Recruitment of Goby Postlarvae Into Hakalau Stream, Hawai'i Lsland Introduction

1 1

L. L. con

Stenogobius Stenogobius

ahina, ahina, Awaous

KUAMO'O KUAMO'O

13.46 13.46 mm SL.

G.K. G.K.

14.43 mm mm 14.43 SL,

were were most common after dark

occurred occurred throughout the 24-hour

23.61 23.61 mm SL and

936 936

Box Box

. .

P.O. P.O.

Introduction Introduction

Eleotris Eleotris sandwicensis,

Lentipes Lentipes conco/or,

A. A. guamensis

Hilo, Hilo, Hawai'i 9672/-0936

E. E. sandwicensis

Division Division Aquatic of Resources

recruited recruited most heavily immediately after sunrise

and and

NISHIMOTO NISHIMOTO AND DARRELL

Department Department of Land & Natural Resources

Hawaiian Hawaiian stream fishes are diadromous and re-enter

T. T.

14.09 mm mm 14.09 SL,

stimpsoni stimpsoni

49, 49, 1997

15.95 mm mm 15.95 SL,

S. S.

ROBERT ROBERT

hawaiiensis hawaiiensis

hinana, hinana, Sicyopterus stimpsoni,

symposium symposium on freshwater gobies

and and

30(1): 41 30(1):

ASIH ASIH

1 1

The The fish fauna occupying Hawaiian streams have low species diversity and

In In comparison to US mainland streams, Hawaiian freshwater ecosystems are 1995) 1995) with passive a trap set at the stream mouth. Postlarvae of all native

subsequent subsequent freshets.

cruitment cruitment into streams was greatest after periods of heavy rainfall and

and and during the rising tide.

period period but with recruitment peaks around the high tides. Postlarval re

classes: classes:

Hakalau Hakalau stream did not vary over the sample period. There were two size while while S.

stream stream fish species were collected and the mean fish size at entry into color color

hawaiiensis, hawaiiensis,

24-hour 24-hour period for 19 consecutive months (December 1993 to June

oceanic oceanic larval phase. Recruiting postlarvae were sampled hourly over a

streams streams as either clear, opaque or pigmented postlarvae after their

Abstract-Native Abstract-Native

guamensis, guamensis,

Recruitment Recruitment of Goby Postlarvae into Hakalau Stream, Hawai'i lsland

seasonal seasonal storms. Consequently, perennial streams are limited to the windward side

of of the main Hawaiian Islands ). (Fig. These streams 1 are characterized by having

high high degree of endemism, characteristic of island ecosystems (Fitzsimons &

islands' islands' receiving persistent orographic rainfall associated with trade winds and

sandbar sandbar berm fronting the estuary. The flow of water in streams depends upon the as as its return to normal flow.

sheds, sheds, flow directly downslope, and enter the ocean via a terminal waterfall or a flashy flashy flows dependent on rainfall patterns. The onset of a freshet flow is as abrupt

occurring occurring small lakes, freshwater habitats consist of 376 small, precipitous moun

quite quite small and less obvious than their marine counterpart. Except for 5 naturally

tain tain streams (Hawaii Stream Assessment 1990) that originate in rainforest water Micronesica Micronesica

Lentipes concolor concolor Lentipes

where courtship and egg-laying occurs. Attached eggs hatch within 24 to 70 hours hours 70 to 24 within hatch eggs Attached occurs. egg-laying and courtship where

tions as high as 3,000 ft. ft. 3,000 as high as tions

sea where they undergo development. After several months, these fishes recruit recruit fishes these months, several After development. undergo they where sea

ent. The remaining three species, species, three remaining The ent.

Nishimoto 1991). The entire compliment of Hawaiian stream fishes consists of of consists fishes stream Hawaiian of compliment entire The 1991). Nishimoto

(Kido (Kido

betimdaeyusra rmtesals aefl ihapeiios gradi a precipitous with waterfall smallest the from upstream immediately absent

adromous life cycle (Tate 1995). Juvenile and adult stages are spent in streams, streams, in spent are stages adult and Juvenile 1995). (Tate cycle life adromous

only five species, four gobies and one eleotrid (Table 1 1 (Table have eleotrid one and adults gobies four streams, In all only five ). species,

wicensis wicensis

a distinct instream distribution (Nishimoto & Kuamo'o 1991). 1991). Kuamo'o & (Nishimoto distribution instream distinct a

42 42

22"N 22"N

& &

19• 19•

Gobiidae Gobiidae

Eleotridae Eleotridae

Family Family

Figure I. Main Hawaiian Islands. Stippled areas represent the highest highest the represent areas Stippled Islands. Hawaiian Main I. Figure

160-W 160-W

1-----'-----''------_._ 1-----'-----''------_._

Heacock 1991, 1991, Lindstrom Heacock

and and

0 60km 60km 0

~ions ~ions

CJ-KA-,-U_A'_I CJ-KA-,-U_A'_I

Pacific Pacific

Stenogobius hawaiiensis hawaiiensis Stenogobius

of perennial streams streams perennial of

Table I. Native stream fishes inhabiting Hawaiian streams. streams. Hawaiian inhabiting fishes stream Native I. Table

cu i hs re adetn fr note anoet o eleva to rainforest the into far extend and order this in occur

Ocean Ocean

----+-----+------1-----+-----1 ----+-----+------1-----+-----1

(L. (L.

Awaous guamensis guamensis Awaous

Eleotris sandwicensis sandwicensis Eleotris

Stenogobius hawaiiensis hawaiiensis Stenogobius

Sicyoptems Sicyoptems

Lentipes conco/or conco/or Lentipes

concolor). concolor).

~ ~

Micronesica (30) I, I I 997 (30) I, Micronesica

Species Species

______

Awaous guamensis, Sicyopterus stimpsoni stimpsoni Sicyopterus guamensis, Awaous

& &

O'AHU O'AHU

stimpsoni stimpsoni

Brown 1994 1994 Brown to out swept are larvae ), and the

are common near sea level and are usually usually are and level sea near common are

LANA'I LANA'I

All Hawaiian freshwater fishes have a di a have fishes freshwater Hawaiian All

~ ~

MOLOKA'I MOLOKA'I

_,_ _,_

~ ~

______

KAHO'OLAWE KAHO'OLAWE

~ ~

CJ CJ

HAWAl'I HAWAl'I

_,__, _,__,

'o 'o

'o 'o 'opu

'o 'o

MAUI MAUI

'opu 'opu

Hawaiian Hawaiian name 'opu 'opu

'opu 'opu

naniha naniha

nopili nopili

alamo alamo

nlikea nlikea

hi hi

'a/mpa 'a/mpa

'okuhe 'okuhe

concentra

'ukole 'ukole

lors sand Eleotris

155

'o 'o

' '

(m) (m)

(f) (f) and and Nishimoto and Kuamo'o: Hawaiian Stream Goby Recruitment 43 back into streams, usually en masse, as postlarvae. The marine phase of S. hawai iensis lasts 119-150 days and that of A. guamensis lasts 151-164 days (Radtke et al. 1988). A subsistence :fishery for goby post larvae, collectively known by the na tive Hawaiians, as hinana or ahina, depending on size, was a favorite seasonal ac tivity, especially on the island of Kaua 'i. This practice is now illegal. This report describes patterns of recruitment for the five species of native Hawaiian stream gobies into a pristine perennial stream along the Hamakua Coast of the island ofHawai'i.

Study Site The study area was located at the mouth ofHakalau Stream, located about 15 miles north of Hilo just off of Highway 11. This stream originates in the rain forest on the northeastern flank of Mauna Kea and flows eastward for about 17 miles through native forest and agricultural lands and ends with an estuary where the ocean meets the stream. Because of the interactions between the tidal periods and the constant stream flow, a sand berm usually forms at the mouth of the stream. When the sand berm is present, the estuary's water level is higher than the ocean during low tides. A passive larval trap, designed and constructed by the second au thor (Kuamo'o, unpubl.) was positioned along the stream edge at the exit of the es tuary into the ocean. Recruiting goby postlarvae prefer the stream bank when recruiting inland and more often on the side with the fastest outflow current (C. Akuna, personal communication).

Sampling Method Recruiting goby postlarvae were sampled hourly over a 24-hour period for nineteen consecutive months from December 1993 to June 1995. Monthly sam pling was scheduled on the third quarter lunar phase, the period when hinana/ahina recruitment is heaviest (C. Akuna, personal communication, and 1996 Ancient Hawaiian Moon Calendar Related to Fishing and Farming). Sampling started at about sunrise and ended the following morning. Fishes in each hourly sample were euthanized immediately in ice water, iden tified to species, and measured with a dissection microscope and calipers. The specimens were then preserved in 5% buffered formalin. The samples are cata logued at the Museum of Natural Sciences, Louisiana State University. Water depth at the trap entrance was measured with a ruler, and the tidal heights were extrapolated from the tide chart published by a local fishing tackle shop. Since there are no stream gauges on Hakalau Stream, flow was proximated from daily rainfall data printed in the local newspaper.

Species Identification The identification of the five freshwater gobies were based on the structure of the pelvic fin, occurrence of notches in the upper lips, and arrangement of 44 Micronesica (30)1, 1997 melanophores in larvae and postlarvae (Tate et al. 1992, present study) (Fig. 2). Because freshly collected specimens were used to identify the species during the course of the sampling period, the distinct ventral melanophore pattern for each species of postlarva was the most useful characteristic. For E. sandwicensis, a sin gle mid-ventral row of melanophore extends from the isthmus through the pelvic fin base to the anal opening, and then continues posteriorly as two rows on each side of the anal fin. Stenogobius hawaiiensis has a single mid-ventral row of melanophores that extend from the isthmus just past the attachment of the pelvic disk and then continues posteriorly as a double row across the abdomen and on ei ther side of the anal fin. Awaous guamensis has a single mid-ventral row of melanophores from the isthmus to the middle of the pelvic disc attachment and then continues posteriorly as a double row. It also has a c-shaped "beard" formed by pig ment spots below its chin, which helps to distinguish this species from S. hawaiien sis. Sicyopterus stimpsoni is the largest of the postlarvae to enter the streams; these fish have a single mid-ventral row of melanophores reaching from the attachment of the pelvic disk to the bottom edge of the disk and two rows originating at the at tachment and extending just past the edge of the disk. Finally, Lentipes concolor has a conspicuous spot on the tip of its chin formed by a single large melanophore. These small fish also have a single mid-ventral row of melanophores that extends from the base of the pectoral fins posteriorly to the end of the pelvic disk.

Lentipes concolor Stenogobius hawaiiensis (14·16 mm SL) (13-15 mm SL)

Awaous guamensis Eleotris sandwicensis (15•17 mm SL) (12·14 mm SL)

Sicyopterus stimpsoni (22•24 mm SL)

Figure 2. Antero-lateral view of newly recruited stream goby postlarvae. Dashes represent melanophore patterns. Nishimoto and Kuamo'o: Hawaiian Stream Goby Recruitment 45

Newly recruited goby postlarvae are essentially clear-bodied ( except for the large eyes, internal organs and blood sinuses) when first entering the estuary. The tail is essentially forked but becomes progressively truncated and the body com pletely pigmented, as it metamorphoses from being part of the plankton commu nity to becoming essentially a bottom dweller in its adult habitat, a freshwater stream. Other morphological changes, such as the enlargement of the head in S. stimpsoni, will be described in detail by other authors in this volume.

Results and Discussion The postlarvae of all five species were present (Table 2). Except for S. hawai iensis, all of the other species were collected in at least 15 of the 18 monthly sam ples. Stenogobius was the least common numerically and collected in only 11 of the 18 monthly samples. The migration of the native goby postlarvae into Hakalau Stream seems to be size dependent (Fig. 3). The indigenous people ofHawai'i recognized two distinct size groups and differentiated them as: hinana which is S. stimpsoni and ahina which comprises the other four species. It was thought that the ahina were the runts and that the season for collecting postlarvae was over (C. Akuna, personal communication) when these sized larvae were collected in their nets. The hinana, S. stimpsoni, was significantly larger than the other species (Table 2, Fig. 3). The four species of ahina were similar in size but A. guamensis was consistently the largest and E. sandwicensis was always the smallest. The time of recruitment varied by species. Lentipes concolor and S. stimpsoni recruited heaviest immediately after sunrise (Fig. 4), A. guamensis continuing throughout the day and night (Fig. 5) and S. hawaiiensis and E. sandwicensis al most always recruited into the stream at night (Fig. 6). Upon entering the estuary, they rapidly change from opaque to pigmented and with a corresponding decrease in length. There may be as much as a 0.5 mm decrease in length between the clear and pigmented individuals. The hourly samples frequently had individuals from the same species ranging from clear to opaque to pigmented. The three upper-elevation gobies, L. concolor, S. stimpsoni and A. guamensis, actively seek fresh water once at the stream mouth. When the Lentipes catch was separated by pigmentation, the pigmented animals showed up earliest followed by the opaque individuals during the afternoon, and the clear specimens during the

Table 2. Recruiting native stream Goby postlarvae trap-collected monthly at the entrance to Hakalau Stream, Hawai'i Island, December 1993 to June 1995.

Total Total Mean size Standard Species number frequency (SL,mm) deviation

Lentipes concolor 1,645 43.6% 14.43 0.39 Awaous guamensis 1,167 30.9% 15.95 0.34 Eleotris sandwicensis 783 20.8% 13.46 0.38 Sicyopterus stimpsoni 117 3.1% 23.61 0.63 Stenogobius hawaiiensis 62 1.6% 14.09 0.52 46 Micronesica (30)1, 1997

30-.------,

E 25 _§_ • 'Hinana' :c • • • • • • • • I- • • • • • (.!:) • z • • □ l&nliW UJ ....J ~ 0 20 • cc I!,. ~ zc3 X Stenoaoblus I!,. I!,. I!,. I!,. I!,. I!,. + ~ CJ)~ I!,. I!,. I!,. I!,. I!,. I!,. I!,. I!,. z ~ □ 15 □ □ □ ~ ~ □ □ ~ 15 □ □ 'f 'Ahina' □ + 15 □X ~ ~ ~ ~ + + + + + + + + * + l + +

10 .,. .,. .,. .,. LO .,. .,. .,. .,. .,. .,. .,. LO U') U') U') U') U') 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, a, a, a, 0, 0, ~"' ~ ,.._ 0:, 0, .,. U') "' - "'- -"' ~ -LO "'- ----0 --"' ~ -"' -"' ---"' MONTH/YEAR

Figure 3. Mean standard lengths of goby postlarvae trap-collected at Hakalau stream, December 1993 to June 1995.

800 ,------, 60 -0-- Lentlpes --- Sicyopterus 50 en f.B 600 Zf a. ~ 40 ti: UJ ~ ....J Q ts en cc 400 30 UJ ts CD cc UJ :::E CD :::> :::E z :::> ....J z ~ ....J ~ ~ f2

o~NMV~~~~mo~NMV~~~~mo~NMV~ ~~~~~~~~~~NNNNNN HOURSAFTER SUNRISE

Figure 4. Diel occurrence of Lentipes and Sicyopterus postlarvae trap-collected at Hakalau stream, December 1993 to June 1995. Nishimoto and Kuamo'o: Hawaiian Stream Goby Recruitment 47

150 en 5

~<( ~ 100 coffi :E z:::> ....I ~ 50 12

O..-C\IM~~~~~mO,-C\IM~~~~~mo,-C\IMV~ ,- ,- ..- ,- ,- ,... ,- ,- ,- ,... C\I C\I N C\I N C\I

HOURSAFTER SUNRISE

Figure 5. Diel occurrence of Awaous postlarvae trap-collected at Hakalau stream, December 1993 to June 1995.

40 200 -0-- Stenogoblus Eleotris en ---- :::> en lri 30 150 0 8 w~ z w...J LL ~ 0 LL 20 100 a: 0 w a: co w :E CD :::> :E z z:::> ...J 10 50 ~ ~ ~ ~

0 0 o..-NMV~m~mmo..-C\IMV~~~mmo..-C\IMV~ ,...,...,...,...,...,...,...,...,...,...C\IC\IC\IC\IC'\IC\I HOURSAFTER SUNRISE

Figure 6. Diel occurrence of Stenogobius and Eleotris postlarvae trap-collected at Hakalau stream, December 1993 to June 1995. 48 Micronesica (30)1, 1997 highest diel tide. The pigmented and opaque individuals were the earlier settlers to the bottom and were at an advanced developmental stage and first to enter the es tuary. The bulk were the clear recruits, which were probably less developed and transported into the estuary with the highest diel tide. The other two species of go bies, S. stimpsoni and A. guamensis, show a similar trend. The two lower elevation species, S. hawaiiensis and E. sandwicensis, are the weakest swimmers. Unlike the other gobies, recruitment for these two species into the estuary only occurs during the nocturnal high tide or during high storm surf conditions, regardless of their developmental stage. Gaby recruitment into streams occurs year-round but is heaviest immediately after freshet flows and associated with periods of heavy rainfall (Fig. 7). Natural stream flows are a strong attraction to the inland migration of native Hawaiian stream fishes. Even intermittent streams on the leeward side of the island, which flow only after major storms, will immediately attract recruiting goby post larvae. The movement of these young fishes from the ocean into streams is the quintes sential link in completing the amphidromous life cycles for fishes and also for the major species of macroinvertebrates in Hawaiian streams. The migratory events described here for fishes from Hakalau stream are mirrored in streams throughout the high islands of the archipelago. This and similar studies underscore the singu lar significance of the connection between stream flow and amphidromy as the key to resource sustainability in freshwater ecosystems in the Hawaiian Islands.

1200 Ea ~ □ S!~ □ QgQbi!.1§ 1000 [D ~ ■ SiQllQ'1!~t!.!§ 0 .LmlliW 800 a: LU CD ::fi z=> 600 ~ ~ 400

200

0 (') ..,. ..,. ..,. ..,. ..,. ..,. ..,. ..,. ..,. ..,. ..,. ..,. 0, 0, 0, 0, Cl 0, 0, 0, 0, 0, Cl ~ ~ 0,"' Cl"' "'0, "'0, "'0, "'0, ;:;; ~ ;;; CX) 0 ~ ,-. 0, ~ (') ..,. ~ - -"' "' -"' - - - ~ "' - "' - - "' -"' MONTH/YEAR Figure 7. Monthly distribution of goby postlarvae by species trap-collected at Hakalau stream, December 1993 to June 1995. Nishimoto and Kuamo'o: Hawaiian Stream Goby Recruitment 49

Acknowledgment This project would have never progressed beyond the planning stage without the staunch support of W.S. Devick, Administrator of the Division of Aquatic Resource, DLNR. W. Ishikawa, S. Hau, G. Higashi provided specimens and anec dotal information about goby recruitment from the islands of Kaua'i, Maui and O'ahu. C. Akuna and the kupunas (elders) from Kaua'i are greatly appreciated for their willingness to share their vast personal knowledge of Hawaiian stream gob ies, to whom we dedicate this article. We thank J.M. Fitzsimons and B. Nishimoto for their valiant field support and the Colonel who provided sustenance, especially during the darkest hours before dawn.

References Fitzsimons, J.M. & R. T. Nishimoto. 1991. Behavior of gobioid fishes from Hawaiian fresh waters. In New Directions in Research, Management and Conservation of Hawaiian Freshwater Stream Ecosystems. Proceedings of the 1990 Symposium on Freshwater Stream Biology and Fisheries Resources, pp. 106-124, Division of Aquatic Resources, Honolulu. Hawaii Stream Assessment. 1990. A Preliminary Appraisal of Hawaii's Stream Resources. A cooperative project of the State of Hawaii, Commission on Water Resource Management and The National Park Service, Rivers and Trails Conservation Assistance Program. Honolulu, Hawaii. 294 pp. Kida, M.H. & D.E. Heacock. 1991. The spawning ecology of 'a 'opu-nakea (Awaous stamineus) in Wainiha River and other selected north shore Kauai rivers. In: New Directions in Research, Management and Conservation of Hawaiian Freshwater Stream Ecosystems. Proceedings of the 1990 Symposium on Freshwater Stream Biology and Fisheries Resources, pp. 142-157, Division of Aquatic Resources, Honolulu. Lindstrom, D.P. & C.L. Brown. 1994. Early development and biology of the am phidromous Hawaiian stream goby Lentipes concolor. Proceedings Fourth Inda-Pacific Fish Conference, Systematics and Evolution of Inda-Pacific Fishes, 28 November-4 December, 1993, Bangkok, Thailand. Nishimoto, R.T. & D.G.K. Kuamo'o. 1991. The occurrence and distribution of the native goby (Lentipes concolor) in Hawaii Island streams with notes on the distribution of other native fish species. In New Directions in Research, Management and Conservation of Hawaiian Freshwater Stream Ecosystems. Proceedings of the 1990 Symposium on Freshwater Stream Biology and Fisheries Resources, pp. 77-95, Division of Aquatic Resources, Honolulu. Radtke, R.L., R.A. Kinzie, III & S.D. Folsom. 1988. Age at recruitment of Hawaiian freshwater gobies. Environmental Biology of Fishes 23: 205-213. Tate, D.C. 1995. Behavioral and morphological development of immature Hawaiian freshwater fishes. PhD Dissertation, Louisiana State University, 98 pp. Tate, D.C., J.M. Fitzsimons & R.P. Cody. 1992. Hawaiian freshwater fishes (Osteichthyes, Gobiodei): a field key to the species of larvae and postlarvae during recruitment into fresh water. Occasional Papers of the Museum of Natural Science, Louisiana State University, No. 65, 10 pp.