제주연안에서 흔한가리비, Chlamys nobilis (Reeve)의 종묘생산과 성장

Abstract

이 연구는 제주에 분포하나 자원량이 부족한 흔한가리비, Chlamys nobilis를 일본 오이다현 가리비양식장(Marudo co.)으로부터 이식한 후, 제주연안에서 양식가능성을 시험하기위해 생물학적 특징을 구명하고, 제주연안에서의 흔한가리비 종묘생산 및 양성 기술개발을 위한 제반 기초 연구를 수행하였다.

1. 생식주기 생식소 형태는 초생달 모양이고 생식소가 비대해지면 암컷은 주황색, 수컷은 유백색을 띠어 외관상 암․수 구분이 용이하였다. 조직학적 관찰을 통한 생식소 발달 양상은 암․수 각각 분열증식기, 성장기, 성숙 및 산란기, 휴지기(회복기)의 4단계로 구분할 수 있었고, 일부 자웅동체 개체도 발견되었다. 조직학적 관찰결과 주 산란기는 암․수 모두 5～7월로 관찰되었다.

2. 산란과 유생사육 산란유발방법은 햇빛노출 수온상승자극방법으로 자극 후 40분 이내 100%로 빠르게 반응하였고, 자외선 조사해수자극방법은 70분 이내 100%로 양호하였다. 난 발생 가능수온은 15～30℃ 이었다. 초기 D상 유생에 도달하는 시간은 15, 20, 25 및 30℃에서 각각 63.5, 31.5, 18.5 및 17.0시간이 소요되었다(P＜0.05). 난 발생이 정지하는 생물학적 영도(Biological minimum temperature)는 평균 10.44℃였다. 수온별 유생성장은 수온 24℃시험구에서 각장크기 192.7 ㎛, 생존율 58.8%로 가장 좋았다. 사육밀도별 유생사육은 각장성장 및 생존율이 1개체/mL구에서 183.4㎛, 36.7%와 2개체/mL구에서는, 175.6㎛, 37.2%로 양호하여 흔한가리비 적정 사육밀도는 2개체/mL 이하로 나타났다(P＜0.05). 먹이생물 종류에 따른 유생 성장은 Chaetoceros. calcitrans, Isochrysis. galbana, Pavlova lutheri를 단독 급이한 시험구와 3종을 혼합 공급하였을 때 시험 종료 후의 각장의 성장은 3종 혼합구가 196.7 ㎛로 가장 높았고, P. lutheri 시험구가 174.6 ㎛로 가장 저조하였다(P＜0.05).

3. 부착자패 및 치패성장 부착기의 종류별 부착률은 염화비닐판 수평 설치구에서 가장 좋았고, 차광망, 양파망, 염화비닐판 수직설치 순이었다(P<0.05). 부착 후 60일째까지의 경과일수(X)에 따른 자패의 각장(SL) 성장은 SL = 0.1664e0.0579x(r2 = 0.924) 회귀직선식으로 나타낼수 있었다. 지귀도에서 사육한 각장 1 mm 치패는 1개월후에 4.1±0.8 mm로 성장하였고 2, 3, 4 및 5개월째에는 각각 각장 13.0±1.9, 23.1±3.1, 30.3±4.3, 33.6±5.2 mm로 성장 하였다.

4. 중간양성 가. 양성장 환경 시험 양성장의 표층수온은 위미리 지귀도 연안이 연중 13.6～25.9℃ 범위였고, 옹포리 연안은 12.8～26.7℃ 범위였으며, 표층 염분은 2개소에서 29.6～34.5psu 범위였다. 계절별 표층 및 저층 용존산소는 지귀도 연안에서 6.38～10.91 mL/L와 6.24～8.36 mL/L였다. 조사지역 2개소의 Chlorophyll-a 농도는 지귀도 연안에서 1.05～4.61 ㎍-at/L 범위였고, 옹포리 연안은 0.21～1.34 ㎍-at/L 범위였다.

나. 중간양성 1) 수심에 따른 성장 지귀도 연안에서 390일 동안 수심 5, 10, 15, 20 m에서 양성한 치패의 평균 각장성장은 시험 종료 시 각각 76.7±7.7, 73.3±7.3, 69.4±8.4, 68.7±8.5mm였다. 일간각장성장량은 수심별로 각각 165.6, 154.0 140.0, 137.4 ㎛/day 순으로 수심이 깊어질수록 성장량은 낮았다(P＜0.05).

2) 밀도에 따른 성장 사육밀도별로 10, 20, 40, 80마리/cage를 수용하여 지귀도 연안에서 390일간 양성한 치패의 평균 각장은 각각 77.5±9.8, 71.0±13.0, 63.0±8.1, 59.8±7.5 mm 순으로 성장하였고, 각장의 일간성장량에서도 각각 168.3, 145.8, 115.2, 101.8㎛/day로 사육밀도가 높을수록 성장은 느렸다(P＜0.05). 동일한 밀도 조건으로 옹포연안에서 196일 동안 사육한 결과는 각각 63.8±6.5, 62.1±7.0, 60.0±6.0, 58.5±7.0 mm로 밀도가 높을수록 성장이 느렸다(P>0.05). 흔한가리비의 치패 및 성패에 대한 각고(SH)와 각장(SL)의 상대성장식은 SL = 0.9982H - 2.8326이었고, 각고(SH)와 전중(TW)의 상대성장식은 TW = 0.4 × 10-3SH2.8153였다.

다. 수온 및 염분 내성 수온 28, 30, 32℃에 대한 고수온내성시험 결과, 수온 28℃에서는 시험기간 20일 동안 13.3% 폐사하였고, 수온 30, 32℃에서 50% 폐사 시간은 각각 96시간, 36시간으로 나타났다. 저수온내성 시험 결과, 수온 7℃에서는 36시간 만에, 10℃에서는 168시간에 50% 폐사하였고 수온 13℃에서는 시험기간(10일) 동안 폐사 개체가 없었다. 염분내성 시험결과는 수온 15℃에서 염분 28 psu에서는 시험 종료 시까지(354시간) 30%가 폐사하였다. 염분 26, 24, 22, 20 및 18psu 에서는 각각 261시간, 222시간, 126시간, 45시간 및 42시간 만에 50%가 폐사하였다. 수온 20℃에서 염분 28psu에서는 315시간 동안 6.7%의 폐사를 나타냈고, 26, 24, 22, 20, 18 psu에서는 각각 315시간, 189시간, 141시간, 33시간 및 12시간에 50% 폐사 하였다. 수온 25℃에서는 28 psu에서도 339시간에 50%가 폐사하였고, 26, 24, 22, 20, 18psu에서는 각각 246시간, 156시간, 120시간, 30시간 및 5시간에 50%가 폐사하였다.

Noble scallop, Chlamys nobilis, is distributed off the temperate and subtropical coasts including Jeju island, Korea. The scallop is famous for various shell colors in early life stage. Even the scallop has known inhabiting in Jeju coast, the population is very rare. To investigate its possible aquaculture in Jeju coast, larval and adult C. nobilis was imported from Oita Prefecture of Japan in 2001, and performed serial experiments on inducing spawning, larval rearing, and outdoor cultivation in relation to different conditions.

1. Reproductive cycle The matured scallop gonads were slender and convex like a waxing crescent phase of the moon in common, but differed in color: reddish for female and milky for male. Microscopic observation of the gonad tissue confirmed that most of the scallop were dioecious with 4 distinctive stages: multiplication stage, growing stage, mature and spent stage, recovery stage (resting stage), while some were hermaphrodite. Main spawning season were esteemed between May and July.

2. Spawning induction and larval culture Four spawning stimulations were applied for spawning induction. Most effective method was exposure method with sunlight as 100% induction rate in 40 minutes, and followed by the U.V. irradiation method as 100% induction rate in 70 minutes. The working water temperatures for spawning were 15～30℃ (P＜0.05). The time to the first D-shape larvae were strongly dependent on water temperature. They were 63.5, 31.5, 18.5 and 17.0 hours for 15, 20, 25 and 30℃ experiments, respectively. The biological minimum temperature for reproduction was 10.44℃ on average. To find the suitable environmental conditions, D-shape larvae were tested for 12 days. The best water temperature for larval culture was 24℃ in which the larval survival was 58.8% at the size of 192.7 ㎛. Better growth was achieved at larval culture densities less than 2 inds/mL (P＜0.05). The growth and survival were 183.4 ㎛ and 36.7% for 1 ind/mL experiment and 175.6 ㎛ and 37.2%2 for inds/mL experiment, respectively. The scallop larvae fed on combined foods (Chaetoceros. calcitrans, Isochrysis. galbana, and Pavlova lutheri) gained better growth over those fed single food (Pavlova lutheri) (P＜0.05). Larval size fed combined foods was 196.7 ㎛, while the larvae fed single food was 174.6 ㎛ at the end of the experiment.

3. Larval attachment and spat growth The larval attachment rates were dependent on the substrates with the best result in horizontally-settled polyvinyl plate, followed by light shading screen, onion bag, and polyvinyl plate vertical. The spat growth after the attachment was expressed as the equation of SL = 0.1664e0.0579D(r2 = 0.924), where SL is shell length and D is day after the attachment. The spat grew to 4.1, 13.0, 23.1, 30.3, and 33.6 mm in 1, 2, 3, 4, and 5 months after installation in the nursery ground, respectively.

4. Nursery growth 4-1. Environmental parameters of the nursery ground The water temperature of two nursery grounds were 13.6～25.9℃ for Jigwido and 12.8～26.7℃ for Ongpo with lowest in February and highest in August. The salinities of the surface water for both locations were 29.6～34.5 psu with lowest in February and highest in August. The variations in dissolved oxygen for surface and bottom water masses were 6.38～10.91 mL/L and 6.24～8.36 mL/L with the highest in February and lowest in November. The levels of chlorophyll a for Jigwido and Ongpo were 1.05～4.61 ㎍-at/L and 0.21～1.34 ㎍-at/L, respectively.

4-2. Nursery growth 1) Spat growth by depth The spats at Jigwido nursery ground gained shell lengths of 76.7±7.7, 73.3±7.3, 69.4±8.4, and 68.7±8.5 mm by depths of 5, 10, 15, and 20 m for 390 days cultivation, respectively. The daily gains of the shell length for each depth were 165.6, 154.0 140.0, and 137.4 ㎛/day (P＜0.05). 2) Spat growth by density The spats at Jigwido nursery ground gained shell lengths of 77.5±9.8, 71.0±13.0, 63.0±8.1, and 59.8±7.5 mm by densities of 10, 20, 40, 80 inds/cage for 390 days cultivation, respectively. The daily gains of the shell length for each density were 168.3, 145.8, 115.2, and 101.8 ㎛/day (P＜0.05). The spats at Ongpo nursery ground gained 63.8±6.5, 62.1±7.0, 60.0±6.0 mm in shell lengths by the same culture densities for 196 days cultivation. These density-dependent spat growth was similar to those at Jigwido nursery ground. The relative growth of the spats in the nursery ground were: SL = 0.9982SH - 2.8326, and TW = 0.4 × 10-3SH2.8153, where, SL is shell length, SH is shell height, and TW is total weight.

4-3. Spat tolerance to water temperature and salinity When the spats were exposed to high water temperatures of 28, 30, and 32℃ for 20 days, they had shown 13.3% mortality at 28℃ condition for the period. And the lethal temperature 50s were calculated as 96 hours at 30℃ and 36 hours at 32℃. While the spats were exposed to low water temperature of 7, 10, and 13℃, the lethal temperature 50s were shown 36 hours and 168 hours at 7 and 10℃, respectively. But no mortality was observed at 13℃ condition for 10 days. When the spats were exposed to various salinities at 15℃ condition for two weeks, the mortality at 28 psu was shown as 30%. The lethal salinity 50s were 261, 222, 126, 45, and 42 hours at 26, 24, 22, 20, and 18 psu conditions. In salinity tolerance test at 20℃ condition, the lethal salinity 50s were 315, 189, 141, 33, and 12 hours at the condition of 26, 24, 22, 20, and 18 psu, respectively. But the spats exposed to 28 psu had shown only 6.7% mortality. In salinity tolerance test at 25℃ condition (highest in this salinity tolerance test), the lethal salinity 50s were 246, 156, 120, 30, and 5 hours at 26, 24, 22, 20, and 18 psu conditions, respectively. But, the spats exposed to 28 psu at 25℃ had shown only 6.7% mortality for two weeks.