Aquaculture Sci. 58（1），55－63（2010）

Transplantation of the Loxechinus albus in Chiloé Island, Chile

Sohei KINO

Abstract: In order to understand methods to effectively utilize the resource of the Chilean sea urchin, Loxechinus albus, a transplantation experiment was carried out during 6 months from August 1988 to February 1989 in Chiloé Island, Chile. One thousand adults at 58.6 mm in mean test diam- eter showing mal-developed gonads in Linao which was depauperate in algae were transplanted to an experimental area of 400 m2 in Hueihue which was rich in algae. The gonad index improved from 8.5 to 13.7 two months after transplantation. The recovery rate of transplanted L. albus after 6 months was 83.0% (90.4% including sampled individuals). The movement range of this species was very narrow. In Linao, L. albus barely gathered to algae put in a net bag; the numbers that gathered were 2, 10, 15, and 20 individuals in 4, 8, 15, and 21 days after providing algae, respectively.

Key words: Loxechinus albus; Transplantation; Gonadal improvement; Movement

Some countermeasures have been taken for releasing (Stotz et al. 1992), and culture (Bückle the propagation of sea urchins, such as artificial et al. 1977a, 1977b); however, there is no study bank creation, transplantation, and the release on transplantation. Although Chiloé Island of juveniles through seed production. Among was one of the main fishing banks of L. albus them, transplantation is used to enhance the (Barahona et al. 2003; Stotz 2004), there were commercial value of sea urchin gonads. In some places where L. albus showed mal-devel- Japan, the transplantation of sea urchins to other oped gonads. These sea urchins were not tar- waters for the quantitative improvement of the geted of the catch in the eastern coastal waters gonad has been implemented for Anthocidaris of Chiloé Island. In this study, a transplanta- crassispina (Nakamura and Yoshinaga 1962), tion experiment involving L. albus showing Strongylocentrotus intermedius (Kawamura 1965; mal-developed gonads was carried out in the Tomita et al. 1986), and S. nudus (Kawamura eastern coastal waters of Chiloé Island to inves- 1963; Akimoto 1976; Yoshida and Ebina tigate its utility and effectiveness. Additionally, 1998). Additionally, the transplantation of movement related to the recapturing of trans- Hemicentrotus pulcherrimus yielded favorable planted sea urchins was discussed. results in an artificially created bank involving the installation of rocks (Taki and Higashida Materials and Methods 1964). Also, in the Mediterranean, the trans- plantation of Paracentrotus lividus led to favor- Sea urchins able gonadal improvement (San Martin 2004). Figure 1 shows the experimental sites. At the In the Chilean sea urchin Loxechinus albus, collection site in Linao, numerous L. albus were studies on propagation are available, such present. Algae as a source of food for them as on seed production (Guisado and Castilla were scarce. The sea bottom was a rock bed, 1987; Zamora and Stotz 1994; Cárcamo 2004), and the accumulation of sand or non-geniculate

Received September 16, 2009: Accepted December 4, 2009. INTEM Consulting Inc., Nishi-shinjuku, Shinjuku-ku, Tokyo 160-0023, Japan. ＊Corresponding author: E-mail: [email protected] (S. Kino). 56 S. Kino

calculated based on individuals removed from the quadrat (400 m2) was <0.1 individuals/m2.

Hueihue Linao Secondly, the density of L-La was investigated by 10 random samplings using a 1-m square frame, and calculated as 19.4 individuals/m2. Then L-La were collected on August 10 in Linao. One thousand individuals of 58.6 mm in mean test diameter (mean body weight: 72.9 g) were collected in 30 minutes by scuba diving employ- ing 2 divers. Collected L-La were put in two Fig. 1. Transplantation experiment sites for Loxechinus albus in eastern coastal waters of Chiloé Island. ●: collec- 100-liter polycarbonate tanks covered with wet tion site of L-La (native L. albus in Linao), ○: transplanta- newspaper without adding any seawater, and tion site in Hueihue. were transported to Hueihue by boat. Finally, L-La were released together within an area of was also noted in some places. 1 x 2 m at the center of the quadrat by a diver. Here, L. albus, ranging on the rock bed or field The conditions at the time of transplantation of non-geniculate coralline algae, showed mal- were as follows: collected L-La were kept in air developed gonads, their test could be easily cut for 21–38 minutes untill release, the air tem- with scissors, they showed fine spines, weak perature was 10.0 °C, the seawater temperature adherence, and had an overall body color of was 10.7 °C in Linao and 10.8 °C in Hueihue, darkish red. Sea urchins with mal-developed the weather was cloudy, and there was no wind. gonads were also distributed in Teupa or Yaldad The experiment lasted until February 10, 1989 in the southern part of Chiloé Island (Kino and for 6 months. Agatsuma 2007), where algae hardly grew and drift algae were not found, or in places where Measurement and observation tidal drift was poor and mud segmentation The following investigations were carried out occurred, even if there were algae. during the transplantation experiment: On the other hand, at the transplantation Oceanographic observation: The seawater site in Hueihue, few L. albus and abundant temperature and salinity at the surface (0 m) algae were found. The sea bottom type was in Hueihue were measured weekly using an big stones or pebbles, and sand accumula- electronic thermo-salinometer (KENT/EIL tion was present in some parts. Here, L. albus 5005). had well-developed gonads, a thick test, thick Gonad index (GI): Thirty individuals of L-La spines, showed strong adherence, and had an were measured every month in Linao for 7 overall body color of bright red. months, and every 2 months for T-La for a Hereinafter, L. albus is defined as follows: total of 6 months. The test diameter, body L-La: L. albus with mal-developed gonads in weight, and gonad weight of every speci- Linao (indigenous to Linao) men were measured using a varnier caliper H-La: L. albus with well-developed gonads in and an electronic balance with an accuarcy Hueihue (indigenous to Hueihue) of 0.1 mm and 0.1 g, respectively. The gonad T-La: L-La transplanted to Hueihue index was calculated by (Gonad weight/Body Firstly, before carrying out transplantation, weight) x 100. a 20-m square quadrat made with 10-mm diam- Algal standing crop: Algae were collected eter rope and 40-kg sand bags set at the corners every month within a 1 m2 area nearby the was placed on the sea bottom at a 5-m depth collection and transplantation sites in Linao for on August 8, 1988 in Hueihue. Then, all H-La 7 months and Hueihue for 6 months, respec- (10 individuals) were removed from inside the tively, and the wet weight (g wet wt/m2) was quadrat by scuba diving. The density of H-La calculated. Transplantation of Loxechinus albus 57

Recovery number: All T-La in and around of L-La and T-La, and the change in the algal the transplantation quadrat were recovered standing crop in Linao nearby the collection by scuba diving, and then counted 6 months point of L-La, and in Hueihue nearby the trans- after transplantation. plantation quadrat. Although the initial GI of Movement: Movement of T-La was observed T-La was 8.5 in August, it increased to 13.7 two in the quadrat in Hueihue, and the aggrega- months after transplantation in Hueihue. The GI tion behavior of L-La was observed in Linao change due to transplantation was prominent; on placing Ulva sp. and however, at and after 4 months (December), in a net bag taking photos with a waterproof the GI ranged around 10. The GI of T-La was camera (Nikonos V, UW-Nikkor 20 mm/F2.8, always greater than that of L-La during this and Nikonos speed-light SB-103) after 1, 2, 4, experiment. The GI of L-La was always <9 from 8, 15, 21, and 35 days. Additionally, near the August to January, while a small increase was site of observing aggregation behavior, the observed from February–March, synchronized approximate distance moved by a specific with the growth of algae in Linao. individual with characteristic white spine tips The algal standing crop in Hueihue was abun- was also measured at the time of the diving dant in August and September, when only Ulva above-mentioned by tracing for one month sp. was found. Especially, in September, its without touching it. quantity was 1534 g wet wt/m2. However, they were washed away due to poor weather condi- Results tions in October. Consequently, the standing crop decreased to 63 g wet wt /m2. Then, Ulva Gonad index and algal standing crop sp. grew gradually, with the quantity reach- Figure 2 shows the seawater temperature ing the same level as in August to December, and salinity change at the surface (0 m) during at approximately 800 g wet wt /m2. It did not the transplantation experiment in Hueihue. disappear until February. On the other hand, The seawater temperature increased gradu- in Linao, only dimensionless algal growth ally, ranging between 10.4 and 15.5 °C, and the salinity ranged between 32.2 and 34.2 with small fluctuations. Figure 3 shows the GI change 15.0 T-La (Hueihue) L-La (Linao)

35 10.0 34 Gonad index 33

32 5.0

16 ) 2 1600 Hueihue C Salinity Linao 1200 14 800

12 400

Algal standing crop (g/m 0 * Seawater temperature ° 10 Aug Sep Oct Nov Dec Jan Feb Mar Aug Sep Oct Nov Dec Jan Feb '88 '89 '88 '89 Fig. 3. Changes in the gonad indices of L-La (native Fig. 2. Changes in the seawater temperature and salinity Loxechinus albus in Linao) and T-La (transplanted L. albus at the surface (0 m) in Hueihue during the transplantation to Hueihue), and alteration in the algal standing crop in experiment. Linao and Hueihue. Asterisk: no data in Hueihue. 58 S. Kino

Table 1. Summary of the transplantation experiment for Loxechinus albus in the 400 m2 transplantation quadrat in Hueihue from August 1988 to February 1989 (H-La: native L. albus in Hueihue, L-La: native L. albus in Linao, T-La: transplanted L. albus to Hueihue) 1988 1989 Aug Oct Dec Feb Total Removed number of H-La from the quadrat (20x20 m) 10 5 15 Transplanted number (L-La, TD 58.6 mm, BW 72.9 g) 1000 1000 Sampled number of T-La for measurement 40 34 74 Recaptured number of T-La 830 830 (inside the quadrat within a 5-m radius from the center) (796) (the remainder of the quadrat, >5 m from the center) (15) (outside the quadrat at a 5-m distance) (19) Number of dead T-La ＊1 1 ＊found at the center of the quadrat. was found from August to November. After Movement December, Ulva sp. and M. pyrifera showed Movement of L. albus was observed both new growth, and after January, the algal stand- in Hueihue and Linao. Six months after trans- ing crop in Linao reached the same level as in plantation in Hueihue, out of 830 individuals Hueihue, with approximately 300 and 500 g wet recaptured, 796 (96%) remained within a 5-m wt /m2 in January and February, respectively. radius from the center of the quadrat. Another Drift algae were not observed between August 15 individuals moved between 5 and 10 m, and and November in Linao. the remaining 19 individuals were outside the quadrat, moving 15 m from the center of the Recovery number quadrat. Figure 4 shows the aggregation of L-La Table 1 summarizes the transplantation experi- in Linao. The numbers of individuals that aggre- ment. A total of 830 individuals of T-La were gated toward the algae in the net bag were 0, 1, recaptured; its breakdown was 796 individuals 2, 10, 15, 20, and 20 in 1, 2, 4, 8, 15, 21, and 35 (inside the quadrat within a 5-m radius from the days, respectively. Although many L. albus were center), 15 individuals (the remainder of the observed around the net bag in the figure, the quadrat), and 19 individuals outside the quadrat number of individuals that aggregated toward (a 5-m distance from the quadrat). One dead the algae in the net bag was low at one month. individual was found at the center of the quad- Moreover, it was observed that L. albus around rat, and 5 individuals of local H-La were found the net bag also moved inch by inch. One L. in the quadrat. No broken sea urchin tests, indi- albus that showed the distinct characteristic of cating possible predation, were found. Since 40 white-colored spine tips in Linao moved only and 34 individuals were sampled for measure- 1.6 m in one month. ment in October and December, respectively, the recovery rate was calculated as 83.0% (90.4% Discussion including sampled individuals). T-La showed no change in their external morphology and they Gonad index and algal standing crop were easy to distinguish from H-La due to their In this study, L. albus with mal-developed body color, spine color, and fragility of the test. gonads were collected in Linao, an urchin Additionally, T-La showed a stronger adherence barren, and then transplanted to Hueihue, with than L-La, as more force was needed to remove abundant algae, to investigate whether they them from stones or rocks compared with L-La. would show gonadal enhancement. The GI of L-La barely increased, remaining below 10 at all times, however, that of T-La increased to 13.7 Transplantation of Loxechinus albus 59

(1.6 times the initial GI) two months after trans- plantation in October in Hueihue. The average GI in October 1986 in Hueihue was 13.8 (Kino and Agatsuma 2007), suggesting that the GI of T-La reached the average value in Hueihue in this period. Additionally, as no drift algae were observed between August and November in Linao, the GI of L-La did not increase. In the period of August–December, there was a marked difference in the algal standing crop between Linao and Hueihue (Fig. 3), and algal abundance was involved in gonadal develop- ment over a short period. Transplanted S. intermedius, in 2 months, show a rate of gonadal development more than 5 times that of un-transplanted ones from the end of April (Kawamura 1965). Equally, transplanted S. nudus show GI improvement from 4.43 to 12.16 in 5 months (Yoshida and Ebina 1998) and from 4.3 to 15.2 in 2 months (Kawamura 1963). Transplanted Paracentrotus lividus of 30–50 mm in test diameter show a sig- nificant improvement in the GI from 1.12 to 4.12 six months after transplantation (San Martin 2004). On the other hand, the GI of S. nudus from trophically poor coralline flats increases from 6.5 to 13.4 in 20 days and to 17.5 in 2 months by rearing with excess (Laminaria religiosa), reaching the minimum level for com- mercial landing (Agatsuma 1999). However, in Linao, although algae began to grow in December and sufficient algae were found in February and March, the GI increase was very small. This suggested that the algal standing crop did not always reflect the increase in the GI, because this period coincided with the mini- mum GI period after the spawning season (Kino and Agatsuma 2007). Agatsuma (1999) also commented that it is preferable to transplant S. nudus 2 months before maturation and the spawning season. Therefore, the GI of T-La also did not increase after December and showed almost the same value as that of L-La. In other words, if it is necessary to perform effective transplantation in a short time, it should be implemented a few months before the maxi- Fig. 4. Aggregation of Loxechinus albus around Ulva sp. and Macrocysis pyrifera in a net bag in Linao. The number mum GI period (just before spawning). If trans- plates show the days after positioning the net bag. plantation is carried out after the spawning 60 S. Kino season, it is likely that it will take about 1 year (Fig. 2), predation may occur. As for preda- before having commercial value. Although it is tors of L. albus, brachyurans and asteroid have thought that transplantation markedly stresses been reported in Chiloé Island waters (Kino sea urchins due to their collection and trans- 2009); however, evidence of predation such as port, considering these unfavorable conditions, the presence of broken tests was not found in this period in August (austral winter) seemed the transplantation quadrat except for one dead advantageous because it was low-temperature individual. Thus, it is thought that a low risk season (Fig. 2). of predation is one of the reasons for the high The GI of T-La increased to 13.7 in October, recovery rate. Another reason is their locomo- and then it decreased to 10.3 in December. tory behavior. In kelp forests, Strongylocentrotus Although this period coincided with the - franciscanus hardly moves compared with indi- ing season of this species in Hueihue (Kino and viduals outside the forest depending on the Agatsuma 2007), the spawning of T-La was not presence of food (Mattison et al. 1977), and the confirmed. Assuming that they spawned, this movement of S. droebachiensis increases after means that the spawning population increased reaching >15 mm in test diameter (Dumont et al. as a result of the transplantation of L. albus 2004). A difference is found in their locomotory which showed no capacity to spawn; transplan- behavior depending on the environment around tation is also useful as one of the propagation them, size, or species. The movement range of methods for this species. L. albus is narrow, and individuals do not forage It is necessary to understand the algal far for food (Dayton 1985). Some results of this requirements of sea urchins on actual transplan- study also support this. T-La hardly moved from tation; however, the algal consumption of T-La the point of release, and 80% of them remained was not investigated in this study. At sizes of 70 within a 5-m radius of the release point after and 40 mm in test diameter, L. albus consumes 6 months. Although the maximum moving 230 g/month of M. pyrifera and 38 g/month distance was 15 m in that period, individuals of Lessonia nigrescens, respectively (Bückle that moved this distance totaled less than 2% of et al. 1977b). The body weights are ca. 160 g T-La. Transplanted S. nudus hardly moves after (70 mm) and ca. 30 g (40 mm), respectively 166 days (Akimoto 1976), or moves approxi- (Bückle et al. 1977a), and the daily rate of algal mately 20 m in 2 weeks (Kawamura 1963). consumption can be calculated as 4.8 and 4.2% Transplanted S. intermedius also hardy moves; of the body weight, respectively. Consequently, however, some individuals move more than the algal standing crop in an area transplanted 70 m (Kawamura 1965). In the case of released into should be more than 5% of the total weight juvenile S. intermedius (20 mm in test diameter), of sea urchins transplanted every day. Algal it moves approximately 20 m from the release growth or algal supply as drift algae should be point if seeded in an adequate place (Monma et greater than the amount grazed by sea urchins. al. 1992). In this study, it was confirmed that the distance moved by one L. albus was 1.6 m in one Recovery and movement month in Linao. Individuals hardly moved for Numbers of transplanted P. lividus of 30– foraging; only 20 individuals gathered around 50 mm in test diameter decrease by 7.7% (mainly algae put on the sea bottom in one month. In predation by fish) after about 1 month, and coralline flats like Linao, it is suggested that low their recovery rate is 60% after 6 months (San energy caused by a lack of food further reduces Martin 2004). The recovery rate of transplanted movement. On the other hand, however, S. L. albus (58.6 mm in mean test diameter) in nudus, in coralline flats gather in a short period this study was high, at more than 80% (90.4% around brown algae (L. religiosa) put on a rocky including sampled individuals) after 6 months. sea bottom in south-west Hokkaido, Japan; Since the activity of predators rises due to the approximately 200 individuals gather after gradual increase in the seawater temperature 24 hours (Fujita 1987). Consequently, it can be Transplantation of Loxechinus albus 61 concluded that confined locomotory behavior is urchins, and algal standing crop including drift a characteristic of L. albus. algae. However, sites influenced by freshwater are inappropriate for transplantation even if Condition of transplantation there are abundant algae, because mass mor- A negative correlation is noted between algal tality occurs (Kawamura 1965). Although the quantities and the density of sea urchins such transplantation site salinity was stable during as Evechinus chloroticus (Ayling 1981), L. albus the experiment showing favorable conditions in (Dayton 1985), S. nudus (Agatsuma et al. 1997), this study, we should also pay attention to envi- S. intermedius on juvenile release (Sakai et al. ronmental factors other than algal food. 2004), and Heliocidaris erythrogramma (Valentine As a candidate transplantation site, a former and Johnson 2005). The state of the sea bottom bank of L. albus is better, because it will have a grazed by sea urchins is called“ Coralline flat” sufficient provision of algae and is an adequate (Ayling 1981), “Urchin barren” (Coyer et al. natural habitat for this species. Banks were 1993),“ Isoyake” (Fuji 1999), and so on. It is reported in which the density of L. albus was believed that the heavy grazing of algae by sea more than 20 individuals/m2 (Piedra Lile, urchins is one of the triggers of algal disappear- Chiloé Island, X region) and more than 60 ance. In fact, it was proven that coralline flats are individuals/m2 (Canal Leucayec, Guaitecas, XI maintained by high-level foraging activity of the region) (Barahona et al. 2003). In Laitec (Chiloé Japanese sea urchin S. nudus on the Japan sea Island, X region), where L. albus distributed in coast of Hokkaido (Agatsuma et al. 1997). groups like patches on the pebble sea bottom, Many coralline flat areas were seen in east- a density above 80 individuals/m2 in each ern coastal waters of Chiloé Island, and the patch of L. albus was observed (Kino 2009). sea bottom comprised pebbles covered with Consequently, it is suggested that L. albus can non-geniculate coralline algae (Kino 2009); be transplanted at a high density considering Linao was an urchin barren zone showing a the algal standing crop and environment of high density of sea urchins and absence of these sites where banks had previously formed. algal growth. However, even L. albus in a zone Recently, the fishery of L. albus shifted fur- where no algae grew showed well-developed ther south of Chiloé Island, as the darkish- gonads in many cases. This means that L. albus colored gonads of bigger individuals has been utilizes drift algae; the intestine was filled with associated with poor quality (Barahona et al. algae even when no algae grew around them. 2003). A difference in the gonad color (yellow– Consequently, in coralline flats, it is impossible brown) depending on the habitat has reported for the gonads to develop unless drift algae for A. crassispina (Yasuda et al. 1982). In both exist. Thus, in coralline flats with the absence S. intermedius and S. nudus, individuals inhabit- of drift algae such as Linao, L. albus shows mal- ing a deeper sea bottom show mal-developed developed gonads throughout the year. In this gonads because of a lack of algae (Osaki and study, the GI of L. albus with mal-developed Kawamata 1991). Additionally, S. nudus ranging gonads clearly improved on increasing the at deeper sites (>15 m) shows mal-developed algal standing crop, but, as aforementioned, and dark-colored gonads commercially selected when sea urchins move little to forage for algae against, showing a correlation between the despite the existence of algal growth, or drift GI and quantity of brown algae (Kirihara and algae are not available, gonadal development Yamauchi 2004). Although the gonadal qual- is poor. The daily rate of algal consumption of ity was not investigated in this study, since the L. albus was ca. 5%, as previously mentioned. gonad color has a relationship with food, age, Therefore, in the case of carrying out an actual and the natural habitat (Matsui 1966), we need transplantation, this behavior should be consid- to explore transplantation methods to increase ered, and it is necessary to discuss the extent the commercial yield of L. albus. On the other of the transplantation area, total weight of sea hand, S. intermedius shows a non-synchronized 62 S. Kino reproductive cycle when the transplantation of flats and fed excess kelp, Laminaria religiosa. adults and release of juveniles are carried out in Suisanzoshoku, 47, 325-330. Agatsuma, Y., K. Kawamata and S. Motoya (1994) geographically separated areas differing from Reproductive cycle of cultured seeds of the sea their original habitat (Tomita et al. 1986), and urchin, Strongylocentrotus intermedius produced from geographically separated population. Suisanzoshoku, from their spawners’ habitat (Agatsuma et al. 42, 63-70 (in Japanese). 1994), respectively. Therefore, for the propaga- Agatsuma, Y., K. Matsuyama, A. Tanaka, T. Kawai and N. tion of resources, transplantation sites should Nishikawa (1997) Marine algal succession on coral- line flats after removal of sea urchins in Suttu Bay on also be determined considering this phenom- the Japanese Sea coast of Hokkaido, Japan. Nippon enon of change in the reproductive cycle. Suisan Gakkaishi, 63, 672-680 (in Japanese). Akimoto, Y. (1976) Transplantation of Strongylocentrotus nudus in Fukushima Prefecture. Suisanzoshoku, 23, In this study, the effectiveness and possibility 149-154 (in Japanese). of L. albus transplantation were shown. Since Ayling, A. M. (1981) The role of biological disturbance in the transplantation experiment was carried out temperate subtidal encrusting communities. Ecology, 62, 830-847. only from August to February for 6 months, Barahona, N., J. Orenzans, A. Parma, G. Jerez, C. Romero, and the other months were not targeted, the H. Mirand, A. Zuleta, V. Cataste and P. Galvez (2003) Bases biológicas para rotación de áreas en el recurso time period after transportation was short, and erizo. Informe final, Fondo Investigación Pesquera number transplanted was also small. The mini- PIN No.2000-18, Instituto de Fomento Pesquero, mum fishing legal size is 70 mm in test diam- Investigación y Fomento Pesquero, 378 pp. Bückle, F., C. Guisado, C. Serrano, L. Córdoba, L. Peña eter (Stotz 2004), and a few years are needed and E. Vásquez (1977a) Estudio de crecimiento en before recapturing when small individuals are cautiverio del erizo Loxechinus albus (Molina) en las transplanted. Consequently, it is necessary costas de Valparaíso y Chiloé, Chile. Anales del Centro de Ciencias del Mar y Limnología. Universidad to obtain more information on the adequate Autónoma de México, 4, 141-152. size, period, and method for actual mass trans- Bückle, F., C. Guisado, C. Serrano and E. Vásquez (1977b) portation. Rogers-Bennett (2007) commented Estudio de la alimentación en cautiverio del erizo Loxechinus albus (Molina) en las costas de Valparaíso that transplantation may be more effective for y Chiloé, Chile. Anales del Centro de Ciencias del Mar gonadal enhancement than artificial seed pro- y Limnología. Universidad Autónoma de México, 4, 153-160. duction. Further studies are needed to investi- Cárcamo, P. (2004) Massive production of larvae and seeds gate not only the improvement of gonad size but of the sea urchin Loxechinus albus. In“ Sea urchins. also the quality from the viewpoints of resource Fisheries and Ecology” (ed. by J. M. Lawrence and O. Guzmán). DEStech publ., Lancaster. pp. 299-306. propagation and fishery of this species. Coyer, J. A., R. Ambrose, J. Engle and J. Carroll (1993) Interactions between corals and algae on a temperate Acknowledgements zone rocky reef: mediation by sea urchin. J. Exp. Mar. Biol. Ecol., 167, 21-37. Dayton, P. K. (1985) The structure and regulation of some This study is a part of the international techni- south American kelp communities. Ecol. Monogr., 55, cal cooperation of Overseas Fishery Cooperation 447-468. Dumont, C., J. H. Himmelman and M. P. Russell (2004) Foundation between Japan and Republic of Chile. Size-specific movement of green sea urchins I sincerely thank Dr. H. Nakagawa of Hiroshima Strongylocentrotus droebachiensis on urchin barrens in eastern Canada. Mar. Ecol. Prog. Ser., 276, 93-101. University and Dr. Y. Agatsuma of Tohoku Fuji, A. (1999) Advances in ecological studies of“ Isoyake”. University for their kind comments and sug- In“ The ecological mechanism of ‘Isoyake’ and marine gestions for the preparation of this manuscript. afforestation” (ed. by K. Taniguchi). Koseisha Koseikaku-120, pp. 9-24 (in Japanese). I am also grateful to Dr. K. Kawamura for his Fujita, D. (1987) Chained kelp method for feeding sea guidance and encouragement and Mr. Ricardo urchin (preliminary report). Suisanzoshoku, 35, 139-141 Troncoso T. for supporting the study. (in Japanese). Guisado, C. and J. Castilla (1987) Historia de vida, reproducción y avances en el cultivo del erizo comes- References tible chileno L. albus (Molina, 1782) (Echinoidea; Echinidae). In“ Manejo y Desarrollo pesquero” (ed. by P. Arana), pp. 59-68. Agatsuma, Y. (1999) Gonadal growth of the sea urchin, Kawamura, K. (1963) Transplantation test of Strongylocentrotus Strongylocentrotus nudus, from trophically poor coralline nudus in Iwanai. Hokusuishi-Geppo, 20, 20-27 (in Transplantation of Loxechinus albus 63

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チリ共和国チロエ島におけるチリウニ Loxechinus albus の移植

城野草平

チリウニ Loxechinus albus 資源の有効利用のため，1988年 8 月から1989年 2 月にかけて 6 ヶ月間の 移植試験をチリ共和国チロエ島で実施した。海藻に乏しい Linao に生息する生殖腺の発達が悪いチリ ウニ1000個体（平均殻径58.6 mm）を海藻が豊富な Hueihue に設置した400 m2 の試験区に移植した。 移植後 2 ヶ月で生殖腺指数が8.5から13.7に改善した。移植後 6 ヶ月の回収率は83％（サンプリング個 体を含めれば90.4％）であった。チリウニの移動範囲は狭かった。Linao ではチリウニはネットに収 容した海藻にあまり集まらず，その数は海藻設置 4, 8, 15, 21日後にそれぞれ 2, 10, 15, 20個体であっ た。