Early Life History and Description of Larval Stages of an Amphidromous Goby, Sicyopterus Lagocephalus (Gobioidei: Sicydiinae)

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Early life history and description of larval stages of an amphidromous goby, Sicyopterus lagocephalus (Gobioidei: Sicydiinae)

Pierre Valade (1), Clara Lord (2), Henri Grondin (1), Pierre Bosc (1), Laura Taillebois (2), Midori Iida (3), Katsumi Tsukamoto (3) & Philippe Keith (2)

Abstract. - Sicyopterus lagocephalus is an amphidromous fish: adults live in rivers, but after hatching larvae are carried to the sea (dispersion stage). After a certain time spent at sea, post-larvae return to rivers to grow and reproduce. Sicy- opterus lagocephalus post-larvae recruiting to Reunion Island rivers (Mascarene Archipelago), provide an important food source to local populations and this fishing activity has a significant socio-economic impact. A better understanding of the early life traits of this species and the characterisation of larval stages should improve the biological and physiological knowledge needed to understand the processes involved in the dispersion stage and help managers to implement conservation measures. In Reunion Island, we characterised the development of larvae from hatching to migration to the sea. The results show that larvae do not undergo any development in freshwater, and that it is the arrival at sea that triggers the morphological transformations. Our results have also revealed that development is quicker when the temperature is high and that development varies according to water depth during the downstream migration. In natural temperature conditions, the maximum survival rate in freshwater is four days. This suggests that when the downstream migration takes too long because of anthropogenic or hydraulic factors, the free embryos would die before they reach the sea.

Résumé. - Premiers stades de vie et description des stades larvaires d’un gobie amphidrome, Sicyopterus lagocephalus (Gobioidei: Sicydiinae). Sicyopterus lagocephalus est un poisson amphidrome : les adultes vivent et se reproduisent en rivière. À l’éclosion les larves sont transportées en mer par le courant (phase dispersive), puis, après un certain temps, les post-larves retournent aux rivières et s’y installent. Lorsque les post-larves de Sicyopterus lagocephalus recrutent dans les rivières de La Réunion (archipel des Mascareignes), elles sont pêchées de façon intensive par la population locale et cette pêche a une grande importance socio-économique. Une meilleure connaissance des stades de vie précoces devraient permettre d’améliorer les connaissances biologiques et physiologiques nécessaires à la compréhension des processus impliqués dans la phase de dispersion de l’espèce, et ainsi aider à la mise en place de mesures de gestion. Nous avons caractérisé à l’île de La Réunion le développement des larves, depuis l’éclosion jusqu’à la migration vers la mer. Les résultats indiquent que celles-ci ne se développent pas en eau douce et que c’est l’arrivée en mer qui déclenche les transformations. Le développement est plus rapide lorsque la température est plus élevée et il varie selon la profondeur de l’eau. En conditions naturelles, le taux maximum de survie en eau douce est de 4 jours. Ceci suggère que si la dévalaison est trop longue, en raison de facteurs anthropi- ques ou hydrauliques, les embryons libres meurent avant d’atteindre la mer.

Key words. - Gobioidei - Sicyopterus lagocephalus- Reunion Island - Amphidromy - Larval stages - Dispersion.

In the tropical Indo-Pacific and the Caribbean regions, lution (Keith et al., 2000; Lord and Keith, 2006), but it is insular river systems are mainly colonised by Gobiidae extremely important to understand the processes involved (Sicydiinae). Their life cycle is adapted to the conditions in in the dispersion and colonisation of new habitats (Houde, these distinctive habitats, i.e., oligotrophic rivers that have 1989; Keith et al., 2005b) along with the internal and exter- formed relatively recently, that are subject to extreme season- nal factors governing these processes. al climatic and hydrological variations (Keith, 2003; Keith Amphidromous gobies contribute to a significant degree et al., 2005a). These species spawn in freshwater and the of diversity to the fish communities in the Indo-Pacific and free embryos drift downstream to the sea where they under- the Caribbean insular systems (Nelson et al., 1997; Watson go a planktonic phase before returning to the rivers to grow et al., 2002; Keith et al., 2007; Watson et al., 2007). Sicyop- and reproduce; they are called amphidromous (McDowall, terus lagocephalus is one of these gobies. At certain times 1997, 2007). The early life history of these species is poorly of the year, the biomass of post-larvae migrating upstream is known, as are the parameters leading to such extreme evo- so great that it provides an important source of food for local

(1) ARDA, route forestière de l’étang du Gol, 97427 Étang Salé, La Réunion. [[email protected]] (2) Muséum national d’Histoire naturelle, DMPA, Ichtyologie, UMR 7208, CP026, 57 rue Cuvier, 75231 Paris c e d e x 05, France. [[email protected]] (3) Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-Ku, Tokyo 164-8639, Japan.

Cybium 2009, 33(4): 309-319. Early life history of Sicyopterus lagocephalus Va l a d e e t a l .

Table I. - Conditions set to the different larval batches Hatching date for the study of the first larval stages in Sicyopterus Laying Batch Temperature - n n Age of transfer at sea lagocephalus. The larva age is indicated “Ex”, x being End of experiment ( ) ( ) (°C) the number of hours after hatching. A- 8 Dec. 1999 1 1 - - 1 2 - 1 3 - 20°C 11 Dec. 1999 2 4 - B- 21 Dec. 1999 3 5 - - 3 6 - 20°C 27 Dec. 1999 3 7 - C- 10 Jan. 2000 4 8 - - 4 9 - 4 10 - 20°C 14 Jan. 2000 4 11 E26 D- 24 Jan. 2000 5 12 E56 - 5 13 E56 5 14 E56 22°C 2 Feb. 2000 6 15 E4 E- 10 Apr. 2000 7 16 - - 7 17 - 7 18 E4 26°C 15 Apr. 2000 7 19 E4

an urgent need to improve our knowledge of the early life history of this species. The characterisation of the various stages should improve the biological and physiological knowledge needed to understand the processes involved in the dispersion phase and help managers to implement conservation measures (Lord and Keith, 2008; Keith and Mar- ion, 2002).

methods

Sicyopterus lagocephalus layings were collected under stones and sticked on them in the same sector of the Lan- gevin River (21°38.527 S.; 0.55°64.420 E.) in Reunion Island (Indian Ocean), between December 1999 and April Figure 1. - Sicyopterus lagocephalus egg just before hatching. Photo: ARDA 2000.

Description of larval development human populations (Bell, 1999; Watson et al., 2001; Keith We collected seven layings that were placed in individu- et al., 2004, 2006). This is the case in particular in Reun- alised tanks [circular, diameter 15 cm, 7 litres, water depth ion Island (Mascarene Archipelago, Indian Ocean). How- (H): 50 cm (mean river depth in the collected sites)] filled ever, harvesting of this food resource in estuaries is highly with water from the river. Water parameters were controlled unsustainable, on account of the complexity of the species’ to match the conditions in natural environment: natural pho- life cycle and the hydrological particularities of these islands toperiod; conductivity around 80 µS.cm-1; pH ranges from -1 (Delacroix, 1987). 7.0 to 9.0; O2 = 7-9 mg.l ; constant temperature although Recently, Keith et al. (2008) described the different ranging from 20 to 26°C between the various experiments. post-larval and juvenile stages of S. lagocephalus, in Reun- The five largest layings were divided into three or four equal ion Island when recruiting back to rivers. They established batches, therefore giving a total of 19 batches (Tab. I). Some a reference ontogenic scale for this species from the post- batches were kept in freshwater; others were transferred to larval marine stage to the adult freshwater stage. The pur- saltwater, in similar tanks filled with water collected at sea pose of this paper is to describe the various larval stages and for which the parameters were also controlled (natural of S. lagocephalus (Gobiidae: Sicydiinae), from hatching photoperiod and salinity; constant temperature ranging from to arrival at sea, to complete the reference scale. There is 20 to 26°C between the various experiments).

310 Cybium 2009, 33(4) Va l a d e e t a l . Early life history of Sicyopterus lagocephalus

Figure 2. - Sicyopterus lagocephalus larvae, in freshwater, 4 h after hatching (E4), with 0 h spent in seawater (0hSW), stage L1a. 1: otoliths, 2: yolk sac, 3: lipidic droplets, 4: notochord, 5: chromatophores, 6: caudal fin, 7: digestive tract, 8: early eye. Photo: ARDA

The larva age is written Ex, x being the number of hours Results after hatching. Different temperature conditions and times of transfer to saltwater have been imposed on the various Before hatching, the eggs measure 500 to 700 μm. Fig- batches (Tab. I). In order to describe their developmental ure 1 shows an isolated Sicyopterus lagocephalus egg just stage, photographs of larvae were taken every 6 hours, at before hatching (500 μm in diameter); the larvae can be seen given times: 2, 8, 14 and 20 h. The specimens were anaesthe- inside the egg. After hatching, the larvae measures 2 mm, it tised and were photographed using an image capture station is translucent, and many organs are already visible in out- composed of a binocular magnifier (Olympus SZ61; Olym- line. Figure 2 shows a larva 4 h after hatching (E4); the oto- pus Ltd, Paris) (magnification x8) coupled to a digital cam- liths, the yolks sac with the lipidic droplets, the notochord, era (Olympus C-5050; optical zoom x3; Olympus Ltd, Paris) the chromatophores (three to four according to the different linked to a computer. Each larva was then studied and meas- larvae), the caudal fin, and the digestive tract are all visible ured to the nearest tenth millimetre, using image processing in the larvae. software (ImageJ, v1.39, rsbweb.nih.gov/ij/). For the duration of the experiment, the larvae had their yolk sac (until Larval development in freshwater its absorption) and were not fed. The larvae were monitored For the batches maintained in freshwater, the larval development was monitored until the individual death. For until their death occurring either in freshwater or saltwater. each of these larval batches, no apparent modification has been noted. The various photos taken for each batch show Survival time of larvae in freshwater identical individuals: the yolk sac appears to incur no modi- During the experiments undertaken in freshwater, the fication, the mouth is closed, no fin appears, the chromato- survival time of larvae, corresponding to the presumedly phores do not extend and the eyes remain translucent. death of the last larvae in the batch, was logged. The deter- Figures 3 and 4 show the larvae just before their death, mined time corresponds to the maximum survival time for a respectively 62 h and 72 h old (20°C, H = 50 cm). Their larva at an imposed temperature and for a water depth (H) of morphology is identical to that of hatching larvae (Fig. 2). 50 cm. Therefore, larvae do not undergo any development in fresh- A series of additional experiments were performed to water, and seem to remain at the free embryo stage. determine the mortality of larvae according to temperature and water depth. Three columns of 600 ml (water depth Larval development in saltwater H = 9 cm) and one filled with 9 litres [circular, diameter The transfer of larvae to saltwater induces morphologi- 8 cm, water depth H = 200 cm] were filled with water from cal changes. In each experiment, the time of the first major the river; the conditions were controlled. One hundred lar- modification visible on the larvae was noted. According to vae were placed in each column. Dead larvae were counted water temperature, it was possible to define five larval stag- twice a day at 8 and 16 h and retrieved from the column with es (L1a to L1d and L2) (Figs. 2, 5-8; Tab. II) adapted and a glass pipette. modified from Bell (1994), Valade (2001) and Keithet al. This experiment was repeated five times, at three dif- (2008). Larvae at hatching (L1a) have no trace of eye, no ferent temperatures (20, 23, and 26°C). The larvae mortal- sign of jaw, are translucent and the yolk sac is at its maxi- ity was established as a percentage of dead larvae and as a mum size. Just after arrival at sea, larvae (L1b) have eyes on function of their age, the water depth and water temperature. the sides of the head and the posterior tip of the mandible is The larvae mortality at a given temperature is defined as the detectable as a bump or a prominence; yolk sac absorption lethal period 50% (PL50), which corresponds to the age of has begun. After 20 h to 40 h in seawater (hSW) and depend- the larvae when 50% of the individuals are dead. ing on the temperature, larvae (L1c) have lenses with early

Cybium 2009, 33(4) 311 Early life history of Sicyopterus lagocephalus Va l a d e e t a l .

Table II. - Description of the five larval stages observed forSicyopterus lagocephalus, at sea and without feeding for a 20-23°C water temperature. hSW: hours spent in sea water. Stages Description Figures Larvae at hatching; no trace of eye; no sign of jaw; translucent; yolk sac at its maximum size; L1a river stage. 2 Larvae just arriving to sea with 0-20 hSW according to the temperature. Early eye (trace of outer margin but no lens) or lens un-pigmented (lens present, retina unpigmented); eyes on lateral sides L1b of head; posterior tip of mandible detectable as a bump or prominence, approximately below eye; 5 translucent; beginning of the yolk sac absorption; marine stage. Free embryos Larvae with 20-40 hSW according to the temperature; lens early pigment (lens present and (L1) pigment beginning to appear on retina but no part of retina less transparent than smoked glass); L1c beginning of the migration of eyes in antero-lateral position of head; mouth appears formed, but 6 closed; appearance of pectoral fins; multiplication of chromatophores on the body; marine stage. Larvae with 40-65 hSW according to the temperature; lens pigmented (retina no longer translucent); eyes in antero-lateral position of head; mouth open in sub-inferior position; pectoral L1d fins in place; yolk sac same size as the eye; appearance of chromatophores in the cephalic area; 7 marine stage. Larvae with > 65 hSW; lens pigmented (retina no longer translucent); mouth seems to be well Larvae formed, open in terminal position and operating, ability to intake and to digest exogenous food; L2 L2 no more yolk sac; many chromatophores in the cephalic area and along the body; all internal 8 organs are in place; marine stage.

Table III. - Age and time spent in saltwater by larvae until they reach a certain developmental stage, without feeding, during the different experiments. hSW: hours spent in sea water. Stages Death Batch identification Age of transfer in sea water (SW) L1b L1c L1d L2 Batch 11 20°C E26 E41 15 hSW E65 39 hSW E71 45 hSW - E 83 57 hSW Batch 14 22°C E56 E68 12 hSW E92 36 hSW E119 63 hSW E146 90 hSW E200 144 hSW Batch 15 22°C E4 E14 10 hSW E32 28 hSW E56 52 hSW E92 88 hSW E200 196hSW Batch 18 26°C E4 E16 12 hSW E34 30 hSW E40 36 hSW E58 54 hSW E130 126 hSW Batch 19 E4 E16 12 hSW E34 30 hSW E40 36 hSW E58 55 hSW E130 126 hSW 26°C

Table IV. - Age of the larvae when 50% of the individual are dead (PL 50) and maximal survival there is no more yolk sac and all times for larvae in freshwater and for different temperatures and water depths. internal organs are in place (Tab. d: days; h: hours. II). Water depth Temperatures PL50 Maximum survival time Table III sums up, for each 20°C 65 h (2 d and 17 h) 90 h (3 d and 18 h) monitored batch and according to Column H = 9 cm 23°C 80 h (3 d and 8h) 96 h (4 d) the temperature, the age and time 26°C 36 h (1 d and 12 h) 48 h (2 d) spent in saltwater when the larvae Column H = 200 cm 23°C 40 h (1 d and 16 h) 65 h (2 d and 17 h) reach a new developmental stage, visible throughout these modifica- tions. pigment, the migration of eyes to the antero-lateral position In the experiment at 22°C, the larvae were transferred to of the head begins, the mouth is formed, but closed, and the saltwater at two different ages (E4 and E56), however, they pectoral fins appear. After 40 to 65 hSW, larvae (L1d) are reached the L1b to L2 stages after nearly the same time spent lens-pigmented and the eyes are in antero-lateral position of in saltwater. The developmental rate in saltwater therefore the head; the mouth is open in sub-inferior to terminal posi- seems to be independent of the larvae’s age (i.e., the time tion and the pectoral fins are in place. Finally, after 65 hSW spent in freshwater) when they arrive at sea, for a given tem- (2.5 days), larvae (L2) are lens-pigmented, the mouth seems perature. The time spent in freshwater therefore has no inci- to be well formed, open in terminal position and operating, dence on the development.

312 Cybium 2009, 33(4) Va l a d e e t a l . Early life history of Sicyopterus lagocephalus

3 4

6 5

7 8

Figure 3. - Sicyopterus lagocephalus larvae, in freshwater, 62 h after hatching, with 0 h spent in seawater (E62, 0hSW), stage L1a. Figure 4. - 72 h old larvae, in freshwater, with 0 h spent in seawater (E72, 0hSW), stage L1a. Figure 5. - 16 h old larvae, including 12 h spent in saltwater (E16, 12hSW), stage L1b. Figure 6. - 92 h old larvae, including 36 h spent in saltwater (E92, 36hSW), stage L1c. Figure 7. - 119 h old larvae, including 63 h spent in saltwater (E119, 63hSW), stage L1d. Figure 8. - 170 h old larvae, including 166 h spent in saltwater (E170, 166hSW), stage L2. Photos: ARDA

The final experiment was carried out at a much higher reserves at this stage, the lack of food leads to their death. temperature than for the latter two experiments (26°C vs 20°C and 22°C). This higher water temperature led to faster Survival time in freshwater according to temperature development of the larvae: transferred to SW at the same and water depth time (E4), they reached the L2 stage after 54 h spent at sea, The various experiments carried out in the water col- this period is nearly half that required by the larvae in water umns allowed us to establish mortality trend curves for the at 22°C (88 h). Moreover, in water at 26°C, the larvae died larvae according to freshwater temperature and water depth after 126 h spent in saltwater, which is 70 h less than for lar- (Fig. 9). For the different temperatures, the first deaths vae kept in water at 22°C (196 hSW). Water temperature has appear between 24 h and 48 h after hatching. an influence on the speed of development: the higher it is, Table IV sums up the PL50 evaluated according to the the quicker the development, and the sooner the larvae die. experimental conditions (temperature and water depth). In After the L2 stage, the larval development seems to come shallow depths (9 cm), the larvae show an optimal survival to a stop; they can however stay alive for more than 100 h at rate in freshwater for temperatures between 20 and 23°C. 22°C and 70 h at 26°C. As the larvae have finished their yolk The PL50 greatly decreases at higher temperatures. The

Cybium 2009, 33(4) 313 Early life history of Sicyopterus lagocephalus Va l a d e e t a l .

Table V. - Maximum survival times observed during the monitoring of larval development in freshwater, according to the storing temperature for H = 50 cm. d: days; h: hours. Experiments Temperature Maximum survival time A 20°C 74h (3d and 2h) B 20°C 86h (3d and 14h) C 20°C 77h (3d and 5h) D 22°C 62h (2d and 14h) E 26°C 46h (1d and 22h)

free embryo stage. It is newly hatched [≤ 2 mm total length (TL)], rheoplanktonic, non-feeding, with a yolk sac incompletely absorbed. The yolk-sac absorption only starts at sea. This larval stage comprises four parts (a to d) corresponding to eyes, fins and mouth development. Bell (1994) characterised the different larval growth stages of another freshwater Sicydiinae from Dominica (West Indies) (Sicydium spp.) and obtained similar results. He described the larval stages between hatching and migration to sea by observing the development of eye pigmentation and jaw development. Figure 9. - Mortality of Sicyopterus lagocephalus larvae for two He noted that newly hatched larvae of Sicydium punctatum water depths (H = 9 cm and H = 200 cm) in freshwater according to different temperatures. were approximately 1.8 mm in TL, and were at stages from eye with lens present and pigment beginning to appear on retina. In his study the mouth is incompletely developed optimal lethal period 50% for larvae in Reunion freshwater until three days. In Okinawa Island, southern Japan, Yama- (for a temperature between 20 and 23°C) is close to three saki and Tachihara (2006) have studied newly hatched lar- days. The first deaths appear from 24 h after hatching. The vae [1.20-1.32 mm notochord length (NL)] of Stiphodon maximal survival rate is between 3 and 4 days. percnopterygionus. They were poorly developed, with large The water depth has a significant effect on larvae mor- yolk sacs and unopened mouths. Three days after hatching tality. For a water temperature of 23°C, the larvae in the 2 [1.87-2.05 mm NL], eyes were fully pigmented and mouths m water column show a PL50 of 40 h, whereas those in the were open. In Rhinogobius sp. (Gobiidae), Hirashima and 9 cm water column show a PL50 of 80 h, which is twice as Tachihara (2000) noted that the yolk sac was completely much. In addition, the maximum survival rates observed consumed in three to seven days after hatching. In Awaous during the monitoring of the larval development for a water melanocephalus, Yamasaki and Tachihara (2007) showed, depth of 50 cm confirm these results (Tab. V). The water under controlled conditions [larvae reared in 50% sea water depth in the rivers seems to be an important factor affecting (salinity 20 ppt)], that newly hatched larvae [0.93-1.04 mm larvae survival. in total length (TL)] were poorly developed, lacking a mouth The maximal survival rates observed decrease as the and having a large yolk sac and unpigmented eyes. The temperature increases. At 26°C, the effect of the water depth mouth and anus had not yet formed. One day after hatch- becomes insignificant compared to the effect of the tempera- ing, the yolk sac was reduced in size and the pectoral fin bud ture; indeed the maximal survival rate is identical for water was apparent. Two days after hatching, larvae had grown to depths of 9 and 50 cm. 1.49-1.60 mm TL, the yolk was further reduced and the pigmentation of eyes had begun. Three days after hatching, the mouth and anus were open, the gas bladder appeared and the Discussion eyes became fully pigmented (1.88-2.10 mm TL). The yolk sac was completely absorbed 5 days after hatching at a water Our study characterises the early developmental stages of temperature of 27-28°C, and no larvae survived beyond this Sicyopterus lagocephalus from hatching to migration to the stage corresponding to 120 hSW. In our study, no larvae sur- sea by monitoring changes for eyes, pigmentation, fins, yolk vived after 126 hSW. sac size and mouth. We have described 5 stages from L1a During the last larval stage (L2), larvae of Sicyopterus to L1d to L2 (Tab. II) for a water temperature of 20-23°C lagocephalus acquire the ability to intake and digest exog- (natural condition in Reunion Island). The L1 stage is the enous food and the yolk sac is completely absorbed. Com-

314 Cybium 2009, 33(4) Va l a d e e t a l . Early life history of Sicyopterus lagocephalus pleting the study made by Keith et al. (2008) on post-larvae and Mizuno (1999) suggested that early starvation of larvae and juveniles, the present work now provides a nearly com- limits reproductive success of fish located far from the sea, plete ontogenic reference scale from hatching to recruitment which would result in strong selection for fish reproduction in freshwater. The morphological transformation of S. lago- in certain regions of rivers within a given distance from the cephalus between hatching and adult phase is composed of sea. Tamada and Iwata (2005) have studied newly hatched two larval stages (L1a to d, L2, this study), three post-larval Rhinogobius sp. CB (cross-band type). Since larger and stages (PL0 to PL2) and two juvenile stages (J1, J2) (Keith older individuals usually inhabit the upper reaches of rivers, et al., 2008). However, the morphological changes between larvae from larger females are more likely to suffer higher L2 and PL0 must be better studied by catching larvae at sea. risks of starvation or predation during their longer migra- Our work shows that larvae do not undergo any devel- tion to the sea. Tamada and Iwata (2005) have measured egg opment in freshwater, where they remain at the same stage, volumes and clutch sizes, as well as larval starvation toler- holding off any development until their arrival at sea, where ance. They noted that there was a significant positive cor- the transfer to saltwater triggers the series of larval trans- relation between egg size and the 72-hour survival rate of formations for Sicyopterus lagocephalus, namely the fin unfed hatchlings. Intra-specific variation of egg volumes development and the opening of the mouth. Some other and clutch sizes in this species seems to be an adaptation for authors have demonstrated that newly hatched larvae are enhancing offspring survivorship during migration to the sea better adapted physiologically to life in seawater, while pro- (McDowall, 2007). Success for Sicyopterus life cycle is in longed exposure to freshwater postponed development and part a question of getting as many larvae as possible trans- increased mortality markedly (Lindstrom and Brown, 1994; ported downstream, established, feeding and growing in the Valade, 2001; Yokoi and Hosoya, 2005). Bell and Brown marine environment, before their endogenous energy sup- (1995) also showed that there is an active salinity choice by ply (provided by the yolk) becomes exhausted (McDowall, the vesiculate larvae of Sicydium punctatum in Dominica 2009). (West Indies). In our experimental conditions, the larvae of S. lago- In our study, the speed of the larval development in salt- cephalus have an optimal survival time in freshwater for water seems to be independent of the time spent in freshwa- temperatures held between 20 and 23°C, which corresponds ter before reaching the sea. One of the consequences of this to the mean daily temperatures in the Langevin River dur- is a limited life time in freshwater for Sicyopterus lagoce- ing reproduction (upstream: 19°C, downstream: 23°C). phalus. In Sicydium spp. larvae, Bell and Brown (1995) and The age of the larvae when 50% of the individuals are dead Bell (2007) thought that mortality in freshwater cannot be (PL50) greatly decreases for higher temperatures, whatever due to lack of available food and must be a result of the ina- the depth: the optimal PL50 for larvae in freshwater is three bility of the larvae to develop beyond an early stage in these days. At these temperatures (20 to 23°C), the first deaths environments before becoming inactive. On the other hand, appear 24 h after hatching, mortality is total after four days in their saline treatments, Bell and Brown (1995) noted that in freshwater. Ego (1956) reported that larvae of Awaous the yolk exhaustion is coupled with more complete devel- guamensis placed in seawater (34 ppt) lived up to eight days, opment of larvae suggesting that mortality of larvae may while larvae in freshwater lived only four days. Gymnogo- have resulted from starvation. Moriyama et al. (1998) esti- bius urotaenia, with large larvae [5.3 mm TL at hatch], is mated that in normal or low river flow, embryos from the reported to possess chloride cells soon after hatching, and upstream reaches die of starvation before they reach the sea. larvae kept in 50% seawater lived more than 30 days while Since there is practically no food available for drifting lar- those in freshwater lived less than seven days (Katsura and vae, extended downstream migration may enhance the risk Hamada, 1986). Todd (1975) reported that larvae of Dormi- of starvation. Iguchi and Mizuno (1999) hypothesized that tator latifrons ceased to swim 68 h in nearly fresh (3 ppt) early survival of amphidromous fish varies among popula- water. Yokoi and Hosoya (2005) have studied the larval tions according to the length of the river, due to its effect salinity tolerance for the endangered amphidromous goby, on larval starvation. This hypothesis was tested with the Rhinogobius sp. BI, an amphidromous endemic to the Bonin common Japanese amphidromous goby, Rhinogobius brun- Islands. They showed that hatching larvae could generally neus. Based on morphological characteristics, larvae were survive for 72 h under any salinity conditions. However, categorized as being in an endogenous feeding state (EFS) all individuals died after 144 h in 100% artificial seawater, or irrecoverable starved state (ISS). The frequency of ISS whereas over 60% survived for a longer term in freshwater larvae in the population from a long river was nearly twice and 50% artificial seawater. However, larval numbers fell the frequency in the population from a short stream. More drastically ca. 40 days after hatching in 50% artificial seawa- than half of larvae were judged to be dying during down- ter. Such a reduction in number indicates a critical depletion stream migration in the comparatively long river, although period in the early developmental stages. Finally, Bell and this was possibly an underestimation. As a result, Iguchi Brown (1995) showed that swimming endurance was mar-

Cybium 2009, 33(4) 315 Early life history of Sicyopterus lagocephalus Va l a d e e t a l . ginally longer in seawater than in freshwater, and the great- Foster and Fuiman, 1987). est swimming endurances were in haloclines. The preference The larvae of S. lagocephalus have completed their shown by larvae in haloclines for low salinities is consistent development at the L2 marine stage, the organs are in place, with their superior swimming endurance compared to larvae and the yolk sac is completely absorbed. They are then in freshwater or seawater treatments and, therefore, suggests capable of feeding. This is the last stage of our experiment. an adapted response to the downstream migration. According to Keith et al. (2008), the larva is competent when We showed that the seawater temperature has an influ- it is morphologically and physiologically capable of colonis- ence on the speed of larval development, which is quicker at ing freshwaters; the larva is able to respond to a signal trig- 26°C than at 22°C. Although the basic sequence of embryon- gering the processes leading to recruitment (i.e., beginning ic developmental events was maintained at different temper- of the morphological transformation and migration towards atures, there was some delay in the timing of the appearance the coast). From then on, after the L2 stage, they are referred of some structures at lower temperatures; this phenomenon to as post-larvae (PL0) subject to the colonisation signal in fish development has been known for some time (Blax- (Keith et al., 2008). Nevertheless the morphological changes ter, 1969). In the Gobiidae Gobius cobitis, the embryonic between L2 and PL0 stages (a long period of 4 to 6 months) development was studied at two temperature ranges (12- must be better studied by catching larvae at sea. But where 16°C and 15-18°C), and was faster at higher temperatures are these L2 and PL0 larvae when at sea? Do they stay near (Gil et al., 1997; Borges et al., 2003). For Gobius paganel- the coast or are they far away from rivers in the open sea? At lus, the basic sequence of larval development was similar at this stage, nobody really knows and nobody knows how they different temperatures, being faster at higher temperatures, feed. Sorensen and Hobson (2005) used stable isotope anal- and the larvae reached a similar size at the completion of ysis to evaluate the sources of nutrients used by amphidro- development regardless of temperature (Borges et al., 2003). mous gobiid fishes (Lentipes concolor, Sicyopterus stimpso- Finally, Fukuhara (1990) showed that for Rhinogobius brun- ni, Awaous guamensis) caught migrating into and living in neus consumption of yolk is regulated by metabolism, which Hakalau Stream, Hawaii (United States). Although consider- varies according to water temperature and other physical able variation amongst the stable isotope values of stream factors. The temperature has crucial role in the duration of items was noted across all four years of the study, the rela- each phase between L1b and L2. This factor could explain tionships between the fishes were relatively constant. Stable the variability of the pelagic larval duration in Sicyopterus isotope values of recruiting gobies were consistently closer and its seasonality (Lord et al., 2010). to those of both inshore plankton and freshwater adults In our study the depth difference, at a given tempera- than those of offshore plankton, suggesting that the larvae ture, has an effect on larval mortality. So, in rivers, the water of these species derive much of their nutrition from inshore depth could act as an important factor for larval survival. In environments influenced by fresh water (Sorensen and Hob- shallow water, the swimming effort would be far less com- son, 2005). Small differences between the stable values of pared to that made by the larvae to maintain itself in a great- these species further suggested that their larvae come from er water mass, in which larvae would therefore tire more different inshore locations. However, in their interesting quickly, thus reducing their survival. Indeed, in previous study, Sorensen and Hobson (2005) did not integrate the time studies on Sicyopterus, just after hatching, L1a larvae have necessary to metabolise the nutrients, i.e., how long the lar- a characteristic behaviour during their downstream migra- vae have been under the influence of inshore nutrients. They tion. Free embryo of Sicyopterus stimpsoni from Hawaii and have only worked on specimens caught migrating into and of S. lagocephalus from Reunion Island “swim” repeatedly living in the stream and have concluded that the larvae spent upwards until they contact the water surface, then for a while their early life near the river mouths. Their study shows that cease “swimming” and sink and then move towards the sur- competent larvae are liable to spend a certain amount of time face again (Kinzie, 1993; Keith et al., 1999; Valade, 2001). in front of the river mouth in order to wait for appropriate With such behaviour, a deep river could be more energy recruiting conditions. How far larvae drift from their natal consuming. This behaviour facilitates their transport to the river cannot be estimated. To date one can only propose vari- sea (Balon and Bruton, 1994). Larvae of Sicydium punc- ous scenarios concerning the marine planktonic stage of lar- tatum remain in the water column by alternately swimming vae: it is unknown if larvae are retained close to shore or are upward and sinking, and are passively carried toward the sea transported out to sea (Murphy and Cowan, 2007). Recent by river currents (Bell, 1994). This passive seaward trans- molecular and otolith studies on Sicyopterus japonicus con- port to coastal nursery areas would be promoted by keeping cluded that the larvae are capable of drifting in large oceanic larvae suspended in the river flow (Bell and Brown, 1995). currents in an offshore environment, transporting the larvae This ‘swim-up/sink-down’ behaviour has also been observed from the southern to the northern parts of the species’ range in several related gobies: Awaous guamensis, Dormitator (Watanabe et al., 2006; Iida et al., 2008; Iida et al., 2010). latifrons, and Evorthodus lyricus (Ego, 1956; Todd, 1975; We will learn more about the marine planktonic phase once

316 Cybium 2009, 33(4) Va l a d e e t a l . Early life history of Sicyopterus lagocephalus we manage to catch larvae at sea. after recruitment in freshwaters (Keith et al., 2008). In conclusion, the results obtained in our work add sig- Finally, the physiological state of each larval stage of nificant information to the study of fish populations, thereby S. lagocephalus can now also be characterised, as can the providing managers with precise knowledge of the develop- hormones responsible for triggering downstream migra- mental state while monitoring gobiid populations. Indeed, tion and morphological transformation. Moreover, it would transformations between hatching and marine migration have be beneficial to assess the duration of the L1 (b to d) and been characterised precisely thereby completing the refer- L2 stages, by catching larvae at sea, in order to describe the ence scale elaborated by Keith et al. (2008). The morphologi- pelagic stages between L2 and PL0, and allowing spatio- cal transformation of S. lagocephalus between hatching and temporal modelling of the oceanic dispersal. the adult phase is therefore composed of five larval stages (L1a-d, L2) (this study, and awaiting the description of the Acknowledgments. - We would like to thank the staff of ARDA pelagic larval stages between L2 and PL0), three post-larval (Association Réunionaise pour le Développement de l’Aquaculture) stages (PL0 to PL2) and two juvenile stages (J1, J2) previ- for their help during fisheries and experiments, particularly Y. Zitte ously defined by Keithet al. (2008). After hatching, the free and J.F. Ricou, and the Provincial and Territorial authorities of Reunion Island and New Caledonia for facilitating the research on embryo passively drifts to the sea (Stage L1). The shift to Sicyopterus species (permit 1224.08/PPS). We extend our thanks to salt water triggers the first transformations corresponding to D. Lord for re-reading this paper. the development of the eyes, fins and mouth. When the lens is pigmented, the mouth open and operating, it then becomes an L2 larva. This larval phase ends when all the temporary References embryonic and larval organs disappear and are replaced by Balon E.K. & Bruton M.N., 1994. - Fishes of the Tatinga rudimentary structures that are characteristic of post-larvae River, Comoros, with comments on freshwater amphidromy in subject to the colonisation signal (Keith et al., 2008). the goby Sicyopterus lagocephalus. Ichthyol. Explor. Freshw., Murphy and Cowan (2007) have shown that the mech- 5: 25-40. anism of larval production, retention, dispersal to sea, and Bell K.N.I., 1994. - Life cycle, early life history, fisheries and recruitment to freshwater are both governed by biologi- recruitment dynamics of diadromous gobies of Dominica, W.I., emphasising Sicydium punctatum Perugia. Ph.D. Thesis, 275 p. cal and physiological processes. Our study has pointed out Memorial Univ. of Nfld. St. John’s. the role of the duration of the larval downstream migration Bell K.N.I., 1999. - An overview of goby-fry fisheries. Naga and of water’s physical parameters (temperature and depth) ICLARM Quart., 22: 30-36. on the larval development and survival. The life cycle and Bell K.N.I., 2007. - Opportunities in stream drift: methods, goby migration of amphidromous species are critically depend- larval types, temporal cycles, in situ mortality estimation, and ent on the integrity of the mountain-river-ocean corridor. conservation explanations. Bish. Mus. Bull. Cult. Environ. Anthropogenic alterations of the environment may have Stud., 3: 35-61. an impact on the performance of species and on their abil- Bell K.N.I. & Brown J.A., 1995. - Active salinity choice and ity to migrate to the sea: for example, adding obstacles in enhanced swimming endurance in 0-8 day old larvae of diadromous gobies, including Sicydium punctatum (Pisces), in Domi- the watershed (e.g., dams) will increase the duration of the nica West Indies. Mar. Biol., 121: 409-417. downstream migration after hatching and so the mortality Blaxter J.H.S., 1969. - Development: eggs and larvae. In: Fish rate of larvae. Some major climatic events, increasing the Physiology, Vol. 3 (Hoar W.S. & Randall D.J., eds.), pp. 178- depth and the velocity of rivers, like heavy rains, or decreas- 252. New York: Academic Press. ing this depth, like drought, could positively or negatively Borges R., Faria C., Gil F., Gonçalves E.J. & Almada impact the downstream migration and the survival of larvae. V.C., 2003. - Embryonic and larval development of Gobius Other anthropogenic impacts on streams, like pollution or paganellus (Gobiidae). J. Mar. Biol. Ass. UK., 83: 1151-1156. deforestation, could also diminish the flow rates and alter Brasher A.M.D., 2003. - Impact of human disturbances on biot- ic communities in Hawaiian streams. Bioscience, 53: 1052- downstream larval migration and dispersion, and therefore 1060. the recruitment success (Houde, 1989; Brasher, 2003; Lord Delacroix P., 1987. - Étude des “bichiques”, juvéniles des Sicy- and Keith, 2008). Derivation channels on the main river flow opterus lagocephalus (Pallas), poissons Gobiidae migrateurs could also act as significant trap for early life stages. des rivières de la Réunion (Océan Indien) : exploitation, répar- Growing urbanisation in Reunion Island is driving the tition, biologie de la reproduction et de la croissance. Ph.D. need for water supply and electricity. The water basins are Thesis, 144 p. Univ. de La Réunion, St Denis. subject to extensive change and destruction, but the species’ Ego K., 1956. - Life history of freshwater gobies. In: Freshwater Gamefish Management Research, Project No. 4-4-R, pp. 1-23. amphidromous life cycle means it is important to maintain Honolulu: Department of Land and Natural Resources. the mountain-ocean corridor, on the one hand, for the lar- Foster N.R. & Fuiman L.A., 1987. - Notes on the behaviour vae’s downstream migration after hatching and, on the other and early life history of Evorthodus lyricus. Bull. Mar. Sci., 41: hand, for the post-larval and juvenile upstream colonisation 27-35.

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Fukuhara O., 1990. - Effects of temperature on yolk utilisation, Keith P., Hoareau T., Lord C., Ah-Yane O., Gimmon- initial growth, and behaviour of unfed marine fish-larvae.Mar. eau G., Robinet T. & Valade P., 2008. - Characterisation Biol., 106: 169-174. of post-larval to juvenile stages, metamorphosis, and recruit- Gil M.F., Gonçalves E.J., Faria C., Almada V.C., ment of an amphidromous goby, Sicyopterus lagocephalus Baptista C. & Carreiro H., 1997. - Embryonic and lar- (Pallas, 1767) (Teleostei: Gobiidae: Sicydiinae). Mar. Freshw. val development of the giant goby Gobius cobitis (Gobiidae). J. Res., 59: 876-889. Nat. Hist., 31: 799-804. Kinzie III R.A., 1993. - Reproductive biology of an endemic, Hirashima K. & Tachihara K., 2000. - Embryonic develop- amphidromous goby Lentipes concolor in Hawaiian streams. ment and morphological changes in larvae and juveniles of two Environ. Biol. Fish., 37: 257-268. land-locked gobies, Rhinogobius spp. (Gobiidae), on Okinawa Lindstrom D.P. & Brown C.L., 1994. - Early development Island. Jpn. J. Ichthyol., 47: 29-41. and biology of the amphidromous Hawaiian stream goby Len- Houde E.D., 1989. - Subtleties and episodes in the early life of tipes concolor. In Systematics and Evolution of Indo-Pacific fishes.J. Fish. Biol., 35(A): 29-38. Fishes. Proceedings of the Fourth Indo-Pacific Fish Confer- ence, pp. 397-409. Bangkok, Thailand: Faculty of Fisheries. Iida M., Watanabe S., Akira S. & Tsukamoto K., 2008. - Recruitment of the amphidromous goby Sicyopterus japoni- Lord C. & Keith P., 2006. - Threatened fishes of the world:Pro - cus in the estuary of the Ota River, Wakayama, Japan. Environ. togobius attiti (Watson & Pöllabauer, 1998) (Galaxiidae). Envi- Biol. Fish., 83: 331-341. ron. Biol. Fish., 77: 101-102. Iida M., Watanabe S., Yamada Y. , Lord C., Keith P. & Lord C. & Keith P., 2008. - Threatened fishes of the world: Tsukamoto K., 2010. - Survival and behavioral character- Sicyopterus sarazini Weber and De Beaufort (Gobiidae). Envi- istics of amphidromous goby larvae of Sicyopterus japonicus ron. Biol. Fish., 83: 169-170. (Tanaka, 1909) during their downstream migration. J. Exp. Lord C., Brun C., Hautecoeur M. & Keith P., 2010. - Mar. Biol. Ecol., 383: 17-22. Comparison of the duration of the marine larval phase estimat- Iguchi K. & Mizuno N., 1999. - Early starvation limits survival ed by otolith microstructural analysis of three amphidromous in amphidromous fishes.J. Fish. Biol., 54(4): 705-712. Sicyopterus species (Gobiidae: Sicydiinae) from Vanuatu and New Caledonia: Insights on endemism. Ecol. Freshw. Fish., 19: Katsura K. & Hamada K., 1986. - Appearance and disappear- 26-38. ance of chloride cells throughout the embryonic and postem- bryonic development of the goby, Chaenogobius urotaenia. McDowall R.M., 1997. - Is there such a thing as amphidromy? Bull. Fac. Fish. Hokkaido. Univ., 37: 95-100. Micronesica, 30: 3-14. Keith P., 2003. - Review paper: Biology and ecology of amphidr- McDowall R.M., 2007. - On amphidromy, a distinct form of omous Gobiidae of the Indo-Pacific and the Caribbean regions. diadromy in aquatic organisms. Fish Fish., 8: 1-13. J. Fish. Biol., 63: 831-847. McDowall R.M., 2009. - Early hatch: A strategy for safe down- Keith P. & Marion L., 2002. - Methodology for drawing up a stream larval transport in amphidromous gobies. Rev. Fish Biol. Red List of threatened freshwater fish in France.Aquat. Cons., Fish., 19: 1-8. 12: 169-179. Moriyama A., Yanagisawa Y., Mizuno N. & Omori K., Keith P., Vigneux E. & Bosc P., 1999. - Atlas des poissons et 1998. - Starvation of drifting goby larvae due to retention of crustacés d’eau douce de La Réunion. Patrim. Nat., 39: 1-136. free embryos in upstream reaches. Environ. Biol. Fish., 52: 321-329. Keith P., Watson R.E. & Marquet G., 2000. - Découverte d’Awaous ocellaris (Broussonet, 1782) (Perciformes, Gobii- Murphy C.A. & Cowan J.H., 2007. - Production, marine larval dae) en Nouvelle-Calédonie et au Vanuatu et conséquences retention or dispersal, and recruitment of amphidromous biogéographiques. Cybium, 24(4): 350-400. Hawaiian gobioids: Issues and implications. Bish. Mus. Bull. Cult. Env. Stud., 3: 63-74. Keith P., Watson R.E. & Marquet G., 2004. - Sicyopterus aiensis, a new species of freshwater goby from Vanuatu (Tele- Nelson S.G., Parham J.E., Tibatts R.B., Camacho F.A., ostei: Gobioidei). Cybium, 28: 111-118. Leberer T. & Smith B.D., 1997. - Distribution and micro- habitats of the amphidromous gobies in streams of Micronesia. Keith P., Hoareau T. & Bosc P., 2005a. - A new species of Micronesica, 30: 83-91. freshwater goby (Pisces: Teleostei: Gobioidei) from Mayotte Island (Comoros) and comments about the genus Cotylopus Sorensen P.W. & Hobson K.A., 2005. - Stable isotope analy- endemic to Indian Ocean. J. Nat. Hist., 39: 1395-1405. sis of amphidromous Hawaiian gobies suggests their larvae spend a substantial period of time in freshwater river plumes. Keith P., Galewski T., Cattaneo-Berrebi G., Hoar- Environ. Biol. Fish., 74: 31-42. eau T. & Berrebi P., 2005b. - Ubiquity of Sicyopterus lagocephalus (Teleostei: Gobioidei) and phylogeography of the Tamada K. & Iwata K., 2005. - Intra-specific variations of egg genus Sicyopterus in the Indo-Pacific area inferred from mito- size, clutch size and larval survival related to maternal size in chondrial cytochrome b gene. Mol. Phyl. Evol., 37: 721-732. amphidromous Rhinogobius goby. Environ. Biol. Fish., 73: 379-389. Keith P., Lord C. & Vigneux E., 2006. - In vivo observations on postlarval development of freshwater gobies and eleotrids Todd E.S., 1975. - Vertical movements and development of the from French Polynesia and New Caledonia. Ichthyol. Explor. prolarvae of the eleotrid fish, Dormitator latifrons. Copeia, Freshw., 17: 187-191. 1975: 564-568. Keith P., Marquet G. & Watson R.E., 2007. - Stiphodon Valade P., 2001. - Étude de la biologie de reproduction et des kalfatak, a new species of freshwater goby from Vanuatu (Tele- premiers stades larvaires des cabots bouches ronde à l’île de La ostei: Gobioidei: Sicydiinae). Cybium, 31(1): 33-37. Réunion. Master’s Thesis, Univ. de La Réunion.

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Watanabe S., Iida M., Kimura Y., Feunteun E. & Tsu- Yamasaki N. & Tachihara K., 2006. - Reproductive biology kamoto K., 2006. - Genetic diversity of Sicyopterus japoni- and morphology of eggs and larvae of Stiphodon percnoptery- cus as revealed by mitochondrial DNA sequencing. Coast. Mar. gionus (Gobiidae: Sicydiinae) collected from Okinawa Island. Sci., 30: 473-479. Ichthyol. Res., 53: 13-18. Watson R.E., Keith P. & Marquet G., 2001. - Sicyopus Yamasaki N. & Tachihara K., 2007. - Eggs and larvae of (Smilosicyopus) chloe, a new species of freshwater goby from Awaous guamensis (Teleostei:Gobioidei). Ichthyol. Res., 54: New Caledonia (Teleostei: Gobioidei: Sicydiinae). Cybium, 89-91. 25(1): 41-52. Yokoi K. & Hosoya K., 2005. - Larval salinity tolerance in the Watson R.E., Keith P. & Marquet G., 2002. - Lentipes endangered goby Rhinogobius sp. BI (Gobiidae) from the kaaea, a new species of freshwater goby from New Caledonia Bonin Islands. Jpn. J. Ichthyol., 52: 31-34. (Teleostei: Gobioidei: Sicydiinae). Bull. Fr. Pêche Piscic., 364: 173-185. Watson R.E., Keith P. & Marquet G., 2007. - Akihito vanuatu, a new genus and new species of freshwater goby from the South Pacific (Teleostei: Gobioidei: Sicydiinae). Cybium, Reçu le 5 janvier 2010. 31(4): 341-349. Accepté pour publication le 19 janvier 2010.

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