Assessing Intertidal Populations of the Invasive European Green Crab

Summary

Understanding spatiotemporal patterns in green crab population dynamics is essential for predicting and managing the ecological and economic impacts of this harmful invasive species. This protocol was developed in an effort to create a standardized method for assessing green crab populations in the rocky intertidal zone of the Northwest Atlantic.

Abstract

Invasive species have caused major disruptions to ecosystems worldwide. The European green crab invaded North America in the 1800s and is considered one of the world’s 100 worst invaders by the IUCN. Observations of spatiotemporal green crab population dynamics are essential for predicting and managing the ecological and economic impacts of this harmful invasive species. This protocol was developed in an effort to create a standardized method for assessing green crab population dynamics in the rocky intertidal zone of New England and Atlantic Canada. The protocol was designed to be accessible to multiple users including researchers, educators, students, and citizen scientists. Although it was designed for surveying crab populations, this protocol is easy to adapt and could be used for any number of intertidal species. The resulting data collected using this protocol has a wide range of uses, including to inform ecological research, conservation efforts, mitigation strategies, and fishery development, as well as for educational outreach purposes.

Introduction

Biological invasions can potentially disrupt species interactions and ecological processes, and may have far reaching ecological^1,2,3 and economic consequences⁴. The ability to successfully predict, mitigate, and adapt to invasions strongly depends on characterizing spatiotemporal population dynamics⁵. While a range of tools exist (e.g., population genetics, stable isotopes) and are emerging (e.g., eDNA) for tracking invasive species, traditional in situ monitoring techniques continue to be widely utilized for assessing invasive....

Protocol

1. Timing of survey work

1. Conduct surveys between May-November, during the height of productivity in the intertidal zone.
2. Schedule surveys around negative or zero tides (generally new and full moon cycles) to allow for adequate time in the low intertidal zone (i.e., at least 2 hours).

2. Pre-survey preparation

1. Locate and print all field guides and data collection sheets (see Appendices) prior to conducting the survey if that is the preferred method. If u.......

Discussion

This protocol describes a survey method for assessing spatial and temporal trends of crab populations in the rocky intertidal zone that is accessible to multiple users including researchers, educators, students, and citizen scientists. The benefits of this protocol include the following: it does not require specialized or expensive equipment, the methodology is approachable for a wide range of skill levels (e.g., 3^rd and 4^th grade students have successfully used it), and it can easily be adapted to .......

Materials

Name	Company	Catalog Number	Comments
1 m2 PVC quadrat (1/2" PVC)	Any hardware/home improvement store		PVC can be sourced at any hardware/home improvement store and cut into 1m lengths to form quadrat (4 1/2" PVC elbows will also be needed to connect 1 m lengths into square)
1/2" rebar	Home depot	5152	*optional (for marking low intertidal area)
40 m Fiberglass Transect Tape	Grainger	3LJX1
5 gal bucket	Home depot	05GLHD2
Ade Advanced Optics Salinity Refractometer	Amazon		*optional
Clip board	Any office supply store or Amazon
Uei Waterproof Digital Thermometer	Amazon		*optional
Vernier calipers	Bel-Art		Many companies make calipers, however our preferred brand is Bel-Art which can be sourced on Amazon