Localized invasion of the North American Harris mud crab, Rhithropanopeus harrisii, in the Panama Canal: implications for eradication and spread

Abstract

As the rate of biological invasions continues to increase, a growing number of aquatic introduced species are becoming globally widespread. Despite this ubiquitous phenomenon, rarely do we discover aquatic invaders early enough to allow the possibility of eradication. Recently, the North American Harris mud crab (Rhithropanopeus harrisii) was found in the waters adjacent to the Panama Canal and herein we provide an assessment of the crab’s distribution in Panama to evaluate the possibility of eradication. Using salinity tolerance experiments, we also evaluate the potential for further spread of this crab within the Canal. Our results suggest that populations of R. harrisii are currently limited to two manmade lagoons which are adjacent to the Panama Canal. Our experiments suggest that both juvenile and adult R. harrisii can survive in salinities found outside its current range in Panama. Although it is difficult to predict the potential for future spread and impacts in Panama, current management strategies could reduce the probability for spread locally as well as elsewhere in the world given the intensity of shipping in this region. The current containment of this invader suggests that a localized eradication may be possible.

Appendix

Measurements of surface salinity (parts per thousand) at different sites along the Panama Canal (modified from Cohen 2006)

Date	Pacific Approach	SL	NL	MF Spillway	MF Lower Locks	MF Upper Locks	MF Lake	Pedro Miguel Locks	Gatun Lake	Gatun Upper Locks	Gatun Lower Locks	Gatun TLL	Gatun Spillway	Atlantic Approach	Ref.
Jun 1935										0	10–16			18–20	1
<1939	16–20						0.1–3.0		≤0.02					18–20	1
≤1968	30a				26a		1.0a	0.0a	0.0a		24a			28.5a	2
Feb 1969								0.0–0.4							3
Jan 1972						20b									4
Apr 1972	27					1–3a	0a	0a	0a	0.1a	5–11a			17a	5
Nov 1972	23a				14–15	3a	0–1a	0a	0a	0.2–0.3a	6–8a			10–17a	5
Mar 1974									0.2	0.02–0.8					6
Jun 2007		4c	0c												7
Jul 2007		3c	0c												7
Aug 2007		3.3	0.4–0.6	0.1–3.4d			0.3–0.4								7
Sep 2007	19.3–20.3						0.2–0.5								7
Oct 2007		2.8–2.9	0.4	0.9–7.6d											7
Nov 2007		2.3	0.4				0.2–0.4		0.1						7
Dec 2007		2.1–2.2	0.4				0.1–0.5								7
Jan 2008		2.1	0.4				0.4e		0.1			0.2	0.1–0.2d	14.4–24.4	7
Feb 2008	14.1–20.0	2.5–2.6	0.5				0.5e					0.2	1.5–10.5	23.3–24.5	7
Mar 2008		3.1–3.6	0.6				0.6–0.7e								7
Apr 2008		4.1–4.3	0.6				0.6e								7

1. Abbreviations: MF = Miraflores, SL = Southern Lagoon, NL = Northern Lagoon
2. ^aValues estimated by Cohen (2006)
3. ^bIn sump areas after dewatering
4. ^cMeasured with a refractometer
5. ^dAt low tide
6. ^eAt the culvert connection with the NL
7. References: (1) Hildebrand 1939, (2) Menzies 1968, (3) Abele 1972, (4) Dawson 1973, (5) Jones and Dawson 1973, (6) Jones and Rützler 1975, (7) this study