Horseshoe Crab Spawning Survey

data.delaware.gov | Last Updated 5 Jun 2019

Survey data from 1999-2018 which denotes peak spawning occurrences by day and lunar period, proportion of spawning in May (coinciding with shorebird stopovers), average water temperature, index values for female and male crabs per square meter by beach and baywide, the annual sex ratio, and index of abundance per beach.

Tags: horeshoe crab, spawning, beach, survey, volunteer, dnrec

This dataset has the following 34 columns:

Column NameAPI Column NameData TypeDescriptionSample Values
YearyearnumberYear of survey
DE % Female Spawning in Mayde_female_spawning_in_maynumberProportion of females recorded during May of a given survey year on Delaware beaches
NJ % Female Spawning in Maynj_female_spawning_in_maynumberProportion of females recorded during May of a given survey year on New Jersey Beaches
Avg. Daily Water Temp. in May (°C)avg_daily_water_temp_in_may_cnumberAverage of daily water temperatures recorded at the National Ocean Service station at Lewes, DE (Station Identification Number 8557380) during the month of May in °Celsius
Baywide Spawning Activity Lunar Period 1baywide_spawning_activity_lunar_period_1numberThe mean of the total number of female crabs per total area available for the spawning survey on all surveyed beaches. The first moon phase (new or full) in May around which surveying begins - 2 days before, day of, 2 days after.
Baywide Spawning ActivityLunar Period 2baywide_spawning_activitylunar_period_2numberThe mean of the total number of female crabs per total area available for the spawning survey on all surveyed beaches. The second moon phase (new or full) in May around which surveying occurs - 2 days before, day of, 2 days after.
Baywide Spawning ActivityLunar Period 3baywide_spawning_activitylunar_period_3numberThe mean of the total number of female crabs per total area available for the spawning survey on all surveyed beaches. The first moon phase (new or full) in June around which surveying occurs - 2 days before, day of, 2 days after.
Baywide Spawning ActivityLunar Period 4baywide_spawning_activitylunar_period_4numberThe mean of the total number of female crabs per total area available for the spawning survey on all surveyed beaches. The second moon phase (new or full) in June around which surveying occurs - 2 days before, day of, 2 days after (typically the last period of surveying).
Number of Males per FemalenumbermalesperfemalenumberThe number of males observed in a given spawning season per female observed during that same season.
Total Beaches Surveyedtotal_beaches_surveyednumberNumber of beaches on which the standardized form of the spawning survey was conducted baywide
Baywide Male Spawning Activitybaywide_male_spawning_activitynumberThe mean of the total number of male crabs per total area available for the spawning survey on all surveyed beaches.
Baywide Male 90% CI Lower Limitbaywide_male_90_ci_lower_limitnumber90% Confidence Interval - Lower limit of values where there exists a 90% probability of male horseshoe crab spawning activity
Baywide Male 90% CI Upper Limitbaywide_male_90_ci_upper_limitnumber90% Confidence Interval - Upper limit of values where there exists a 90% probability of male horseshoe crab spawning activity
Baywide Male SDbaywide_male_sdnumberStandard Deviation - Statistical variation of Index of Spawning Activity (ISA) values for males
Baywide Male CVbaywide_male_cvnumberCoefficient of variation - Unitless description of the amount of variation relative to the mean Index of Spawning Activity (ISA), expressed as a percentage for males
Baywide Female Spawning Activitybaywide_female_spawning_activitynumberIndex of female horseshoe crab spawning activity - mean number of female crabs per square meter per night for Delaware and New Jersey beaches
Baywide Female 90% CI Lower Limitbaywide_female_90_ci_lower_limitnumber90% Confidence Interval - Lower limit of values where there exists a 90% probability of female horseshoe crab spawning activity
Baywide Female 90% CI Upper Limitbaywide_female_90_ci_upper_limitnumber90% Confidence Interval - Upper limit of values where there exists a 90% probability of female horseshoe crab spawning activity
Baywide Female SDbaywide_female_sdnumberStandard Deviation - Statistical variation of Index of Spawning Activity (ISA) values for females
Baywide Female CVbaywide_female_cvnumberCoefficient of variation - Unitless description of the amount of variation relative to the mean Index of Spawning Activity (ISA), expressed as a percentage for females
DE Beaches Surveyedde_beaches_surveyednumberNumber of beaches on which the standardized form of the spawning survey was conducted in Delaware
DE Male Spawning Activityde_male_spawning_activitynumberThe mean of the total number of male crabs per total area available for the spawning survey on all DE surveyed beaches
DE Male 90% CI Lower Limitde_male_90_ci_lower_limitnumber90% Confidence Interval - Lower limit of values where there exists a 90% probability of male horseshoe crab spawning activity in Delaware
DE Male 90% CI Upper Limitde_male_90_ci_upper_limitnumber90% Confidence Interval - Upper limit of values where there exists a 90% probability of female horseshoe crab spawning activity in Delaware
DE Female Spawning Activityde_female_spawning_activitynumberThe mean of the total number of female crabs per total area available for the spawning survey on all DE surveyed beaches
DE Female 90% CI Lower Limitde_female_90_ci_lower_limitnumber90% Confidence Interval - Lower limit of values where there exists a 90% probability of female horseshoe crab spawning activity in Delaware
DE Female 90% CI Upper Limitde_female_90_ci_upper_limitnumber90% Confidence Interval - Upper limit of values where there exists a 90% probability of female horseshoe crab spawning activity in Delaware
NJ Beaches Surveyednj_beaches_surveyednumberNumber of beaches on which the standardized form of the spawning survey was conducted in New Jersey
NJ Male Spawning Activitynj_male_spawning_activitynumberThe mean of the total number of male crabs per total area available for the spawning survey on all NJ surveyed beaches
NJ Male 90% CI Lower Limitnj_male_90_ci_lower_limitnumber90% Confidence Interval - Lower limit of values where there exists a 90% probability of male horseshoe crab spawning activity in New Jersey
NJ Male 90% CI Upper Limitnj_male_90_ci_upper_limitnumber90% Confidence Interval - Upper limit of values where there exists a 90% probability of male horseshoe crab spawning activity in New Jersey
NJ Female Spawning Activitynj_female_spawning_activitynumberThe mean of the total number of female crabs per total area available for the spawning survey on all NJ surveyed beaches
NJ Female 90% CI Lower Limitnj_female_90_ci_lower_limitnumber90% Confidence Interval - Lower limit of values where there exists a 90% probability of female horseshoe crab spawning activity in New Jersey
NJ Female 90% CI Upper Limitnj_female_90_ci_upper_limitnumber90% Confidence Interval - Upper limit of values where there exists a 90% probability of female horseshoe crab spawning activity in New Jersey