Spatial and temporal distribution of horseshoe crab (Limulus polyphemus) spawning in Delaware Bay: Implications for monitoring

Conservation status of the American horseshoe crab, (Limulus polyphemus): a regional assessment

“…Daily spawning activity is associated with high tides, which they detect through changes in water depth (Chabot et al 2008;Chabot and Watson 2010;Chabot et al 2011). Some observations suggest that horseshoe crabs prefer to spawn around the time of the new and full moon high tides, which are the highest tides of the month (Rudloe 1980;Brockmann 2003b;Barlow et al 1986;Brockmann and Johnson 2011;Smith et al 2002b, Chabot et al 2008Watson and Chabot 2010). However, other studies have reported that the association between spawning activity and the lunar period is not strong or only slightly higher than expected by chance alone Cheng et al 2016) and that spawning occurs at a similar intensity during all daytime high tides regardless of lunar phase (James-Pirri et al 2005;Leschen et al 2006).…”

“…Unattached males return to the beach more frequently than females, creating male-biased OSR and male-male competition for mates (Rudloe 1980;Brockmann 1990;Smith et al 2002aSmith et al , 2010Brockmann and Smith 2009;Brockmann and Johnson 2011). The mean OSR in unharvested populations is generally 1.5-2.4 males to females (Rudloe 1980;Wenner and Thompson 2000;Schaller 2002;Brockmann and Johnson 2011), but in populations with female-biased harvest the sex ratio is elevated, i.e., 3 to 8 males/female (Smith et al 2002b(Smith et al , 2009aCarmichael et al 2003;James-Pirri et al 2005;Kreamer and Michels 2009). Mean OSR during the 2012-2013 spawning season in Chuburná, Yucatán, was 1.1 males to females (unpublished data, J. Gutiérrez and J. Zaldívar-Rae, Anáhuac Mayab University).…”

“…All the surveys encounter horseshoe crabs regularly and the respective state agencies rely on them to comply with ASMFC monitoring requirements. However, only the spawning surveys and one benthic trawl in the Delaware Bay area were specially designed to monitor horseshoe crabs (Smith et al 2002b;Hata and Berkson 2004). The primary data were individual counts of horseshoe crabs within sampling units; the demographic (age-class, sex) and temporal and spatial resolution of each dataset are described in Sweka et al (2013: Appendix B) and summarized in Table 3.…”

Abundance and population structure of the Atlantic horseshoe crab Limulus polyphemus in Pleasant Bay, Cape Cod

“…Berkson unpubl.). Other studies conducted on individual beaches sampled only adult spawning crabs (Baptist et al 1957, Sokoloff 1978, Rudloe 1980, Shuster & Botton 1985, Widener & Barlow 1999, Smith et al 2002, which make up only a portion of the population. More comprehensive whole-estuary and wholepopulation studies are needed in the shallow water, where horseshoe crabs are abundant.…”

The Horseshoe Crab, Limulus polyphemus: 200 Million Years of Existence, 100 Years of Study

“…These include redesigned spawning surveys using a sound statistical design that were first implemented in 1999 (Smith et al, 2002). With only 2 years of data available from this survey, it is not possible to draw meaningful conclusions about horseshoe crab population status.…”