RCrab: An R Analytics Tool to Visualize and Analyze the Movement of Horseshoe Crabs in Long Island Sound

Mark-recapture programs are important for studying the ecology and population dynamics of wildlife. An R shiny analytics tool was developed to track the movement of horseshoe crabs in Long Island Sound based on tag and resight data. The crabs were tagged and recaptured by volunteers of Project Limulus, a community-based research program. The dataset contains tag and recapture location information for 14,065 horseshoe crabs over 18 years. The dataset was initially cleaned by removing records with missing, duplicate or incorrect data. A new data structure was developed to save the data and simplify processing: Three dimensions were used, one for the original horseshoe crab tag data, the second for the recapture data, and the third for the mating behavior data recorded both when originally tagged and when found during the recaptures. The R tools enables scientists and the general public to easily produce charts and movement maps based on the dataset. To study horseshoe crab movement, the Long Island Sound area was divided into five major tagging activity areas. Our results show that horseshoe crabs can cross the Sound (from CT to NY and back) and an interesting trend of movement towards the northern and eastern parts of Long Island Sound which correlates with less pollution and human disturbance

Conceptualizing the construct of ocean identity

The construct of ocean identity provides a valuable lens that can unpack the multiple dimensions of human connections with ocean spaces, and crucially places importance on the integration of cognitive, affective, and behavioral components. The construct of ocean identity is applicable in academic and professional contexts, and is largely unexplored from both qualitative and quantitative research perspectives. This comment article presents a revised definition of ocean identity and posits a useful conceptual framework based on a robust analysis of literature to unveil the multiple dimensions that may explain an individuals’ ocean identity. Here we identify a series of attributes that could be considered possible explanatory attributes of the emerging concept of ocean identity. Future research will statistically test the concepts presented here to validate a scale for measuring ocean identity. This piece contributes to the ongoing ocean literacy discourse and deepens our understanding of the multiple conceptual dimensions of ocean identity

A Random Forest Regression Model for Predicting the Movement of Horseshoe Crabs in Long Island Sound

Developing models to predict animal movement patterns is an important area of study in ecology and wildlife management. Project Limulus, a community research program, has been tracking the movement of tagged American horseshoe crabs (Limulus polyphemus) in Long Island Sound since 1998. During the spawning season, horseshoe crabs are captured by hand, tagged and then released. Recaptured horseshoe crabs give valuable information about their behavior and movement patterns. In this paper, we tested various models to find the best predictor for the movement of horseshoe crabs based on the observed movement activity in previous years. We experimented with three different models: Linear Regression, Decision Tree, and Random Forest Regression models. We used the data for 2018 as our test set and the data of all previous 19 years as our training set (19,219 records). The Random Forest Regression model proved to be the best predictive model and resulted in the smallest RMSE and MAE, as well as the smallest maximum error in prediction. The predicted horseshoe crab locations can be targeted in the next season for recapturing tagged horseshoe crabs. It also concentrates the scientists’ effort and time to find the maximum number of horseshoe crabs

Movement Patterns and Population Genetics of the American Horseshoe Crab in Relation to Long Island Sound Conservation Strategies

The Connecticut Department of Environmental Protection (CTDEP) established three no-harvest zones for the horseshoe crab (Limulus polyphemus) population as part of a conservation plan for the species. Data from a long-term mark/recapture study of horseshoe crabs in conjunction with a microsatellite-based genetic survey of the population were analyzed to determine if this plan was appropriate to conserve genetic diversity and broaden our knowledge of movement patterns of Limulus in Long Island Sound (LIS). To date, ~53,000 crabs have been tagged over a 10 year period through the Project Limulus program with an annual average recapture rate of 12 to 15%. In addition to the ongoing tagging study, 187 horseshoe crabs collected from 5 distinct sites spanning the geographic extent of Long Island Sound (Rye and Mt. Sinai, NY; Milford, New Haven, and Groton, CT) were genotyped for 11 microsatellite loci to determine the overall genetic health of the LIS population and determine if regional genetic differentiation was sufficient to identify sub-populations within this region. The genetic data indicates that the LIS Limulus population is genetically homogenous with no signs of inbreeding and substantially similar to other Mid-Atlantic populations. Data from the mark-recapture study indicate significant migration east and west along the north shore of LIS relative to the original tag site and in addition cross LIS migrations have also been observed. Therefore, the locations of the established no-harvest zones are appropriate to conserve genetic diversity. However, based on their tri-state migration patterns, a multi-state management strategy is needed for the LIS horseshoe crab population

The Power of Citizen Science: 20 Years of Horseshoe Crab Community Research Merging Conservation, Education, and Management

Long-term observations of the distribution, mating behavior, and movement patterns of horseshoe crabs are important for understanding their ecology. Population genetic analyses are useful to define ecological management units. Combined, this information informs the management of the species. Citizen science, the active public involvement in scientific research, can result in the production of “big data” both spatially and temporally especially when volunteers are involved with tagging (mark/recapture) studies and spawning counts. In this study, involving Limulus polyphemus, citizen scientists placed over 76% of our 95,567 tags put out on horseshoe crabs over 20 years in Long Island Sound (LIS) and reported nearly 85% of our recaptures. Of the 15,655 marked and recaptured horseshoe crabs, 18% had moved more than 10 km and 547 individuals crossed the Sound from Connecticut (CT) shores to the northshore of Long Island, New York (NY). Our genetic analysis of 11 microsatellite loci from 186 individuals from five areas across the Sound found no population substructure and no inbreeding depression. This supported the results of the tagging study. Thus, the horseshoe crab population of the New York region is panmictic. It is known from observations in Delaware Bay during May and June that horseshoe crabs are a dominant species (spawning index ~1 female/m2) and their egg-laying activity directly increases biodiversity and biomass on beaches and in estuaries where they are abundant. When horseshoe crab populations decline, as observed in LIS, so do the number of species and the populations of dependent predator species that feed on their eggs. The spawning index is low 0.009–0.036 female/m2 and generally has been declining over the past 10 years in LIS. The trend from over 15 years of tagging shows 20–30% of the females come up to the beach without a mate. In LIS, a shared resource of Connecticut and New York, horseshoe crab populations continue to be overharvested and continue to decline, which has a negative impact on biodiversity. How these results relate to the three Asian horseshoe crab species will be discussed. The horseshoe crab population in the New York region is breeding well below its intrinsic rate of growth. A moratorium on the harvest of horseshoe crabs is needed; investment in coastal habitat restoration and establishment of marine protected areas in LIS are also required for recovery of the population