Distribution of juvenile American horseshoe crabs Limulus polyphemus in the Great Bay Estuary, New Hampshire, USA

Abstract

In order to effectively manage a fishery, it is important to know the essential habitats used by all life history stages of the species being managed. However, this is often a challenge for animals such as the American horseshoe crab Limulus polyphemus, whose juvenile stages are difficult to find and quantify. Visual surveys and suction sampling have been used in previous studies, but in the Great Bay Estuary, New Hampshire, they are less effective, and so little is known about the habitats occupied by juvenile horseshoe crabs in this area. To fill this knowledge gap, we used SCUBA-dive surveys to locate juvenile horseshoe crabs. We found them on subtidal and some intertidal mudflats in the upper regions of the estuary, both adjacent to, and at some distance from, known spawning beaches. However we did not find them in either intertidal or subtidal areas adjacent to spawning beaches just 1-2 km closer to the coast. These data should be useful for future conservation efforts designed to protect essential horseshoe crab habitats in the Great Bay and other similar estuaries.

Contrasting Trophic Niche and Resource Use Dynamics Across Multiple American Horseshoe Crab (Limulus polyphemus) Populations and Age Groups

“…δ 34 S values measured in the current study further corroborate differences in movement, as adults appeared to have more enriched δ 34 S values compared to juveniles, indicating that adults migrate and access prey (e.g., bivalves) or SOM offshore that is more enriched in δ 34 S compared to the δ 34 S signatures of some estuarine organic matter sources (Rubenstein and Hobson 2004). Depleted δ 34 S values within juveniles could also be attributed to their tendencies to occupy mud-based habitats (Cheng et al 2021) that have higher sulfide concentrations from bacterial sulfate reduction (Brüchert and Pratt 1996). When considering these ontogenetic differences in space use, it appears that adults and juveniles exhibit moderate resource partitioning across space and time, which may be beneficial to reduce intraspecific foraging competition and may optimize fitness (Svanbäck and Bolnick 2007).…”

“…The lack of seasonal changes in resource use is not surprising for this life history stage given their localized movement patterns among estuarine habitats and low emigration from coastal estuaries (Bopp et al 2021). Juveniles have been observed to have a strong preference for subtidal mud substrates (Cheng et al 2021), which are richer in organic matter compared to coarser sediments (Serrano et al 2016), and may explain their assimilatory preferences for SOM. However, the constituents and quality of SOM often vary seasonally in temperate estuaries (Lesen 2006) and should be examined to determine its bioenergetic implications on horseshoe crab metabolism.…”

Assessment of recovery potential for the American horseshoe crab (Limulus polyphemus): An application of the IUCN green status process

“…If climate change results in more frequent storms, they could disrupt migrations, spawning phenology and egg survival. In addition, flooding causes freshwater intrusion, which could affect nursery and juvenile habitats in nearshore and intertidal environments proximate to spawning habitat (Bopp et al, 2021; Cheng, Chabot & Watson, 2021; Colon et al, 2022). In some spatial units, shifts in the spatial or temporal patterns of spawning could disrupt interspecific relationships and interfere with the populations achieving ecological functionality, such as a possible mismatch between shorebird migrations and horseshoe crab spawning in Delaware Bay (Smith et al, 2011; Tucker et al, 2019).…”

The use of alternative spawning habitats by the American horseshoe crab,Limulus polyphemus

“…1988; Walls et al . 2002; Cheng et al . 2021), and studies have indicated that the area around the beach high tide line provides the best conditions for embryonic development (Penn and Brockmann 1994; Vasquez et al .…”

“…Horseshoe crabs are traditionally thought to spawn primarily on sandy beaches (e.g., Botton et al 1988;Walls et al 2002;Cheng et al 2021), and studies have indicated that the area around the beach high tide line provides the best conditions for embryonic development (Penn and Brockmann 1994;Vasquez et al 2015a,b). Due in part to the belief that horseshoe crabs spawn primarily on sandy beaches, horseshoe crab adult spawning and egg surveys have been conducted almost entirely in beach habitats (e.g., Smith et al 2002;Smith and Robinson 2015).…”