Field surveys to determine the extent of distribution and relative abundance of Charybdis japonica in the Whangarei region

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1 Taihoro Nukurangi Field surveys to determine the extent of distribution and relative abundance of Charybdis japonica in the Whangarei region Authors Graeme J. Inglis, Nick Gust, Graeme Mackay, Rob Tasker Final Research Report for Ministry of Fisheries Research Project ZBS2001/01 Objective 3 National Institute of Water and Atmospheric Research May 2004

2 " I Final Research Report Report Title: Authors: Field surveys to determine the extent of distribution and relative abundance of Charybdis japonica in the Whangarei region Graeme 1. fuglis, Nick Gust, Graeme Mackay, Rob Tasker 1. Date: II-May Contractor: National fustitute of Water and Atmospheric Research Ltd 3. Project Title: 4. Project Code: Surveillance for exotic marine organisms in New Zealand ZBS2001/01 Objective 3 5. Project Leader: Graeme fuglis 6. Duration of Project: Start date: Completion date: 48 days 13/04/ Background The non-indigenous portunid crab, Charybdis japonica, was first reported in New Zealand from Waitemata Harbour in 2000 (Webber 2001, Smith et al. 2003). C. japonica is likely to have been introduced to New Zealand by ships arriving from its native range in coastal regions of China, Japan, Korea, Taiwan and Malaysia and the western Pacific. Delimitation surveys of the introduced population were undertaken in April and October 2002 throughout Waitemata Harbour and the Hauraki Gulf. At that time C. japonica was widely distributed and abundant throughout Waitemata Harbour, but the population did not appear to have spread further than about 30 km from the harbour entrance (Gust et al. 2002). The northern-most specimens were trapped in Wieti Estuary, approximately 25 km north of Waitemata Harbour, whilst the southern-most record was from Tamaki estuary, ~ 10 km south of the harbour entrance. fu September 2003, a single, mature female C. japonica was captured adjacent to Port Whangarei in Whangarei Harbour, approximately 140 km north of Waitemata Harbour (fuglis and Gust 2003). This record represented a significant range extension from the Auckland population. The crab was captured during the Winter 1 targeted 1

3 surveillance survey of Whangarei Harbour. More than 180 baited traps were set during the survey, at 69 locations throughout Whangarei Harbour, but no further specimens were,captured. Shortly after the survey, NIW A received two anecdotal reports of "unusual" crabs near Whangarei; one from the vicinity of Snake Bank, an important cockle harvesting area in Whangarei Harbour, and another from the Ruakaka Estuary, south of Whangarei Harbour. The report from Ruakaka described a large, blue or purple-coloured crab present in shallow water near the Ruakaka camp ground. In each case, the reports were made by members of the public, but no specimens were retained to confirm identification. In March 2004, NIW A again trapped more than 50 locations in Whangarei Harbour as part of the Summer 2 targeted surveillance and did not capture any additional specimens of C. japonica (Gust et al. 2004). The Ministry of Fisheries contracted NIW A to extend the trapping surveys for C. japonica to four additional estuaries (Ngunguru, Pataua, Ruakaka and Mangawhai) north and south of Whangarei (Fig. 1) to determine the extent of distribution and relative abundance of Charybdis in the Whangarei region. i' 8. Objective: To determine the extent of distribution and relative abundance of Charybdis in the Whangarei region by trapping for Charybdis in four other estuaries north and south of Whangarei. 9. Methods: ~ ~.!,,",,', '.,;. ~'..,, ~/. :"'1" U ~,. ':'.r,'~,., ',' The four estuaries were sampled between 20 th and 28 th April 2004 (Table 1). Ten to 15 locations, distributed throughout the navigable area of each estuary (i.e. > 0.5 m water depth), were trapped for Charybdis (Table 1, Fig.s 2-5). Sampling was done using collapsible box crab traps (62 cm x 42 cm x 20 cm) baited with 1-2 pilchards each. At each location, three baited traps were clipped to a 30 m trap line at approximately 5 m intervals. The lines were weighted with a single anchor and marked by a floating buoy at the water surface. The GPS location of the trap line and the water depth were recorded at the time of each deployment. All traps were left overnight before being retrieved. Brachyuran crabs recovered from the traps were identified in the field and reference specimens kept for validation. Table 1. Summary of trapping effort in each estuary. The numbers of locations sampled and total numbers of traps (brackets) deployed in each estuary are indicated., ; Estuary Date surveyed No. of locations trapped (No. of traps) Ngunguru April (45) Pataua April (45) Ruakaka April (30) Mangawhai April (45) The field teams also undertook visual searches of the intertidal shoreline in each estuary to look for cast exuviae along the driftline. Contact was also made with commercial crab fishermen from the Whangarei district to determine if they had rec~rded C.japonica in any of their recent catches. 2

4 10. Results: No specimens of C. japonica were captured during the survey of the four estuaries. The most abund~t brachyuran crabs recorded from the traps were the native portunid, Ovalipes catharus (White, 1843) and the hairy handed crab, Hemigrapsus crenulatus (H. Milne Edwards, 1837) Ovalipes catharus was most abundant in Mangiwhai estuary (Fig.s 6 and 13). H. crenulatus was particularly abundant in Ruakaka estuary, where it was caught at all trapped locations at an average of 12 (±4) crabs per trap line (Fig.s 6 and 12). In contrast, very few H. crenulatus were captured in the three other estuaries «1 crab per trap line) (Fig.s 6,8,10 and 14)., '.' Three commercial crab fishers in the Whangarei region were interviewed by NIW A to determine if Charybdis had appeared in their catch. Bill Richardson is based in Parua Bay and fishes within Bream Bay and Whangarei Harbour; Phil Tanner is based at Ruakaka and also fishes in the Whangarei district; and John Charles fishes out of Mangawhai Heads. None of the fishermen had seen C. japonica in that region, but all three agreed to notify MFish and NIW A of any unusual specimens that they trapped. Interestingly, John Charles fished Waitemata Harbour and surrounding areas of the inner Hauraki Gulf during the 1990's and claimed to be catching C. japonica for at least 6 years prior to the first official record in 2000, when specimens were lodged with Te Papa for formal identification. 11. Conclusions: t;, ",.,~~ We found no evidence from field surveys carried out in Whangarei Harbour (Gust et al. 2004), Ngunguru, Pataua, Ruakaka and Mangawhai estuaries that the introduced portunid crab, C. japonica, has established a permanent population in the Whangarei region. This finding was reinforced by the observations of commercial crab fishermen in the region, none of whom had recovered C. japonica from their catches. It appears that the capture of a single specimen in September 2003 may have been an isolated event, rather that an expansion of the current known range. 12. Literature Cited: Gust, N.; Inglis, G.J.; Smith, M Delimitation survey for the invasive swimming crab Charybdis japonica in the Auckland region. Final Research Report for Ministry of Fisheries Research Projects ZBS2001l01 Objective 1 & ZBS2001/13A. NIW A Client Report, Wellington. 28 p. Gust, N.; Inglis, G.J.; Hayden, B.; Floer!, O Surveillance for exotic marine organisms in New Zealand: Summer 2 ( ) surveillance. Research Progress Report for Ministry of Fisheries Research Proj ect ZBS , NIW A Client Report, Wellington. 12 p. (+maps). Inglis,GJ.; Gust, N Surveillance for exotic marine organisms in New Zealand: Winter I (2003) surveillance. Research Progress Report for Ministry of Fisheries Research Project ZBS2001/01, NIW A Client Report, Wellington. 9 p. (+maps) Smith, PJ.; Webber, W.R.; McVeagh, S.M.; Inglis, GJ.; Gust, N DNA and morphological identification of an invasive swimming crab, Charybdis japonica (A. Milne-Edwards, 1861), in New Zealand waters. N.z. J. Mar. Freshw. Res. 37: Webber, R. 2001: Space invaders: crabs that turn up in NZ unannounced. Seafood New Zealand. November

5 :r' '.-',...,~ <- "" Fig. 1. Charybdis japonica delimitation locations, April 2004,I.. '~,,- '"t :~:;~~~~Z;;~"":~\-::~"'i i:)"""<\{~."~' ""i'~<';';':'","~.,',',~:';,'""",", ~,~--'{: ~"{?fi~t,~... ;.,." ~~

6 Fig. 2. Sampling locations in Ngunguru estuary. locations. Roads are indicated in black, red crosses indicate sampling...! ' ~.".' ""::~~~~f;~~;fo'k\~."i. ~" o I I--IIIIII!I N A Kilometers :---1

7 Fig 3. Sampling locations in Pataua estuary. Roads are indicated in black, red crosses indicate sampling locations. N A x x x ". ":,~~, --1- '~. -;. ~ """:.

8 Fig. 4. Sampling locations in Ruakaka estuary. Roads are indicated in black, red crosses indicate trapping locations.,... :... ~~~ ':~_\,~~.. ~~'.J.: _.....;: ~ : :::5;'~:'~t:~,. ~'~ ':;-< ':',',~:r!.j'7:~':'-"::,-;;.-, ',~,~', '.,{.~., ~F;... -~1../~:~ Or,:,',;-.".- ',.~" ~ '-:~~:~}~~;:" ~,".' " ~,,"O,. - ~', :.y, i":.,, <,- :~.':;~ "L,.- ~~ ::~'..p: _>.w~.,: ':~~':"."l'1,~:~~-!-,~ :f - -:-'; /:i~~::~~(1~.~-: vo-,,'.-,~"',- "",.., '.. ~. "'... :'.,,'.-. ~ :~._~~:;~;r~:\~~!._~ ~ ;;'~:~~~)~:j.<~~~<-t~,;.i}/':~.;-.::'}:'-;',,,' x Xx Ruakaka o iiiiiiiliiliiiiiiliiliiiiiiliiliiiiiiliiliiiiiiliilrli ~~~~~ Kilometers "

9 Fig. 5. Sampling locations in Mangawhai estuary. Roads are indicated in black, red crosses indicate trapping locations. N A X i o Kilometers 1---I I

10 Fig. 6. Mean (+S.E.) numbers of native swimming crabs (Ova/pes catharus) and hairy handed crabs (Hemigrapsus crenulatus) per trap line in the four estuaries. Cl) C e L.. Cl) 0- L.. Cl)..c E :::J C C CO Cl) ~ T Ovalipes catharus I Hemigrapsus crenulatus ~ ~ :~,~~~:;:~~~:?:~;~yc ~ ~ Ilf{~~1 O~ ~ ~~~~~~ ~~ Ngunguru Pataua Ruakaka Mangawhai J

11 Fig. 7. Distribution of Ova/ipes catharus in Ngunguru estuary, April Crosses indicate absence, red points indicate presence. o...--' Kilometers

12 Fig. 8. Distribution of Hemigrapsus crenulatus in Ngunguru estuary, April Crosses indicate absence, red points indicate presence. -.. '... ' ~ ',';' \r '.,~.',...,,~~~),~t~l~"~'~;~~0:;' ~::.{t~(;~;~,.:.'; ~.( "t:~:.::? ~!;:/... ~--! I---I~_liIiiiiiIiirll ~~~ o Kilometers s

13 ,,1~" Fig 9. Distribution of Ovalipes catharus in Pataua estuary, April Crosses indicate absence, red points indicate presence., - ~'.~''''''~'''' ',...---I o Kilometers I---~

14 ".' f.,'..., Fig 10. Distribution of Hemigrapsus crenulatus in Pataua estuary, April Crosses indicate absence, red points indicate presence. xxx ex : '.':,:~.-:,.' " o, Kilometers

15 Fig 11. Distribution of Ovalipes catharus in ~uakaka estuary, April Crosses indicate absence, red points indicate presence.. : x Xx s o I Kilometers ~----I

16 Fig 12. Distribution of Hemigrapsus crenulatus in Ruakaka estuary, April Crosses indicate absence, red points indicate presence.,,->-->. \~ ",";! '" - ',- :,- _ :' '," f ~... '-;',:'..., ~ > ~,'" " 'I' :.,...,,~.,,,'~., '~-',~,.,:". '..., ~,...,~.:...,~.:: \ "': ! I----~ o '" '~ '~I.';... ;t;~\r;("~~;b~, 1.5 s Kilometers

17 Fig 13. Distribution of Ovalipes catharus in Mangawhai estuary, April Crosses indicate absence, red points indicate presence. s. ~.., o Kilometers ~~~I I I--'"

18 s o 5 Kilometers