Spillover from marine protected areas to adjacent fisheries has an ecological and a fishery component

Marine Protected Areas (MPAs), if well designed and managed, can produce conservation benefits to fish assemblages within no-take zones and fishery benefits in neighboring areas through ‘spillover’. However, although plenty of studies have provided evidence of the benefits produced within MPA boundaries, overall benefits to local fisheries, especially via spillover, seem to be still unclear. Because of the lost fishing grounds following an MPA establishment, local fishermen usually oppose MPAs. There is, therefore, the urgent need for a better understanding of the mechanism(s) through which MPAs can export fishable fish biomass towards adjacent fished areas, a process that could counterbalance the loss of fishing grounds. Here we review the literature on spillover for refining the terminology, detailing the underlying mechanisms and identifying both the existing and needed methodological approaches to measure spillover. Operationally, two types of spillover should be considered: ecological spillover (i.e. the net export of juvenile, subadult and adult biomass from MPAs outwards driven by density-dependent processes) and the fishery spillover (i.e. the proportion of this biomass that can be fished, taking into account regulations and accessibility). Underwater visual census and tagging/tracking may allow getting evidence of ecological spillover, while experimental catch data are essential to assess and monitor fishery spillover, which is the main component of MPAs that can provide direct benefit to local fisheries.     

Assessing Dispersal Patterns of Fish Propagules from an Effective Mediterranean Marine Protected Area

Successfully enforced marine protected areas (MPAs) have been widely demonstrated to allow, within their boundaries, the recovery of exploited species and beyond their boundaries, the spillover of juvenile and adult fish. Little evidence is available about the so-called ‘recruitment subsidy’, the augmented production of propagules (i.e. eggs and larvae) due to the increased abundance of large-sized spawners hosted within effective MPAs. Once emitted, propagules can be locally retained and/or exported elsewhere. Patterns of propagule retention and/or export from MPAs have been little investigated, especially in the Mediterranean. This study investigated the potential for propagule production and retention/export from a Mediterranean MPA (Torre Guaceto, SW Adriatic Sea) using the white sea bream, Diplodus sargus sargus, as a model species. A multidisciplinary approach was used combining 1) spatial distribution patterns of individuals (post-settlers and adults) assessed through visual census within Torre Guaceto MPA and in northern and southern unprotected areas, 2) Lagrangian simulations of dispersal based on an oceanographic model of the region and data on early life-history traits of the species (spawning date, pelagic larval duration) and 3) a preliminary genetic study using microsatellite loci. Results show that the MPA hosts higher densities of larger-sized spawners than outside areas, potentially guaranteeing higher propagule production. Model simulations and field observation suggest that larval retention within and long-distance dispersal across MPA boundaries allow the replenishment of the MPA and of exploited populations up to 100 km down-current (southward) from the MPA. This pattern partially agrees with the high genetic homogeneity found in the entire study area (no differences in genetic composition and diversity indices), suggesting a high gene flow. By contributing to a better understanding of propagule dispersal patterns, these findings provide crucial information for the design of MPAs and MPA networks effective to replenish fish stocks and enhance fisheries in unprotected areas.     

Empirical Evidence for Species-Specific Export of Fish Na?veté from a No-Take Marine Protected Area in a Coastal Recreational Hook and Line Fishery

No-take marine protected areas (MPAs) are assumed to enhance fisheries catch via the “spillover” effect, where biomass is exported to adjacent exploited areas. Recent studies in spearfishing fisheries suggest that the spillover of gear-naïve individuals from protected to unprotected sites increases catch rates outside the boundaries of MPAs. Whether this is a widespread phenomenon that also holds for other gear types and species is unknown. In this study, we tested if the distance to a Mediterranean MPA predicted the degree of vulnerability to hook and line in four small-bodied coastal fish species. With the assistance of underwater video recording, we investigated the interaction effect of the distance to the boundary of an MPA and species type relative to the latency time to ingest a natural bait, which was considered as a surrogate of fish naïveté or vulnerability to fishing. Vulnerability to angling increased (i.e., latency time decreased) within and near the boundary of an MPA for an intrinsically highly catchable species (Serranus scriba), while it remained constant for an intrinsically uncatchable control species (Chromis chromis). While all of the individuals of S. scriba observed within the MPA and surrounding areas were in essence captured by angling gear, only one fifth of individuals in the far locations were captured. This supports the potential for the spillover of gear-naïve and consequently more vulnerable fish from no-take MPAs. Two other species initially characterized as intermediately catchable (Coris julis and Diplodus annularis) also had a shorter latency time in the vicinity of an MPA, but for these two cases the trend was not statistically significant. Overall, our results suggest that an MPA-induced naïveté effect may not be universal and may be confined to only intrinsically highly catchable fish species. This fact emphasizes the importance of considering the behavioural dimension when predicting the outcomes of MPAs, otherwise the effective contribution may be smaller than predicted for certain highly catchable species such as S. scriba.     

Spearfishing regulation benefits artisanal fisheries: the ReGS indicator and its application to a multiple-use Mediterranean marine protected area

The development of fishing efficiency coupled with an increase of fishing effort led to the overexploitation of numerous natural marine resources. In addition to this commercial pressure, the impact of recreational activities on fish assemblages remains barely known. Here we examined the impact of spearfishing limitation on resources in a marine protected area (MPA) and the benefit it provides for the local artisanal fishery through the use of a novel indicator. We analysed trends in the fish assemblage composition using artisanal fisheries data collected in the Bonifacio Strait Natural Reserve (BSNR), a Mediterranean MPA where the spearfishing activity has been forbidden over 15% of its area. Fish species were pooled into three response groups according to their target level by spearfishing. We developed the new flexible ReGS indicator reflecting shifts in species assemblages according to the relative abundance of each response group facing external pressure. The catch per unit effort (CPUE) increased by ca. 60% in the BSNR between 2000 and 2007, while the MPA was established in 1999. The gain of CPUE strongly depended on the considered response group: for the highly targeted group, the CPUE doubled while the CPUE of the untargeted group increased by only 15.5%. The ReGS value significantly increased from 0.31 to 0.45 (on a scale between 0 and 1) in the general perimeter of this MPA while it has reached a threshold of 0.43, considered as a reference point, in the area protected from spearfishing since 1982. Our results demonstrated that limiting recreational fishing by appropriate zoning in multiple-use MPAs represents a real benefit for artisanal fisheries. More generally we showed how our new indicator may reveal a wide range of impacts on coastal ecosystems such as global change or habitat degradation.     

The Influence of Data Resolution on Predicted Distribution and Estimates of Extent of Current Protection of Three ‘Listed’ Deep-Sea Habitats

Modelling approaches have the potential to significantly contribute to the spatial management of the deep-sea ecosystem in a cost effective manner. However, we currently have little understanding of the accuracy of such models, developed using limited data, of varying resolution. The aim of this study was to investigate the performance of predictive models constructed using non-simulated (real world) data of different resolution. Predicted distribution maps for three deep-sea habitats were constructed using MaxEnt modelling methods using high resolution multibeam bathymetric data and associated terrain derived variables as predictors. Model performance was evaluated using repeated 75/25 training/test data partitions using AUC and threshold-dependent assessment methods. The overall extent and distribution of each habitat, and the percentage contained within an existing MPA network were quantified and compared to results from low resolution GEBCO models. Predicted spatial extent for scleractinian coral reef and Syringammina fragilissima aggregations decreased with an increase in model resolution, whereas Pheronema carpenteri total suitable area increased. Distinct differences in predicted habitat distribution were observed for all three habitats. Estimates of habitat extent contained within the MPA network all increased when modelled at fine scale. High resolution models performed better than low resolution models according to threshold-dependent evaluation. We recommend the use of high resolution multibeam bathymetry data over low resolution bathymetry data for use in modelling approaches. We do not recommend the use of predictive models to produce absolute values of habitat extent, but likely areas of suitable habitat. Assessments of MPA network effectiveness based on calculations of percentage area protection (policy driven conservation targets) from low resolution models are likely to be fit for purpose.     

The response of phytoplankton community to anthropogenic pressure gradient in the coastal waters of the eastern Adriatic Sea

In order to test the response of phytoplankton to anthropogenic pressure, data of chlorophyll a concentration, phytoplankton abundance, and composition are analyzed in relation to anthropogenic pressure gradient and environmental variables such as temperature, salinity and nutrients. Investigated sites encompassed wide tropic range according to a preliminary determination of anthropogenic pressure, quantified through the LUSI index. Statistical analyses indicated nitrates and silicates as proxies of freshwater influence, and phytoplankton single metrics such as concentrations of chlorophyll a and abundances as indicators of anthropogenic pressure. Boundary values for different water quality classes for coastal waters under indirect freshwater influence (Type II) are obtained according to gradient between concentration of chlorophyll a and pressure index (LUSI), which empirically fit to exponential equation. The response of phytoplankton diversity was not linear, as the highest diversity was observed in the area with intermediate disturbance level. CCA analysis identified Skeletonema marinoii, Scrippsiella trochoidea, Guinardia flaccida, Leptocylindrus spp., Prorocentrum spp., Proboscia alata, Eutreptiella spp., and Pseudonitzschia spp. as local eutrophication indicators, whose abundances increased with nutrients loads.     

Enhancement models at high light intensities

The separate package and spillover models of photosynthetic enhancement are generalized and extended to light saturation assuming hyperbolic or exponential rate versus intensity curves. The available data are more consistent with the exponential model at high light intensities. Two significant conclusions follow: (a) the decreases in enhancement observed at high light intensities are accounted for by the curvatures of the light intensity curves for photosynthesis, and (b) nonlinearity of rate versus intensity curves may be sufficient to reduce enhancement greatly even when the intensity curves appear linear.     

Using Tournament Angler Data to Rapidly Assess the Invasion Status of Alien Sport Fishes (Micropterus spp.) in Southern Africa

Fishes are one of the most commonly introduced aquatic taxa worldwide, and invasive fish species pose threats to biodiversity and ecosystem function in recipient waters. Considerable research efforts have focused on predicting the invasibility of different fish taxa; however, accurate records detailing the establishment and spread of invasive fishes are lacking for large numbers of fish around the globe. In response to these data limitations, a low-cost method of cataloging and quantifying the temporal and spatial status of fish invasions was explored. Specifically, angler catch data derived from competitive bass angling tournaments was used to document the distribution of 66 non-native populations of black bass (Micropterus spp.) in southern Africa. Additionally, catch data from standardized tournament events were used to assess the abundance and growth of non-native bass populations in southern Africa relative to their native distribution (southern and eastern United States). Differences in metrics of catch per unit effort (average number of fish retained per angler per day), daily bag weights (the average weight of fish retained per angler), and average fish weight were assessed using catch data from 14,890 angler days of tournament fishing (11,045 days from South Africa and Zimbabwe; 3,845 days from the United States). No significant differences were found between catch rates, average daily bag weight, or the average fish weight between countries, suggesting that bass populations in southern Africa reach comparable sizes and numbers relative to waters in their native distribution. Given the minimal cost associated with data collection (i.e. records are collected by tournament organizers), the standardized nature of the events, and consistent bias (i.e. selection for the biggest fish in a population), the use of angler catch data represents a novel approach to infer the status and distribution of invasive sport fish.     

Spatial distribution and diversity of commercial demersal fish species in the shelf waters of the Caspian Sea

The Caspian Sea (CS) is a unique ecosystem known for its several fish species, especially sturgeons. To exhaustively manage the fish stocks of this ecosystem, detailed knowledge of species composition, abundance, distribution, and the habitat traits of the living organisms is necessary. This study analyzed the diversity, spatial, and seasonal distribution of commercial demersal fish species, and examined the relationships between community structure and environmental variability in Iranian shelf waters of the CS. For this purpose, seasonally fish sampling took place between 2009 and 2011 with a bottom trawl. Among 11 fish species captured, Chelon spp., Rutilus kutum, and Vimba vimba showed the highest abundances (i.e. 88.49%, 10.67%, and 0.69%, respectively). Univariate and multivariate analyses showed differences in commercial fish assemblages (abundance and species richness) according to seasons and regions. Distance-based Linear Model (DisTLM) showed that eight environmental variables display significant linear relationships with the fauna resemblance matrix (p < .05). Based on AIC criteria, the combination of silt&clay, TOM, longitude, depth, bottom, and surface temperature used to build the parsimonious DisTLM model explain 67.03% of the total variability. The results revealed a biogeographical and temporal gradient from the west to the east and summer to winter, in terms of commercial demersal fish assemblages and species diversity, as a consequence of different geomorphological, bottom substratum conditions and benthic communities.     

青弋江鱼类分类群和功能群的α和β多样性纵向梯度格局

确定溪流鱼类多样性的时空分布格局可为鱼类多样性保护与管理提供科学基础。尽管溪流鱼类分类群多样性的纵向梯度格局已有大量报道, 但以鱼类生物学特征为基础的功能多样性研究较少。本文基于2009-2010年4个季度对青弋江1-5级溪流共15个样点的调查数据, 利用形态特征数据和食性构建了鱼类复合功能群, 研究了不同级别溪流间鱼类分类群和功能群组成及多样性的异同, 着重探讨了鱼类分类群和功能群的α和β多样性沿溪流纵向梯度的变化规律。采集到的56种鱼类可分为4个营养功能群和5个运动功能群, 共计14个“营养-运动”复合功能群。双因素交互相似性分析结果显示, 鱼类分类群和功能群组成都随河流级别显著变化, 但季节动态不显著; 双因素方差分析后发现, 鱼类分类群和功能群α、β多样性都随河流级别显著变化, 但受季节影响不显著。经回归分析, 分类群和功能群α多样性与河流级别大小呈显著的线性正相关, 但最大分类群α多样性出现于4级河流, 最大功能群α多样性在4级和5级河流间一致; 分类群和功能群β多样性与河流级别大小呈显著的二项式关系, 呈U型分布。分类群β多样性的空间变化主要取决于物种周转, 而功能群β多样性主要由嵌套所驱动。本研究表明, 沿着“上游-下游”的纵向梯度, 河流鱼类的α和β多样性的空间变化规律不同, 分类群和功能群α多样性的空间格局基本一致, 但分类群(主要是物种周转)和功能群β多样性(主要是功能嵌套)的空间变化过程的驱动机制不同。     

Fish with Chips: Tracking Reef Fish Movements to Evaluate Size and Connectivity of Caribbean Marine Protected Areas

Coral reefs and associated fish populations have experienced rapid decline in the Caribbean region and marine protected areas (MPAs) have been widely implemented to address this decline. The performance of no-take MPAs (i.e., marine reserves) for protecting and rebuilding fish populations is influenced by the movement of animals within and across their boundaries. Very little is known about Caribbean reef fish movements creating a critical knowledge gap that can impede effective MPA design, performance and evaluation. Using miniature implanted acoustic transmitters and a fixed acoustic receiver array, we address three key questions: How far can reef fish move? Does connectivity exist between adjacent MPAs? Does existing MPA size match the spatial scale of reef fish movements? We show that many reef fishes are capable of traveling far greater distances and in shorter duration than was previously known. Across the Puerto Rican Shelf, more than half of our 163 tagged fish (18 species of 10 families) moved distances greater than 1 km with three fish moving more than 10 km in a single day and a quarter spending time outside of MPAs. We provide direct evidence of ecological connectivity across a network of MPAs, including estimated movements of more than 40 km connecting a nearshore MPA with a shelf-edge spawning aggregation. Most tagged fish showed high fidelity to MPAs, but also spent time outside MPAs, potentially contributing to spillover. Three-quarters of our fish were capable of traveling distances that would take them beyond the protection offered by at least 40–64% of the existing eastern Caribbean MPAs. We recommend that key species movement patterns be used to inform and evaluate MPA functionality and design, particularly size and shape. A re-scaling of our perception of Caribbean reef fish mobility and habitat use is imperative, with important implications for ecology and management effectiveness.     

A generalized spatial niche model for aquatic macrophytes

The spatial niches of submerged macrophytes and some relevant statistics for niche extensions and boundaries are described. An interpretation of the potential niche as a probability measure of survival over an n-dimensional gradient space is given. To this end a set of probability measure of is introduced. It is shown that these measures closely relate to statistical concepts found in survival and failure time analysis. By this approach, potential niches are wholly defined as a statistical concept. Realized niches then arise as samples from the specified statistical model: hence appropriate niche location and size measures can be derived.The conceptualized model of the survival niche extends to a general model which describes the shape of realized spatial niches for aquatic macrophytes. This general model was derived from actual vegetation data sampled by diving in many Norwegian lakes. Spatial performance on the vertical gradient can be described by a product of doubly exponential functions. Each of these corresponds to a Gumbel EV1 distribution and expresses the probability distribution of the species' up- and downslope niche boundaries, respectively. Theoretically, both potential and realized niches separate into a persistent and a transient region, each related to ddifferent time scales. The deep-water patchiness, commonly observed for submerged macrophytes, might indicate the transient domain of a realized niche. Published data indicate that the proposed model had widespread applicability, and also relevance to, for example, periphyton.     

Monitoring Spawning Activity in a Southern California Marine Protected Area Using Molecular Identification of Fish Eggs

In order to protect the diverse ecosystems of coastal California, a series of marine protected areas (MPAs) have been established. The ability of these MPAs to preserve and potentially enhance marine resources can only be assessed if these habitats are monitored through time. This study establishes a baseline for monitoring the spawning activity of fish in the MPAs adjacent to Scripps Institution of Oceanography (La Jolla, CA, USA) by sampling fish eggs from the plankton. Using vertical plankton net tows, 266 collections were made from the Scripps Pier between 23 August 2012 and 28 August 2014; a total of 21,269 eggs were obtained. Eggs were identified using DNA barcoding: the COI or 16S rRNA gene was amplified from individual eggs and sequenced. All eggs that were successfully sequenced could be identified from a database of molecular barcodes of California fish species, resulting in species-level identification of 13,249 eggs. Additionally, a surface transport model of coastal circulation driven by current maps from high frequency radar was used to construct probability maps that estimate spawning locations that gave rise to the collected eggs. These maps indicated that currents usually come from the north but water parcels tend to be retained within the MPA; eggs sampled at the Scripps Pier have a high probability of having been spawned within the MPA. The surface transport model also suggests that although larvae have a high probability of being retained within the MPA, there is also significant spillover into nearby areas outside the MPA. This study provides an important baseline for addressing the extent to which spawning patterns of coastal California species may be affected by future changes in the ocean environment.     

The fish zonation of the Itanhaém river basin in the Atlantic Forest of southeast Brazil

The distribution range of fishes along an upstream–downstream gradient within a river basin is determined by the ecological requirements of each fish species. This differential pattern of distribution may suggest the occurrence of fish zones, where different functional guilds would prevail. The earliest concept of fish zonation highlighted the preferential position of several species in European rivers. Nowadays, there is a consensus that for a broad application of this concept, it is necessary to consider the division in functional groups along the downstream profile as related to reproductive, feed and population dynamics traits. However, for a number of tropical systems, such information does not exist. In this case, it is possible to use the fish family as a surrogate metric, by assuming that it fully covers common aspects of morphology, feeding, and behavior. Using this surrogate metric, we analyzed the distribution range of fish species along an elevation gradient in a typical Atlantic Forest basin in southeast Brazil. Our objective was to delimit fish zones based on the representativeness of some dominant fish families. Between 2006 and 2008, we sampled 42 sites from the estuary to the headwater creeks in elevations that varied from 3 to 783 m. The data were explored using the species (or family) occurrence, relative numerical abundance (N′), relative biomass (B′), and the importance index (IP). We applied the non-metric multidimensional scaling (NMDS) to ordinate the sampling sites using the Jaccard distance calculated on the species occurrence matrix. Data on family importance were superimposed to the NMDS to check how the distribution and the abundance of the families were correlated to the ordination. We caught 64 species distributed among 25 fish families. Based on the dominance of some families, we propose that the fish assemblage in the Itanhaém river basin can be organized in four fish zones (FZ) and three transitory zones (TZ), which replace each other along the longitudinal gradient. The marine/estuarine fishes dominated in FZ1 and TZ1. The freshwater fishes were dominated by Characidae (FZ2), Heptapteridae (FZ3), and Gymnotidae (FZ4). TZ2 was equally dominated by Characidae, Loricariidae, and Heptapteridae. The distinct assemblage composition along the FZ’s may relate to complex interactions involving seasonal patterns of variation in salinity levels (next to estuary), slope, presence of downstream barriers, and availability of food resources. We expect that the patterns observed in our study will also be presented in other coastal Atlantic Forest basins in Southeast Brazil.     

Adaptive radiation within marine anisakid nematodes: a zoogeographical modeling of cosmopolitan, zoonotic parasites

Parasites of the nematode genus Anisakis are associated with aquatic organisms. They can be found in a variety of marine hosts including whales, crustaceans, fish and cephalopods and are known to be the cause of the zoonotic disease anisakiasis, a painful inflammation of the gastro-intestinal tract caused by the accidental consumptions of infectious larvae raw or semi-raw fishery products. Since the demand on fish as dietary protein source and the export rates of seafood products in general is rapidly increasing worldwide, the knowledge about the distribution of potential foodborne human pathogens in seafood is of major significance for human health. Studies have provided evidence that a few Anisakis species can cause clinical symptoms in humans. The aim of our study was to interpolate the species range for every described Anisakis species on the basis of the existing occurrence data. We used sequence data of 373 Anisakis larvae from 30 different hosts worldwide and previously published molecular data (n = 584) from 53 field-specific publications to model the species range of Anisakis spp., using a interpolation method that combines aspects of the alpha hull interpolation algorithm as well as the conditional interpolation approach. The results of our approach strongly indicate the existence of species-specific distribution patterns of Anisakis spp. within different climate zones and oceans that are in principle congruent with those of their respective final hosts. Our results support preceding studies that propose anisakid nematodes as useful biological indicators for their final host distribution and abundance as they closely follow the trophic relationships among their successive hosts. The modeling might although be helpful for predicting the likelihood of infection in order to reduce the risk of anisakiasis cases in a given area.     

Environmental DNA as a ‘Snapshot’ of Fish Distribution: A Case Study of Japanese Jack Mackerel in Maizuru Bay,Sea of Japan

Recent studies in streams and ponds have demonstrated that the distribution and biomass of aquatic organisms can be estimated by detection and quantification of environmental DNA (eDNA). In more open systems such as seas, it is not evident whether eDNA can represent the distribution and biomass of aquatic organisms because various environmental factors (e.g., water flow) are expected to affect eDNA distribution and concentration. To test the relationships between the distribution of fish and eDNA, we conducted a grid survey in Maizuru Bay, Sea of Japan, and sampled surface and bottom waters while monitoring biomass of the Japanese jack mackerel (Trachurus japonicus) using echo sounder technology. A linear model showed a high R² value (0.665) without outlier data points, and the association between estimated eDNA concentrations from the surface water samples and echo intensity was significantly positive, suggesting that the estimated spatial variation in eDNA concentration can reflect the local biomass of the jack mackerel. We also found that a best-fit model included echo intensity obtained within 10–150 m from water sampling sites, indicating that the estimated eDNA concentration most likely reflects fish biomass within 150 m in the bay. Although eDNA from a wholesale fish market partially affected eDNA concentration, we conclude that eDNA generally provides a ‘snapshot’ of fish distribution and biomass in a large area. Further studies in which dynamics of eDNA under field conditions (e.g., patterns of release, degradation, and diffusion of eDNA) are taken into account will provide a better estimate of fish distribution and biomass based on eDNA.     

Anti-Anisakis IgE Seroprevalence in the Healthy Croatian Coastal Population and Associated Risk Factors

Background

The main objective of the study was to determine the degree of sensitization to Anisakis spp. antigens in healthy coastal population of Dalmatia given the high thermally unprocessed fish intake rate present in this area, suggested as a significant risk factor for anisakiasis. We performed a monocenter, cross-sectional pilot study stratified by geographic area of residence, conducted at the County secondary healthcare provider Medicine-biochemical Laboratory in Split (Croatia), from November 2010 till December 2011, on 500 unpaid volunteer subjects undergoing routine blood analysis and belonging to the south coast of the Adriatic Sea.

Methodology/Principal Findings

We studied the IgE seroprevalence to Anisakis spp. Ani s l and Ani s 7 allergens by indirect ELISA in healthy subjects, which were selected at random in the region of Dalmatia (Southern Croatia), among islands, coastal urban and inland rural populations. In order to detect possible cross-reactivity to other human helminthes, serum samples were tested also for the presence of IgG antibodies to Ascaris lumbricoides and Toxocara canis. The overall and coastal Anisakis seroprevalences for the sampled population were 2% and 2.5%, respectively. The logistic univariate regression analysis confirmed that regarding anti-Anisakis IgE seroprevalence, raw fish intake, daily fish intake, homemade origin of fish dish and occupational contact (professional, artisanal or hobby contact with fishery or fish industry) were risk factors associated to Anisakis spp. sensitization, but neither of the variables was exclusive for a particular seropositive population. Also, a significant difference was observed between seropositive and seronegative subjects that had stated allergy or symptoms associated with allergy (atopic dermatitis, asthma or rhinitis) in their previous history.

Conclusions/Significance

Being the first in Croatia, our study underlines the necessity of incorporating Anisakis spp. allergens in routine hypersensitivity testing of coastal population.     

Uncovering Patterns of Inter-Urban Trip and Spatial Interaction from Social Media Check-In Data

The article revisits spatial interaction and distance decay from the perspective of human mobility patterns and spatially-embedded networks based on an empirical data set. We extract nationwide inter-urban movements in China from a check-in data set that covers half a million individuals within 370 cities to analyze the underlying patterns of trips and spatial interactions. By fitting the gravity model, we find that the observed spatial interactions are governed by a power law distance decay effect. The obtained gravity model also closely reproduces the exponential trip displacement distribution. The movement of an individual, however, may not obey the same distance decay effect, leading to an ecological fallacy. We also construct a spatial network where the edge weights denote the interaction strengths. The communities detected from the network are spatially cohesive and roughly consistent with province boundaries. We attribute this pattern to different distance decay parameters between intra-province and inter-province trips.     

Age‐specific habitat preference,carrying capacity,and landscape structure determine the response of population spatial variability to fishing‐driven age truncation

1. Understanding the mechanisms underlying spatial variability of exploited fish is critical for the sustainable management of fish stocks. Empirical studies suggest that size‐selective fishing can elevate fish population spatial variability (i.e., more heterogeneous distribution) through age truncation, making the population less resilient to changing environment. However, species differ in how their spatial variability responds to age truncation and the underlying mechanisms remain unclear.
2. We hypothesize that age‐specific habitat preference, together with environmental carrying capacity and landscape structure, determines the response of population spatial variability to fishing‐induced age truncation. To test these hypotheses, we design an individual‐based model of an age‐structured fish population on a two‐dimensional landscape under size‐selective fishing. Individual fish reproduces and survives, and moves between habitats according to age‐specific habitat preference and density‐dependent habitat selection.
3. Population spatial variability elevates with increasing age truncation, and the response is stronger for populations with stronger age‐specific habitat preference. On a gradient landscape, reducing carrying capacity elevates the relative importance of density dependence in habitat selection, which weakens the response of spatial variability to age truncation for populations with strong age‐specific habitat preference. On a fragmented landscape, both populations with strong and weak age‐specific habitat preferences are restricted at local optimal habitats, and reducing carrying capacity weakens the responses of spatial variability to age truncation for both populations.
4. Synthesis and applications. We demonstrate that to track and predict the changes in population spatial variability under exploitation, it is essential to consider the interactive effects of age‐specific habitat preference, carrying capacity, and landscape structure. To improve spatial management in fisheries, it is crucial to enhance empirical and theoretical developments in the methodology to quantify age‐specific habitat preference of marine fish, and to understand how climatic change influences carrying capacity and landscape continuity.