Habitat Suitability Index Research Articles

Modeling the Oceanographic Impacts on the Spatial Distribution of Common Cephalopods During Autumn in the Yellow Sea

The importance of the role of cephalopods in marine ecosystems and commercial fisheries has increased over recent years. There is now evidence that the distribution of cephalopods is expanding latitudinally. Nevertheless, information about the spatial distribution of cephalopods and its implications in the Yellow Sea (YS) is not well known. In an attempt to redress this deficiency we firstly conducted a simple analysis of geospatial patterns in fishing effort in the YS during 2012–2016 to ascertain if changes in fishing intensity (across all species) might be responsible for creating an apparent latitudinal shift in cephalopod distribution. Although fishing intensity increased in the YS over the five-year period, there are no significant differences among years within each latitude, implying that all latitudes respond in a similar way each year. We then used long-term scientific survey data (2000, 2009, 2014, and 2017) of cephalopods (Todarodes pacificus, Loliolus spp, Octopus variabilis, Octopus ocellatus, Sepiola birostrata, and Euprymna spp) collected each October in the YS, combined with oceanographic variables including sea surface temperature (SST) and chlorophyll-a concentration (CHLA), to model relationships to establish habitat suitability indices (HSI) using both an arithmetic mean method (AMM) and a geometric mean method (GMM). Cross-validation, standard deviation and mean squared error of prediction (MSEP) were used to evaluate the performance of the HSI. Abundance index data from surveys of 2018 were overlaid on maps of predicted HSI for the same year to visualize the correspondence of the modelled HSI. Spatio-temporal mapping of oceanographic variables showed that SST and CHLA change dramatically around 34°N, which may relate to the spatial distribution of cephalopods. CHLA is the most important oceanographic variable for most squid and octopus species while SST is the most important for bobtail squid. The MSEP showed that the AMM-based HSI performed better than the GMM-based HSI. Future studies should take weighting of oceanographic variables into account and ideally integrate them into a more holistic model to obtain increased precision in predictions when establishing HSI.

Habitat suitability response to sea-level height changes: Implications for Ommastrephid squid conservation and management

Sea level rise, amplified by anthropogenic climate change, causes visible impacts on wildlife habitats in low-lying coastal areas. However, the potential consequences of sea level height (SLH) changes for pelagic fish habitats in the open oceans are poorly understood, especially for climate-sensitive Ommastrephid squid. In this study, the impacts of SLH changes were estimated under three different SLH change scenarios (5 cm, 20 cm, and 35 cm) for the western stock of winter-spring neon flying squid Ommastrephes bartramii, an ecologically- and commercially-important species in the northwest Pacific Ocean (NWPO). A habitat suitability index (HSI) modeling approach was applied to predict the habitat suitability of O. bartramii, using data from 2006 to 2014 for model construction and data from 2015 for model validation. Results showed that the decreasing catch-per-unit-effort (CPUE) of O. bartramii from 2006 to 2015 was highly correlated with the increases in sea level height (SLH). Significant positive relationships were found between the HSI values for latitudinal centers of gravity (LATGHSI) and SLH. The monthly-averaged HSI of O. bartramii was negatively correlated with the SLH, except in July and November. SLH scenarios revealed that the predicted suitable habitat (areas with HSI≥0.6) exhibited a decreasing trend with increasing SLH from August to October. In July and November, the suitable habitat initially increased in the +5 cm and +20 cm scenarios, but largely declined under the +35 cm scenario. The poor habitat (areas with HSI≤0.2) significantly increased under all SLH scenarios. A poleward shift of LATGHSI was observed under all scenarios. These findings suggest that the O. bartramii habitats in the NWPO are at risk to SLH changes and have important implications for better conservation and fishery management regarding pelagic short-lived Ommastrephid squid in global oceans.

Spatial Analysis of Potential Nesting Habitat for Florida Sandhill Cranes

AbstractThe Florida sandhill crane Antigone canadensis pratensis is designated as threatened by the state of Florida, where there is an urgent need to map and quantify available habitat. First, we used habitat suitability index (HSI) modelling to map and assess potential nesting habitat for sandhill cranes in Florida. Second, we used spatial optimization approaches to calculate the maximum number of breeding pairs that can simultaneously occupy potential nests given that they both must be of some minimum quality and must be spaced some minimal distance apart. Mapping results reveal that nesting habitat is concentrated in the central portion of the state, with adequate brooding habitat appearing to be the most limiting factor affecting habitat suitability. Assuming nesting only occurs in habitat rated as high quality (HSI ≥ 0.7) and spacing between adjacent nests is ≥1,000 m, we conservatively estimate that 5,540 nesting pairs of Florida sandhill cranes can potentially be supported. Additional nesting pairs may be supported in habitats of marginal (HSI ≥ 0.3; 14,530) to moderate (HSI ≥ 0.5; 8,723) quality. The suitability maps and breeding pair estimates can be used to identify important habitat areas to focus crane conservation efforts, determine potentially limiting habitat features across the landscape, and potentially guide future population monitoring efforts. For example, grassland or prairie restoration could be used to potentially increase nesting pairs in the southern portion of the state where emergent wetlands are abundant but brooding habitat is lacking.

Effect of Probability Distribution-Based Physical Habitat Suitability Index on Environmental-Flow Estimation

Habitat suitability index (HSI) is a fundamental factor in ecological river-restoration projects for assessing fish habitat to create inhabited environment for aquatic organisms. An accurate estimation of HSI requires long-term-monitored data including flow velocity, water depth, and bed materials; however, this is not easy to collect, and the dataset comprises local characteristics. Therefore, it is difficult to present a generalized method of HSI estimation with limited local and temporal data. In this study, the probability distribution was applied for HSI estimation with limited data measured in the tributaries of Han and Geum Rivers in South Korea. Log-normal distributions were applied to the water depth and velocity data of aquatic habitat for Zacco platypus, and then the developed log-normal distributions were used as the HSI. The HSIs developed by applying the log-normal distribution were compared with the HSIs developed using the instream flow and aquatic system group (IFASG) method. By using the log-normal-distribution-based HSIs, the environmental flows estimated through the physical-habitat-assessment models based on instream flow incremental methodology were also compared with the IFASG-based results. The environmental flows were determined to be similar within an optimal range in both cases of the tributaries of Han and Geum Rivers.

A Migration Model to Predict the Distribution of Scottish Herring and Mackerel

To identify climate-related habitat changes and variations in abundance and distribution of herring and mackerel around the waters of Scotland, a new habitat suitability index (HSI) model and Markov Model were developed in this study. The study only used the distribution of annual catch and fishing efforts. The suitability index (SI) was constructed by newly defined estimate-catch-per-unit-effort (ECPUE). Through the voting method and data of sea surface temperature (SST), the habitat suitability index model (HSI) was established. Based on the HSI, Markov Model was established to predict the movement of shoals. Using the predicted data of future SST, this model can simulate the changes of fish distribution.

Development and evaluation of habitat suitability models for nesting white-headed woodpecker (Dryobates albolarvatus) in burned forest.

Salvage logging in burned forests can negatively affect habitat for white-headed woodpeckers (Dryobates albolarvatus), a species of conservation concern, but also meets socioeconomic demands for timber and human safety. Habitat suitability index (HSI) models can inform forest management activities to help meet habitat conservation objectives. Informing post-fire forest management, however, involves model application at new locations as wildfires occur, requiring evaluation of predictive performance across locations. We developed HSI models for white-headed woodpeckers using nest sites from two burned-forest locations in Oregon, the Toolbox (2002) and Canyon Creek (2015) fires. We measured predictive performance by developing one model at each of the two locations and quantifying discrimination of nest from reference sites at two other wildfire locations where the model had not been developed (either Toolbox or Canyon Creek, and the Barry Point Fire [2011]). We developed and evaluated Maxent models based on remotely sensed environmental metrics to support habitat mapping, and weighted logistic regression (WLR) models that combined remotely sensed and field-collected metrics to inform management prescriptions. Both Maxent and WLR models developed either at Canyon Creek or Toolbox performed adequately to inform management when applied at the alternate Toolbox or Canyon Creek location, respectively (area under the receiver-operating-characteristic curve [AUC] range = 0.61-0.72) but poorly when applied at Barry Point (AUC = 0.53-0.57). The final HSI models fitted to Toolbox and Canyon Creek data quantified suitable nesting habitat as severely burned or open sites adjacent to lower severity and closed canopy sites, where foraging presumably occurs. We suggest these models are applicable at locations similar to development locations but not at locations resembling Barry Point, which were characterized by more (pre-fire) canopy openings, larger diameter trees, less ponderosa pine (Pinus ponderosa), and more juniper (Juniperus occidentalis). Considering our results, we recommend caution when applying HSI models developed at individual wildfire locations to inform post-fire management at new locations without first evaluating predictive performance.

Preferensi Habitat dan Distribusi Spasial Yuwana Rajungan (Portunus pelagicus) di Perairan Pesisir Lampung Timur, Provinsi Lampung

Information on habitat preferences of the blue swimming crab (BSC) juvenile and its spatial distribution is one of the factors behind the successfulness of its sustainable management. This information is needed to provide input for management strategy by considering juvenile crabs and their habitat as important aspect. The purpose of this study is to elucidate habitat preferences, abundance and biomass distribution of BSC juvenile in the east Lampung coastal waters. The research was conducted in September-October 2018, which was located in east Lampung coastal waters, Province Lampung. Spatial distribution through estimation of abundance and biomass of BSC juvenile were relatively high and concentrated in the Gambas and Wako regions at stratification of 2-4 miles from the coastline. The BSC juvenile does not appear to have a high preference to the Kuala Penet coastal habitat condition; it is considered because of low value of abundance, biomass, and Habitat suitability index (HSI). The value of HSI in the Kuala Penet Coastal region is also lower than other locations due to abiotic and biotic factors for supporting the crabs at juvenile stage.

Predicting bycatch hotspots based on suitable habitat derived from fishery-independent data

Bycatch remains a global problem in managing sustainable fisheries. A critical aspect of management is understanding the timing and spatial extent of bycatch. Fisheries management often relies on observed bycatch data, which are not always available due to a lack of reporting or observer coverage. Alternatively, analyzing the overlap in suitable habitat for the target and non-target species can provide a spatial management tool to understand where bycatch interactions are likely to occur. Potential bycatch hotspots based on suitable habitat were predicted for cuskBrosme brosmeincidentally caught in the Gulf of Maine American lobsterHomarus americanusfishery. Data from multiple fisheries-independent surveys were combined in a delta-generalized linear mixed model to generate spatially explicit density estimates for use in an independent habitat suitability index. The habitat suitability indices for American lobster and cusk were then compared to predict potential bycatch hotspot locations. Suitable habitat for American lobster has increased between 1980 and 2013 while suitable habitat for cusk decreased throughout most of the Gulf of Maine, except for Georges Basin and the Great South Channel. The proportion of overlap in suitable habitat varied interannually but decreased slightly in the spring and remained relatively stable in the fall over the time series. As Gulf of Maine temperatures continue to increase, the interactions between American lobster and cusk are predicted to decline as cusk habitat continues to constrict. This framework can contribute to fisheries managers’ understanding of changes in habitat overlap as climate conditions continue to change and alter where bycatch interactions could occur.

Ecohydraulic model development and application: Evaluating the habitats and population of rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and flannelmouth sucker (Catostomus latipinnis) in Colorado River

Ecohydraulics often requires the use of advanced numerical models and ecological theories, which are used for river and aquatic organism management. In this study, a 2D ecohydraulic model system was proposed and used to evaluate the habitat suitability index, weighted useable areas, overall suitability index, fish population number, and fish population density of Colorado River. The 2D ecohydraulic model system comprised hydrodynamic, hydromorphology, habitat, and population models. Three fish species were selected as target fish, which included rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and flannelmouth sucker (Catostomus latipinnis). Five computational domains of the Colorado River were selected for the ecohydraulic model. The surveyed fish data from 2000 to 2009 were used to calibrate the model system. Results indicated that the predicted fish number showed a good agreement with the surveyed fish. It is indicated that the rainbow trout and brown trout fish number showed decreasing trends from 2000 to 2009, while flannelmouth sucker showed increasing trend from 2000 to 2009. The proposed approach demonstrates that the ecohydraulic model system can be used to accurately simulate the river habitat quality and population status. The ecohydraulic model can be an efficient tool to improve understanding of the different scenarios and to assistant for multiple fish habitat and population prediction in river system. It can also provide decision-makers with valuable information to optimize their management.

Optimization of environmental variables in habitat suitability modeling for mantis shrimp Oratosquilla oratoria in the Haizhou Bay and adjacent waters

Habitat suitability index (HSI) models have been widely used to analyze the relationship between species abundance and environmental factors, and ultimately inform management of marine species. The response of species abundance to each environmental variable is different and habitat requirements may change over life history stages and seasons. Therefore, it is necessary to determine the optimal combination of environmental variables in HSI modelling. In this study, generalized additive models (GAMs) were used to determine which environmental variables to be included in the HSI models. Significant variables were retained and weighted in the HSI model according to their relative contribution (%) to the total deviation explained by the boosted regression tree (BRT). The HSI models were applied to evaluate the habitat suitability of mantis shrimp Oratosquilla oratoria in the Haizhou Bay and adjacent areas in 2011 and 2013–2017. Ontogenetic and seasonal variations in HSI models of mantis shrimp were also examined. Among the four models (non-optimized model, BRT informed HSI model, GAM informed HSI model, and both BRT and GAM informed HSI model), both BRT and GAM informed HSI model showed the best performance. Four environmental variables (bottom temperature, depth, distance offshore and sediment type) were selected in the HSI models for four groups (spring-juvenile, spring-adult, fall-juvenile and fall-adult) of mantis shrimp. The distribution of habitat suitability showed similar patterns between juveniles and adults, but obvious seasonal variations were observed. This study suggests that the process of optimizing environmental variables in HSI models improves the performance of HSI models, and this optimization strategy could be extended to other marine organisms to enhance the understanding of the habitat suitability of target species.

Spatial Habitat Suitability Models of Mangroves with Kandelia obovata

Mangrove forests provide important estuarine ecosystem services but are threatened by rising sea levels and anthropogenic impacts. Understanding the habitat characteristics required for mangrove growth is significant for mangrove restoration and integrated management. This study aims to build spatial habitat suitability index (HSI) models for Kandelia obovata mangrove trees. Biological and habitat-related environmental data were collected in the Wazwei and Guandu wetlands in northern Taiwan. We adopted inundation frequency, soil sorting coefficient, and water salinity as the key environmental factors to build HSI models. The dependent variable of these environmental factors was the mangrove biomass per unit area. Significant differences were found for the mangrove biomass on different substrata and shore elevations. The tidal creek had the lowest elevation, and mangrove areas were found at the highest elevations. The oxidization level of the substrate under mangrove forests was high, indicating that the root system of mangroves could carry oxygen into the soil and result in oxidation. Human activities were found to lead to the reduced growth conditions of mangroves. The validation of the HSI model, considering the inundation frequency and soil sorting coefficient, proved to be reliable, with an accuracy ranging from 78% to 90%. A better simulation was found after revising the model by incorporating the factor of water salinity. The model forecast of the mangrove responses to the sea-level rise indicated an increase in the inundation frequency and thus an induced shift and shrinkage of the mangrove area. The increased HSI values of the bare mudflat area demonstrate an option for the potential restoration of mangrove trees. Given the findings of this study, we concluded that mangroves could spread from estuaries to upstream areas due to rising sea levels and might be limited by humanmade impacts. Restoring degraded floodplains is suggested for mangrove habitat rehabilitation.

Relationships between survival and habitat suitability of semi-aquatic mammals.

Spatial distribution and habitat selection are integral to the study of animal ecology. Habitat selection may optimize the fitness of individuals. Hutchinsonian niche theory posits the fundamental niche of species would support the persistence or growth of populations. Although niche‐based species distribution models (SDMs) and habitat suitability models (HSMs) such as maximum entropy (Maxent) have demonstrated fair to excellent predictive power, few studies have linked the prediction of HSMs to demographic rates. We aimed to test the prediction of Hutchinsonian niche theory that habitat suitability (i.e., likelihood of occurrence) would be positively related to survival of American beaver (Castor canadensis), a North American semi‐aquatic, herbivorous, habitat generalist. We also tested the prediction of ideal free distribution that animal fitness, or its surrogate, is independent of habitat suitability at the equilibrium. We estimated beaver monthly survival probability using the Barker model and radio telemetry data collected in northern Alabama, United States from January 2011 to April 2012. A habitat suitability map was generated with Maxent for the entire study site using landscape variables derived from the 2011 National Land Cover Database (30‐m resolution). We found an inverse relationship between habitat suitability index and beaver survival, contradicting the predictions of niche theory and ideal free distribution. Furthermore, four landscape variables selected by American beaver did not predict survival. The beaver population on our study site has been established for 20 or more years and, subsequently, may be approaching or have reached the carrying capacity. Maxent‐predicted increases in habitat use and subsequent intraspecific competition may have reduced beaver survival. Habitat suitability‐fitness relationships may be complex and, in part, contingent upon local animal abundance. Future studies of mechanistic SDMs incorporating local abundance and demographic rates are needed.

Adapting a multi‐species tool for single‐species impact assessments: Managing fishes at risk in Canada

Abstract To assess the impacts of human activity on fishes and fish habitat, impact assessment tools use single‐ and multi‐species approaches depending on the ecological and socio‐economic objectives. In Canadian aquatic ecosystems, single‐ and multi‐species impact assessments are guided by the Species at Risk Act and Fisheries Act, respectively. Yet, for species protected under the Species at Risk Act, the sparse data often require alternative approaches to risk assessment. The goal of this study was to evaluate whether a database‐derived multi‐species tool – the Habitat Ecosystem Assessment Tool (HEAT) – can be used for single‐species impact assessments. Using an empirical example of proposed drain maintenance in a tributary of Lake St. Clair, the net loss of suitable habitat was evaluated across six conservation targets, ranging from single species, such as the pugnose shiner (Notropis anogenus) and the yellow perch (Perca flavescens), to the entire fish assemblage. Model outcomes were compared across various habitat suitability indices, spatial resolutions, and environmental habitat layers. The net loss of suitable habitat varied widely across conservation targets and was greatest for the rare specialist species (pugnose shiner). Single‐species conservation targets were more sensitive to variation in spatial resolution and uncertainty in model input parameters. The results of this study emphasize that single‐ and multi‐species conservation targets should not be considered equal, especially when species differ in abundance and niche breadth. This study demonstrates the flexibility of HEAT for evaluating potential impacts of human disturbance on fishes and their habitat. Future development of this tool should expand beyond physical habitat, to include other factors relevant to species distribution and survival (e.g. biotic interactions).

Effect of Beaver on Brook Trout Habitat in North Shore, Lake Superior, Streams

AbstractThe Brook Trout Salvelinus fontinalis is a native salmonid that provides a valued and productive sport fishery in northeastern Minnesota. Revival of North American beaver Castor canadensis (hereafter, “beaver”) populations since their near extermination and concern over their impacts on Brook Trout habitat prompted a reexamination of the complex ecological relationship where the two taxa interact. Suitable Brook Trout habitat is characterized by cold, spring‐fed water with silt‐free rocky substrate and abundant cover, all of which beaver may directly or indirectly affect. Data collection occurred on 79 stream sections (200 m each) and 21 beaver ponds spanning the North Shore of Lake Superior during the summer in 2017 and 2018. Habitat suitability index (HSI) models determined the average HSI and quantity of suitable Brook Trout habitat (m2/100 m2) at stream and beaver pond sites, and a bioenergetics model calculated Brook Trout growth availability (m2/100 m2) and mean growth (g/d) at stream sites. Classification regression trees identified significant thresholds at which beaver activity (e.g., number of dams upstream of sampled sites and beaver pond age) influenced the quantity or quality of Brook Trout habitat and growth. No significant variables were identified as affecting Brook Trout habitat or growth rates in stream sites. Alternatively, the quantity and quality of Brook Trout habitat in this region appeared to be influenced by microhabitat variables (depth, velocity, and temperature) that are eminent at individual stream sites. Brook Trout growth was strongly influenced by velocity (m/s) and mean prey concentration (mg dry mass/m3). Results indicated that 12 of the 21 sampled beaver ponds contained suitable Brook Trout habitat, with dissolved oxygen (mg/L) identified as a threshold. This study recommends focusing on individual stream characteristics and beaver pond dissolved oxygen concentrations to achieve desired Brook Trout habitat and aid in the development of management strategies pertaining to these two taxa in Lake Superior's North Shore streams.

Identifying new sites of significance to waterbirds conservation and their habitat modification in the Yellow and Bohai Seas in China

Chinese coastal wetlands in the Yellow and Bohai Seas provide a network of breeding, stopover, and wintering sites that are critical for the survival of many migratory waterbird species. However, land use change, particularly from coastal reclamation, has caused severe population declines of waterirds. Although 19 sites, covering 1.51 million hectares, were recognized as Important Bird Areas (IBAs) prior to 2009, bird surveys since 2009 have indicated additional sites may be important, and should be included in the protection area network. In this study, we compile waterbird distribution data (post-2009) from multiple sources, including citizen science databases, published and gray literatures. Using these data while also adopting internationally recognized criteria, we delineate new sites of significance to waterbird conservation. For these newly identified sites, using remote-sensed data, we develop a habitat suitability index (HSI) to identify any change in the same site between 2000 and 2015. The study results show that of 26 sites meeting criteria for significance to waterbird conservation in Chinese coastal wetlands of the Yellow and Bohai Seas, 9 sites are included within boundaries of existing IBAs, and 17 are new identified sites; Eight threatened waterbird species are recorded in 13 of the newly identified sites; and seven threatened species or species that occurred in internationally significant numbers have not been previously documented in existing IBAs; Decreases in habitat suitability are apparent at 16 of 17 newly identified sites between 2000 and 2015, as are declines in the extent of natural habitat. To curtail future population declines of waterbirds in coastal wetlands of the Yellow and Bohai Seas, prioritized conservation of these newly identified sites is urgently required.

A sequential multi-level framework to improve habitat suitability modelling

ContextHabitat suitability models (HSM) can improve our understanding of a species’ ecology and are valuable tools for informing landscape-scale decisions. We can increase HSM predictive accuracy and derive more realistic conclusions by taking a multi-scale approach. However, this process is often statistically complex and computationally intensive.ObjectivesWe provide an easily implemented, flexible framework for sequential multi-level, multi-scale HSM and compare it to two other commonly-applied approaches: single-level, multi-scale HSM and their post-hoc combinations.MethodsOur framework implements scale optimisation and model tuning at each level in turn, from the highest (population range) to the lowest (e.g. foraging habitat) level, whilst incorporating output habitat suitability indices from a higher level as a predictor. We used MaxEnt and a species of conservation concern in Britain, the lesser horseshoe bat (Rhinolophus hipposideros), to demonstrate and compare multi-scale approaches.ResultsIntegrating models across levels, either by applying our framework, or by multiplying single-level model predictions, improved predictive performance over single-level models. Moreover, differences in the importance and direction of the species-environment associations highlight the potential for false inferences from single-level models or their post-hoc combinations. The single-level summer range model incorrectly identified a positive influence of heathland cover, whereas sequential multi-level models made biological sense and underlined this species’ requirement for extensive broadleaf woodland cover, hedgerows and access to buildings for roosting in rural areas.ConclusionsWe conclude that multi-level HSM appear superior to single-level, multi-scale approaches; models should be sequentially integrated across levels if information on species-environment relationships is of importance.

Modeling the Spatial Distribution of Swordfish (Xiphias gladius) Using Fishery and Remote Sensing Data: Approach and Resolution

Swordfish, Xiphias gladius (Linnaeus, 1758), is a commercially important species that is widely distributed throughout three oceans. This species inhabits oceanic waters with preferred environmental ranges and migrates vertically to the surface layer for feeding. However, the spatial distribution pattern and habitat preferences of swordfish have been rarely studied in the Pacific Ocean due to the wide geographic range of this species. This study examined the spatial distribution and preferred ranges of environmental variables for swordfish using two approaches, generalized additive models and habitat suitability index methods, with different spatio-temporal data resolution scales. Results indicated that sea surface temperature is the most important factor determining swordfish spatial distribution. Habitat spatial pattern and preferred environmental ranges, estimated using various modeling approaches, were robust relative to the spatio-temporal data resolution scales. The models were validated by examining the consistency between predictions and untrained actual observations, which all predicted a high relative density of swordfish in the tropical waters of the central Pacific Ocean, with no obvious seasonal movement. Results from this study, based on fishery and remote sensing data with wide spatial coverage, could benefit the conservation and management of fisheries for highly migratory species such as swordfish and tuna.

Spatio-temporal variations in the potential habitat of a pelagic commercial squid

An integrated habitat suitability index (HSI) model was developed for a pelagic commercial squid Ommastrephes bartramii in the Northwest Pacific Ocean based on three crucial environmental variables: sea surface temperature (SST), chlorophyll-a concentration (Chla) and sea surface height (SSH). The model was established by data from 2006 to 2014 and validated by data in 2015 on the basis of fishing effort and CPUE (catch-per-unit-effort). Results suggested that the HSI model had good capacity to predict habitat suitability for O. bartramii . Squid habitat quality showed significant monthly variation, the ranges of suitable habitats in July and August were much larger than those in September. Besides, the latitudinal location of suitable habitats gradually moved northward from July to September. Further, the spatial extents of potential habitat of O. bartramii across months were strongly regulated by favorable environmental conditions. The variability trends of monthly CPUE and LATG (latitudinal distribution of fishing efforts) were closely associated and consistent with spatio-temporal habitat variations during 2006–2015. Moreover, climate variability strongly affected habitat variations and squid stocks. Relative to the El Niño event in 2015, the La Niña event in 2007 yielded expanded suitable habitat from July to September, consequently, the CPUE was much higher. And the potential high-quality habitats in 2007 mainly located in northern regions except July comparing to 2015, leading to the higher latitudinal distribution of LATG in August and September 2007. Our findings indicated that O. bartramii habitats obviously varied from month to month and were largely affected by environmental changes. • Habitat patterns of Ommastrephes bartramii was examined by habitat modeling approach. • Spatio-temporal variations of O. bartramii habitats showed monthly patterns. • Climatic and environmental variability strongly affected O. bartramii habitats.

Spatial Habitat Shifts of Oceanic Cephalopod (Ommastrephes bartramii) in Oscillating Climate

Short- and long-term climate oscillations impact seascapes, and hence, marine ecosystem structure and dynamics. Here, we explored the spatio-temporal patterns of potential squid habitat in the western and central North Pacific across inter-decadal climate transitions, coincident with periods of persistent warming and cooling. Potential habitat distributions of Ommastrephes bartramii were derived from the outputs of multi-ensemble species distribution models, developed using the most influential environmental factors to squid distribution and occurrence data. Our analyses captured the underlying temporal trends in potential squid habitat in response to environmental changes transpiring at each climatic transition, regulated by phase shifts in Pacific decadal oscillation (PDO) from 1999–2013. The spatial differences in environmental conditions were apparent across transitions and presumably modulate the local changes in suitable squid habitat over time. Specifically, during a cold to warm PDO shift, decreases in the summer potential habitat (mean rate ± standard deviation: −0.04 ± 0.02 habitat suitability index (HSI)/yr) were observed along the southern edge of the subarctic frontal zone (162°E–172°W). Coincidentally, this area also exhibits a warming trend (mean temporal trend: 0.06 ± 0.21 °C/yr), accompanied with the prevalence of cold-core mesoscale eddies, west of the dateline (mean temporal trend in sea surface height: −0.19 ± 1.05 cm/yr). These conditions potentially generate less favorable foraging habitat for squid. However, a warm-to-cold PDO transition underpins a northward shift of suitable habitat and an eastward shift of regions exhibiting the highest rate of potential squid habitat loss (170–160°W; mean temporal trend: −0.05 ± 0.03 HSI/yr). Nonetheless, the emergence of the areas with increasingly suitable habitat regardless of climate transitions suggests the ecological importance of these regions as potential squid habitat hotspots and climatic refugia.

Hit or miss? Evaluating the effectiveness of Natura 2000 for conservation of forest bird habitat in Sweden

Biodiversity conservation often requires a landscape perspective. When establishing the Natura 2000 (N2k) network, the effectiveness of the sites and the influence of the surrounding landscapes for species of interest was often disregarded. We analyzed the effectiveness of N2k sites in Sweden for three forest bird species of conservation interest in the European boreal landscapes: lesser spotted woodpecker (LSW), Siberian jay (SJ) and hazel grouse (HG). Our objectives were to: 1) quantify effective suitable habitat area in N2k sites with and without consideration of the adjoining landscapes; 2) examine effective habitat area within N2k sites along the north-south vegetation gradient 3) analyze functionality of N2k sites and assess how forests outside the sites affect habitat suitability inside N2k. GIS-based habitat suitability index models were applied to calculate the amount of effective habitat within and outside N2k sites. N2k sites contributed with 10% (HG), 13% (SJ) and 51% (LSW) suitable habitat identified in Sweden. Functionality of forest environments as habitat was higher inside N2k sites for LSW within all vegetation zones, and for SJ in the Alpine and Middle Boreal zones; for HG habitat outside the sites was more functional in all zones accept Alpine and Middle Boreal. The majority of N2k sites were of quite small size (<500 ha) and the size influenced their functionality for LSW and HG, with larger N2k sites being more functional. For SJ, however, average functionality of N2k sites was not influenced by their size. The largest average habitat increase linked to considering the contribution of areas outside N2k sites for their functionality as habitat was for the N2k sites of smaller size (1-500 ha). Therefore, the presence and quality of forests outside of N2k sites are of a greater importance for smaller sites, and as such these should be carefully managed. To improve conservation efficiency of the N2k sites in Sweden, we call for incorporating them into the development and implementation of the regional Green Infrastructure plans.