluorescence. Comparison of 2004 and 2014 biomass data showed a much greater abundance of both species in the more recent survey.

Temporal variability in assimilation of basal food sources by an omnivorous fish at Patos Lagoon Estuary revealed by stable isotopes (2010–2014)

ABSTRACTEstuarine systems are characterized by complex physicochemical and hydrological changes occurring across multiple scales, which determine spatiotemporal variation in distribution and abundance of consumers and their resources. However, little is known about the effects of these biophysical interactions on the interannual dynamics of estuarine food webs. In this work, a five-year stable isotope data set was used to investigate interannual variability in trophic links between basal production sources (seagrass, macroalgae, saltmarsh, particulate organic matter in suspension and in the sediment) and an omnivorous fish (Jenynsia multidentata) in a subtropical estuary emptying in the Southwestern Atlantic. The isotopic variability (δ13C, δ15N) of basal sources and the consumer was analysed seasonally on a mudflat from 2010 to 2014. Jenynsia multidentata showed significant interannual variation in their trophic links with primary producers. In most seasons and years, the consumer relied heavily on benthic-associated food resources, but shifted to pelagic food resources during certain seasons. A ‘green tide’ caused by a massive bloom of vicariant macroalgae occurred on the mudflat, but our findings suggested that the carbon-derived portion of this basal production source was not assimilated by J. multidentata. Instead, seagrass was the most assimilated benthic basal food source in most seasons and years. These results suggest that the intensity of benthic and pelagic trophic pathways sustaining estuarine consumers are not static, but change in response to intra- and interannual variation in the availability of basal production sources. Our findings reinforce the need to account for interannual trends in availability of resources when modelling estuarine food web dynamics.

Pelagic resources landings in central-southern Chile under the A2 climate change scenarios

Artificial neural networks (ANNs) were used to predict landings of anchovy (Engraulis ringens), common sardine (Strangomera bentincki), and jack mackerel (Trachurus murphyi) in central-southern Chile. Twelve environmental variables were considered along with fishing effort (fe) and landing statistics from 1973 to 2012. During external validation, the best models with all of the selected variables gave r2 values of 90 % for anchovy, 96 % for common sardine, and 88 % for jack mackerel. The models were simplified by considering only fe and sea surface temperature from NCEP/NCAR reanalysis data (SST-NOAA), and very similar fits were achieved (87, 92, and 88 %, respectively). Future SSTs were obtained from the A2 climate change scenario and regionalized using statistical downscaling techniques. The downscaled SSTs were used as input for landings predictions using ANN simplified models. In addition, three scenarios of future fishing efforts (2010–2012 average, average + 50 %, and average − 50 %) were used as the input data for landing simulations. The results of the predictions show a decrease of 9 % in future landings of sardine and an increase of 17 % for jack mackerel when comparing 2015 and 2065 monthly projections. However, no significant differences are shown when comparing the estimated landings for the three fishing effort scenarios. Finally, more integrative and complex conceptual models that consider oceanographic-biophysical, physiological, environmental-resource, and interspecies processes need to be implemented.

Swordfish monitoring by a GIS-based spatial and temporal distribution analysis on harpoon fishery data: A case of study in the central Mediterranean Sea

The Geographic Information Systems (GIS) was used to support fishery analyses aimed to monitor the swordfish harpoon fishing and analyze temporal and spatial patterns of catch distribution, also in relation to the environmental parameter Sea Surface Temperature (SST). The study was carried out in an important reproductive area of the Mediterranean Sea, including the Strait of Messina and nearby areas (south-eastern Tyrrhenian Sea and north-western Ionian sea). These locations also represent the unique fishing ground of the Italian swordfish harpoon fishery.Fishery, environmental and biological data were collected between 2002 and 2011 from fishermen’s logbooks and by observations on-board of fishing vessels during swordfish harpoon fishing season (May to August). Data were organized into a database and structured on a geographical reference to allow a quantitative multi-parameter modelling through the GIS tools.The application of GIS allowed a good visualisation of catch distribution patterns, underlining annual and monthly differences in resource availability to fishery. The analysis of GIS maps showed a change in swordfish behaviour, likely related to SST anomalies and, as a consequence, difference in catch and effort distribution patterns. These differences were more evident if fishes in pair were considered. GIS turned out an important and powerful tool to analyze fishing information; the production of georeferentiated maps helps scientist to an easier interpretation of data on large pelagic resources. The proposed GIS-based analysis can add new information on swordfish and help decision makers in the Mediterranean swordfish management.

Body size is negatively correlated with trophic position among cyprinids.

Body size has many ecological and evolutionary implications that extend across multiple levels of organization. Body size is often positively correlated with species traits such as metabolism, prey size and trophic position (TP) due to physiological and mechanical constraints. We used stable isotope analysis to quantify TP among minnows across multiple assemblages that differed in their species composition, diversity and food web structure. Body size significantly predicted TP across different lineages and assemblages, and indicated a significant negative relationship. The observed negative relationship between body size and TP is contrary to conventional knowledge, and is likely to have arisen owing to highly clade-specific patterns, such that clades consist of either large benthic species or small pelagic species. Cyprinids probably subvert the physiological and mechanical constraints that generally produce a positive relationship between body size and TP using anatomical modifications and by consuming small-bodied prey, respectively. The need for herbivorous cyprinids to digest cellulose-rich foods probably selected for larger bodies to accommodate longer intestinal tracts and thereby to facilitate digestion of nutrient-poor resources, such as algae. Therefore, body size and TP are likely to have coevolved in cyprinids in association with specialization along the benthic to pelagic resource axis.