Saved by the shell: Oyster reefs can shield juvenile blue crabs Callinectes sapidus

Ks Longmire,Rd Seitz,A Smith,Rn Lipcius

doi:10.3354/meps13781

Abstract

Juvenile blue crabs Callinectes sapidus use seagrass and other structured habitats as refuges from predation. Oyster reef habitats provide structural complexity that may offer refuge, but the value of these habitats for juvenile blue crabs has not been examined. We quantified survival of juvenile C. sapidus in structured oyster reef habitat versus unstructured soft-bottom habitat. In a field tethering experiment in the York River, lower Chesapeake Bay (USA), juvenile C. sapidus (10-50 mm carapace width [CW]) were tethered in sand (n = 40) or oyster reef (n = 39) habitats at subtidal sites 1-2 m deep. An underwater camera system was used to record predation activity during 24 h trials. Juvenile crab survival was significantly higher on the oyster reef habitat (53.8%) than on bare sand (15.0%), and tended to increase with crab CW in both habitats. The main successful predators on juvenile blue crabs were northern pufferfish Sphoeroides maculatus in the oyster reef habitat and adult blue crabs in the sand habitat. The high survival rate of juvenile C. sapidus in oyster reef habitats suggests that oyster reefs include physical habitat complexity that may offer refuge from predators. Restored and natural oyster reefs could provide an alternative nursery habitat for juvenile blue crabs, expanding the ecosystem services provided by restored oyster reefs.

Highlights

Structure can reduce the ability of a predator to find prey (Grabowski 2004), which may be key in reducing predator−prey and cannibalistic interactions of adult and juvenile blue crabs (Moksnes et al 1997)
Blue crab survival is enhanced in structured seagrass
This study was conducted in the York River at a subtidal (1−2 m water depth) location near the Virginia Institute of Marine Science (VIMS) in Gloucester Point, VA, from late July through early October 2017

Summary

Introduction

Complex habitats can serve as nursery grounds for many invertebrates, including blue crabs Callinectes sapidus. Structured nursery habitats for blue crabs include seagrass beds (Heck & Thoman 1984, Heck et al 2003, Lipcius et al 2005, Seitz et al 2005, Ralph et al 2013), non-native algae (Johnston & Lipcius 2012), salt marshes (Minello et al 2003), and coarse woody debris (Everett & Ruiz 1993). Structure can reduce the ability of a predator to find prey (Grabowski 2004), which may be key in reducing predator−prey and cannibalistic interactions of adult and juvenile blue crabs (Moksnes et al 1997). Blue crab survival is enhanced in structured seagrass.

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