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1.
White sharks Carcharodon carcharias aggregate at specific times of the year at localities along the South African coast. At Mossel Bay, on the southern Cape coast, four sites were sampled (Seal Island, Hartenbos, Kleinbrak and Grootbrak) to investigate spatial and seasonal patterns in relative abundance and life-history composition. These are known aggregation sites within the bay, each having particular physical and/or biological characteristics. Sightings-per-unit-effort data were collected from February to December 2008–2010. Sighting rates demonstrated significant seasonal and interannual variation at the four sites. The highest mean sighting rate was recorded at Seal Island and the lowest at Hartenbos, which might be a consequence of differences in prey availability. The greatest interannual variability was recorded at Kleinbrak, followed by Seal Island, with little variability at Grootbrak and Hartenbos. White sharks appeared to concentrate at Grootbrak and Kleinbrak in summer and autumn, at Seal Island in winter, and at Hartenbos and Seal Island in spring. All life-history stages were present year-round but their occurrence was influenced significantly by season (p < 0.05), although not site. Few adults (325–424 cm total length) were seen, with the highest frequency being in spring, whereas that of young-of-the-year (≤174 cm) was in autumn. Juveniles (175–324 cm) constituted 78% of the animals sighted, indicating that Mossel Bay is an important aggregation site for this life-history stage.  相似文献   

2.
We present the first quantitative study of the occurrence, size and sex of white sharks Carcharodon carcharias at Bird Island, Algoa Bay. Twenty-two boat trips were made to Bird Island between November 2009 and October 2011 to chum for sharks. A total of 53 sharks was observed over the study period, ranging in size from 1.5 to 4.5 m total length (TL) and with the majority (60.3%) being <3 m TL. The sex ratio of sharks for which sex could be determined was not significantly different from unity. In both study years, sharks were present only in the winter between April and November with a maximum of 1.2 sharks sighted per hour. A zero-altered model, comprising a logistic regression to model presence/absence and a log-normal generalised linear model for abundance, showed that season explained the presence of sharks, peaking in mid-July, with abundance being significantly higher with higher barometric pressure. This study identified Bird Island as an important white shark aggregation site on the east coast of South Africa. These data are crucial not only to improve our understanding of white shark seasonal distribution and biology, but also for the long-term management and conservation of the species in South Africa.  相似文献   

3.
The smooth hammerhead shark, Sphyrna zygaena, occurs in warm temperate waters around the northern North Island of New Zealand. Commercial fishing records and research trawl survey data were used to determine their distribution. Highest catch rates were recorded in relatively sheltered bays and coastlines along the northeast coast of North Island. Neonate and juvenile sharks use shallow coastal waters and large harbours and estuaries as nursery areas up to an age of two years and total length of 150?cm. Five sharks were electronically tagged but two apparently died and three (137–160?cm total length) returned useful data. Two tagged sharks remained in or near the Bay of Islands for 6–55 days after tagging, moving extensively through the bay. A third shark moved about 155?km southeast in 250 days. That shark spent 70 days mostly shallower than 10?m (94% of time) with occasional dives to 40?m. Thereafter, it oscillated between the surface and depths of 60?80?m, with most time (55%) being spent at 40?60?m. Maximum recorded depth was 144?m.  相似文献   

4.
Genetic variation and population structure in the New Zealand snapper   总被引：1，自引：1，他引：0  
Fifteen proteins encoded by 23 gene loci were electrophoretically surveyed in two samples of snapper Chrysophrys auratus (Forster) from Wellington Harbour and the Hauraki Gulf. Between 17% and 26% of the loci examined were found to be polymorphic and the proportion of heterozygous loci per individual was 7.9% to 8.4%. Using Rogers’ genetic distance coefficient an overall similarity of 0.98 was calculated between the two samples.

Three polymorphic loci Est‐4, Gpi‐1, and Idh were examined in an additional 10 samples from around New Zealand. Two genetically distinct stocks were apparent: one along the west coast, the other along the east coast of the North Island. There was an indication of stock mixing at Ninety Mile Beach and in the Bay of Plenty and East Cape. The distribution of alleles at the Est‐4 locus revealed a third stock in Hawke Bay that is genetically more similar to the west coast than the east coast stock. Hydrological conditions in Hawke Bay are more similar to those of the west coast than to those of the north east coast of the North Island. Thus it is possible that Est‐4 alleles are selectively maintained in response to an environmental factor.  相似文献   

5.
Public perception has been that an apparent increase in the nearshore occurrence of white sharks Carcharodon carcharias in False Bay, on the south coast of South Africa, can at least be partly attributed to beach-seine (treknet) operations attracting sharks into this coastal area. To assess the merit of these concerns, all available beach-seine catch-and-effort data from the False Bay fishery over a 32-year period were analysed. A total of 27 cartilaginous species from 15 families was recorded in around 11 400 hauls from 1974 to 2006. Most (98%) of these comprised small benthic invertebrate feeders such as smooth houndshark Mustelus mustelus and lesser guitarfish Rhinobatos annulatus. Large sharks such as C. carcharias and ragged-tooth shark Carcharias taurus were rare, occurring in <0.2% of hauls. The only medium to large sharks that occurred frequently (15% of hauls) in any appreciable numbers (0.3 per haul) were bronze whalers Carcharhinus brachyurus. The relatively high numbers of C. brachyurus compared with C. carcharias, their overlapping size distributions and the difficulty of identifying sharks from a distance, suggests that many of the sharks observed following beach-seine nets are the bronze whalers. Overall, the frequency of occurrence of C. carcharias in the nets is much lower than would be predicted from the high number of observations in the nearshore region. Furthermore, beach-seine fishing rights in False Bay have been reduced from around 170 in the 1970s to five at present. There has been no corresponding decrease in shark incidents. On the contrary, shark incidents have increased from two in the 1970s to six during the period 2000–2005. Overall, there appears to be no strong link between beach-seine activity and human incidents with white sharks in False Bay.  相似文献   

6.
Data from 36 whale shark (Rhincodon typus Smith, 1828) sightings off north‐east North Island, New Zealand are summarised. Sightings were concentrated over the outer shelf and shelf break in areas influenced by the East Auckland Current at sea surface temperatures (SST) of 21–24°C. Sightings occurred from late spring to early autumn (November‐April) but were most frequent in midsummer (February) when upwelling along the north‐east shelf is weakest. The data indicate whale sharks occur off north‐east New Zealand most summers, including those when SST is colder than usual. A cluster of sightings and three observations of whale sharks feeding on schools of anchovy (Engraulis australis) near Whale Island, Bay of Plenty, suggest whale sharks may aggregate seasonally in this area. Estimated total lengths (TL) of 26 whale sharks ranged from 3.5 to 15 m, with 73% between 6 and 9 m TL.  相似文献   

7.
Catches from competitive shore-anglers, inshore boat-based anglers and sightings by spearfishers and divers were used to infer the spatial and seasonal movement patterns of young-of-the-year (<1.2m TL), juvenile (1.2–1.8m TL), sub-adult (1.8–2.4m TL) and adult (>2.4m TL) ragged-tooth sharks Carcharias taurus along the coast of South Africa. Adult sharks inhabited the entire coast between Maputaland in the east and St Helena Bay on the West Coast. The geographical range of sharks at earlier life-history stages decreased with size. The vast majority (93.8%) of young-of-the-year sharks recorded from competitive shore-angling club records were between East London and St Francis Bay on the East Coast, suggesting this region to be the primary nursery area for C. taurus. Estuarine systems, although utilised by young-of-the-year and juvenile C. taurus, do not form an important component of their nursery area in South Africa. Catches of pregnant and post partum females taken during the same time of year and in different areas indicated a biennial reproductive cycle. C. taurus appears to display a high degree of affinity for particular reefs. The reason some reefs are chosen over others, despite having similar physical characteristics, remains unclear. A significant increase in the number of C. taurus caught in competitions held by the Border Rock and Surf Angling Association between 1984 and 2004 suggests an increase in the abundance of C. taurus.  相似文献   

8.
It is not known whether sharksuckers have positive or negative effects on their hosts, partly because this association is difficult to study in free‐ranging fish. I observed the behaviour of sharks with and without sharksuckers, to determine whether the hosts actively avoid sharksuckers. Wild blacktip sharks, Carcharhinus limbatus, took evasive actions when sharksuckers, Echeneis naucrates, attached to them, presumably to escape from skin irritation or hydrodynamical drag caused by the sharksuckers. Sharksuckers were most often attached to the belly or back of the shark, and sharks reacted most strongly to sharksuckers on their heads, sides, and dorsal fins. Observations of two captive bull sharks, Carcharhinus leucas, indicated that swimming speed increased when sharksuckers were attached. This paper supports the hypothesis that sharksucker attachment irritates sharks, and that the relationship between the two is best viewed as a subtle host–parasite interaction.  相似文献   

9.
搁浅、误捕和救助记录是研究野生动物分布和获取其基本生物学数据的重要来源,尤其是对那些缺少系统性野外调查的物种。本研究收集了福建沿海2006—2019年间鲸鲨（Rhincodon typus）的搁浅、误捕和救助记录,初步探讨福建沿海鲸鲨的时空分布情况,并提出相应的保护对策。共收集福建沿海鲸鲨搁浅、误捕和救助记录30例,包括搁浅10例、误捕18例和救助2例,其中福州鲸鲨记录大部分在平潭岛附近,这可能与平潭海域上升流带来的丰富生物资源有关;所有记录中有28例（93.3%）发生在6—10月,表明夏秋季可能是鲸鲨在福建沿海活动的高峰期。此外,有体长记录的22条鲸鲨中,17条（77.3%）为幼年个体,可能是因为幼年鲸鲨偏好在高生产力的近岸海域聚集以获取充足的食物,因此也更容易搁浅或被误捕。较多的误捕记录（60.0％）提示渔业活动对鲸鲨有较大威胁。因此,建议建立全省甚至全国性的鲸鲨搁浅误捕数据库,进一步严格和规范渔业管理,改进渔具以降低误捕鲸鲨的概率,加强对公众（特别是渔民）的宣传教育,以更好地保护这一濒危物种。  相似文献   

10.
本研究于2020年7月在大亚湾及大鹏半岛沿岸开展造礁石珊瑚的分布、覆盖率、死亡率、硬珊瑚补充量和物种多样性调查。结果表明：24个站位共发现造礁石珊瑚9科17属44种以及5个未定种,其中裸肋珊瑚科的种类最多,有7属27种,其次为鹿角珊瑚科和滨珊瑚科,均有2属6种;中央列岛沿岸造礁石珊瑚平均覆盖率为12.0%,三门岛沿岸平均覆盖率为12.9%,大鹏半岛沿岸平均覆盖率为5.2%;以坚实滨珊瑚（Porites solida）、翼形蔷薇珊瑚（Montipora peltiformis）、五边角蜂巢珊瑚（Favites pentagona）和多孔同星珊瑚（Plesiastrea versipora）等为优势种;造礁石珊瑚物种多样性较高。与历史数据相比,大亚湾及大鹏半岛沿岸造礁石珊瑚退化严重,活珊瑚覆盖率锐减,优势种由分支状珊瑚逐步转变为皮壳状或亚团块状珊瑚。此外,本研究构建了近岸造礁石珊瑚生态脆弱性评价体系,并对目前大亚湾及大鹏半岛沿岸造礁石珊瑚进行了生态脆弱性评价。结果显示,中央列岛、三门岛和大鹏半岛东侧海域造礁石珊瑚处于低或中脆弱状态;较场尾、杨梅坑、西冲和大鹏半岛西侧海域造礁石珊瑚处于高或很高脆弱状态,在环境压力影响下其受损可能性较高。在海水养殖、渔业捕捞、滨海旅游和船舶航行等日益频繁的人类活动下,大亚湾及大鹏半岛沿岸造礁石珊瑚整体处于中高脆弱状态,建议加强珊瑚礁监测,并采取相应的保护措施。  相似文献   

11.
The Cape gannet is endemic to the southern African coast where it currently breeds at six islands: Mercury, Ichaboe and Possession off South West Africa and Bird (Lambert's Bay), Malgas and Bird (Algoa Bay) off South Africa. Previously, breeding also occurred at Hollams Bird, Halifax and Seal (False Bay) Islands. Equivocal records for Marcus, Dassen and Dyer Islands are not accepted. Off South West Africa, gannets were breeding at Hollams Bird, Mercury and Ichaboe Islands at least as early as 1828, but they only occupied Halifax and Possession Islands sometime between that date and c. 1885, possibly as a result of displacement of gannets from Ichaboe Island during exploitation of accumulated guano deposits in the early 1840s. Gannets bred at Hollams Bird Island until at least 1938, but had ceased breeding at Halifax Island by 1928. Off South Africa the earliest records of breeding are 1648, 1687, 1755 and 1912 for Malgas, Seal (False Bay), Bird (Port Elizabeth) and Bird (Lambert's Bay) Islands respectively. Gannets have not been reported at Seal Island since the late 17th century. On the west coast of Africa the Cape gannet is a regular nonbreeding winter visitor as far north as 4°20′N 6°00′E, but west of 6°E it is rare. On the east coast of Africa it is a common winter visitor as far north as Delagoa Bay, but farther north it is rare. Within its normal range the Cape gannet seldom occurs farther off shore than 100 km; it hardly ever moves inland. Aerial censuses of Cape gannets at breeding islands in 1967, 1969, 1978, 1980 and 1981 are compared with an aerial census conducted in 1956 and other published estimates of abundance. Between 1956 and 1980 the estimated number of breeding pairs at all colonies decreased from c. 150 000 to c. 80 000 and numbers decreased at all three extant gannetries off South West Africa. These decreases are attributed to a greatly diminished food resource following the collapse of the South West African pilchard stock after the late 1960s. The number of gannets decreased at Bird (Lambert's Bay) and Malgas Islands between 1956 and the late 1960s but subsequently increased, trends that are related to performances of the Western Cape pilchard and anchovy resources respectively. At Bird Island (Algoa Bay) gannets were up to 3,5 times more abundant in the late 1970s than in 1956. Other marine resources located east of Cape Point have shown similar large increases in recent years. Rates of increase of gannets at islands off South Africa during the 1970s would have required an unrealistically high survival for the first year had other population parameters remained constant. It is possible that birds emigrated from the South West African Islands. Few gannets have been reported oiled, and conservation of the species seems to be mainly affected by greatly reduced prey availability and injudicious guano harvesting. Human exploitation of juvenile gannets off the West African coast is difficult to assess.  相似文献   

12.
南澳岛是广东南澳县的主岛, 周边海域的环境保护被置于当地社会经济发展的重要位置。为此, 2004年 5月、7月选择以水产养殖为主的后江湾和白沙湾及以旅游为主的青澳湾作为研究对象, 对南澳岛海域重金属的 含量、分布、富集及污染状况进行了调查与评价。结果表明该海域重金属元素的平均含量为Cd: 0.19mg.kg-1, Cr: 26.86mg.kg-1, Cu: 20.71mg.kg-1, Ni: 22.78mg.kg-1, Pb: 35.67mg.kg-1, Zn: 79.48mg.kg-1, 低于近岸经济发达海域, 但高于受人类活动影响较小的外海; 在分布特征上表现为湾口高于湾内, 养殖区高于非养殖区的总趋势, 但在各海湾之间重金属含量并无显著差异, 表明南澳岛海域重金属主要来源于地表径流输入。该海域以城市污水中代表元素Cu (Cf = 2.75), Pb (Cf = 2.27)富集为主; 以海洋沉积物质量标准、沉积物质量基准和美国太平洋沿岸基线值评价, 南澳岛海域环境质量均处于健康状态, 但其潜在污染效应仍值得关注。  相似文献   

13.
An integrated telephone and on-site questionnaire survey was used to estimate total shark fishing effort and specific catch of the ragged-tooth shark Carcharias taurus by coastal club-affiliated shore-anglers, primarily along the east coast of South Africa. Mean total shark fishing effort was estimated to be 37 820 fisher-days year?1 (95% CI = 28 281–47 359 fisher-days year?1) with a mean cpue of 0.073 C. taurus fisher?1 day?1 (95% CI = 0.068–0.078 fisher?1 day?1). Cpue for C. taurus varied significantly along the coast and ranged from a high of 0.260 fisher?1 day?1 in the Eastern Cape to zero fisher?1 day?1 on the West Coast. The total number of C. taurus caught annually by coastal club anglers was estimated at 1 764 fish year?1 (95% CI = 321–3 207 fish year?1). The majority (92.1%) of young-of-the-year sharks (<1.2m total length, TL) were recorded between East London and Jeffreys Bay, suggesting that this may be the primary nursery area for C. taurus. Post-release mortality ranged from 3.8% for young-of-the-year sharks to 18.5% for adult sharks (>2.4m TL). The majority (76.2%) of anglers interviewed stated that they now fished less for sharks since the banning of vehicles on beaches in December 2001. As a result of this ban, almost half (49.2%) of interviewed anglers stated that they now fished more for non-cartilaginous species.  相似文献   

14.
Nursery grounds of the tarakihi Cheilodactylus macropterus (Bloch & Schneider) were discovered in 1963–72 mainly off the south‐western coast of the North Island, in Tasman Bay, along the entire eastern coast of the South Island, and around the Chatham Islands. They occurred at depths of 20–100 m, and mostly between 10 km and 30 km from shore. The tarakihi nurseries had a dense and varied invertebrate bemthic epifauna dominated by sponges and small corals. Few signs of nurseries were found in. other New Zealand waters, in spite of the existence of major spawning grounds there. It is not known with which spawning grounds the various nursery grounds are linked.

The Tasman Bay nursery ground is 18–33 km wide and about 75 km long, with a surface area of about 2000 km2. There is a rich demersal fish fauna (37 species were recorded) dominated by tarakihi, red gurnard Chelidonichthys kumu (Lesson & Garnot), snapper Chrysophrys auratus (Bloch & Schneider), and leathei'iacket Novodon convexirostris (Guenther). The young tarakihi occur at depths of 20–45 m and concentrate during winter in the warmer deeper water. They first appear in trawl catches in summer, towards the end of their first year (assumed birthdate is 1 March), and stay on the nursery until the age of 3 y. They occur in the deeper water off the nursery during their fourth and fifth year and depart during their sixth year, possibly for the spawning grounds off the west coast of the South Island. The mean lengths at the ages of 15, 27, and 39 months were 12.6, 18.0, and 24.0 cm respectively in 1970. There was some variation in growth rate within the nursery ground, but the age groups could nevertheless be recognised easily from, length frequency modes. Monthly modal lengths showed that growth slows down in winter. Evidence for fluctuations in year class strength was found; year classes 1966 and 1969 were weak and year class 1968 was strong.

The vulnerability of tarakihi less than 4y old to commercial New Zealand trawl gear is low, and the local fishing fleets do no serious damage to the habitat on the nursery grounds. However, a large part of the tarakihi nursery grounds off the east coast of the South Island lies outside the territorial fishing zone. Intensive fishing on these grounds by large foreign vessels using heavy trawl gear could have an adverse effect on the habitat of the young tarakihi in this region.  相似文献   

15.
From 1987 to 2005, numbers of African penguins Spheniscus demersus breeding in South Africa's Western Cape Province increased by about 50%. Numbers decreased at the four northernmost colonies in the region: Lambert's Bay and the three colonies in Saldanha Bay, although at Jutten Island the decrease is inferred from an estimate for 1987, derived from interpolation. Numbers also decreased at Geyser Rock and Dyer Island on the South Coast. At five colonies between Saldanha Bay and Dyer Island there were large increases. At a sixth colony in that region, Seal Island, where Cape fur seals Arctocephalus pusillus pusillus limit breeding space, numbers remained stable. At two colonies that were initiated in the early 1980s, Robben Island and Boulders, increases were initially rapid (>20% per annum) and matched growth of the South African stock of sardine Sardinops sagax. Strong growth at Dassen and Vondeling islands, between Robben Island and Saldanha Bay, was observed from about 1996–2002, when there was a large increase in the biomass of pelagic fish off South Africa. Increases at colonies between Saldanha Bay and Boulders slowed after 2002, whereas the colony at Dyer Island stabilised at that time. In 2003, a new colony was initiated east of Dyer Island at De Hoop Nature Reserve. These latter trends followed an eastward shift in the distribution of sardine. Small penguin colonies may act as foci for growth in a period when the distribution of prey is changing. Hence, it is important that they be maintained, especially those that, if lost, would increase the isolation of regional populations. Some of the small colonies are less susceptible to oil spills than colonies in the proximity of harbours, and for that reason also are important.  相似文献   

16.
珠江口红树林基围养殖生态开发模式评述   总被引：2，自引：0，他引：2       下载免费PDF全文
起源于珠江三角洲的红树林基围(land-based enclosure)养殖传统模式是红树林可持续利用和生态开发范例之一。本文介绍了珠江口红树林基围养殖生态开发模式的3个个例: 仅存香港米埔红树林自然保护区的传统基围养殖运作历史和演变, 及其候鸟生境、养殖、观鸟、环境教育综合功能的实现; 珠海淇澳岛大围湾红树林传统和粗放式基围养殖试验和围内水位盐度等环境条件变化对红树林生长影响的研究; 伶仃洋东岸海上田园红树林海水种植-集约式养殖系统试验和红树林净化水质研究。在珠江口红树林保护管理及海域污染防治过程中建议重视红树林可持续利用模式的研究和推广, 建立新的基围养殖示范区, 大力推广红树林基围养殖的生态开发模式, 探索毁林养殖区红树林友好式整治模式, 改善红树林基围养殖技术提高养殖产量, 加强红树林基围养殖系统相关科学研究。  相似文献   

17.
确定自然海岸特征是海岸修复中的重要内容,但是在开发后弃管的无居民海岛却面临缺少历史资料参考的困难。在大连普兰店湾中部前大连岛的研究证明,依据历史影像和现存海岸地质地貌情况可以分析确定原自然海岸位置及性质。1972年KH 卫星影像表明当时的前大连岛仍然保持自然海岸形态,海岸位置在2020年海岸后 方的岛屿陆域内部。结合2020年海岸地质考察结果可以进一步确定1972年的前大连岛东部、西部分布海蚀崖形式的基岩海岸,南部、北部则分布砾石质海岸。1972—2020年,前大连岛自然海岸全部变化为人工海岸,海岸长度也从约2.38 km 增加至约3.12 km。  相似文献   

18.
A total of 772 bull sharks Carcharhinus leucas was caught in Natal's protective "shark nets" between 1978 and 1990. Confusion in distinguishing C. leucas from C. amboinensis resulted in their catch data being combined from 1966, when data collection began, to 1977. The catch rate of the species pair declined until 1977, recovered until the mid 1980s, but subsequently declined again. The trend in catch rate of C. leucas alone for the period 1978–1990 was similar, with minima of 0,70 sharks·km-net?1·year?1 in 1978 and 0,95 in 1990, and a maximum of 2,08 in 1986. Recaptures of six tagged sharks suggest that the species is not highly migratory. Catches, particularly of immature sharks, were highest at the northernmost beaches. Most bull sharks were caught in summer and in turbid water (mean water clarity 2,0 m). The sex ratio of the catch was 1 male to 1,3 females. Sizes ranged from 74 to 213 cm precaudal length, with modes of 141–145 cm (males) and 171–175 cm (females). Size at maturity for both sexes was between 180 and 190 cm. The mating season was prolonged but with a summer peak. Seven gravid females were examined; the mean litter size was 8,7 embryos and size at birth was approximately 55 cm. Fluke infections were observed on 9 per cent of animals examined. As size increased there was a shift in diet, in terms of frequency of occurrence, from teleost to elasmobranch predominance. There was a high incidence of benthic and demersal species in the stomachs. Minor prey groups included mammals, birds, turtles, molluscs and crustaceans. Scavenging appeared to be important.  相似文献   

19.
Identifying nearshore waters that serve as important habitats for neonate and juvenile sharks is crucial for effective fisheries management. This study examined the abundance of neonate and juvenile dusky sharks Carcharhinus obscurus within the Port of Ngqura, on the south-east coast of South Africa, between September 2006 and August 2007 using a combination of shore-angling catches and mark-recapture data. During this period, the port was non-operational and still undergoing construction. A total of 480 dusky sharks, ranging in size from 50 to 123 cm (precaudal length), was captured. Catch per unit effort was greatest between October and February, peaking in November at 0.51 sharks angler–1 h–1. Of the 219 C. obscurus tagged and released during the study period, 37 (16.9%) were recaptured. Sharks were at liberty from 0 to 409 days with the majority (89.2%) recaptured within the port. Using a Jolly-Seber open population model, the abundance of sharks within the port was estimated at 552 (95% CI: 422–765). Annual apparent survival probability was 0.38 (95% CI: 0.30–0.46), with an average annual recapture probability of 0.28 (95% CI: 0.19–0.39). This study demonstrates that the Port of Ngqura is an important summer habitat and core activity zone for both neonate and juvenile dusky sharks.  相似文献   

20.
Seasonal changes in ovarian activity were investigated in New Zealand turbot Colistium nudipinnis (Waite 1910) and brill Colistium guntheri (Hutton 1873), collected by commercial trawlers along the west coast of the South Island of New Zealand. Both species demonstrated group synchronous oocyte development, with a capacity for multiple ovulations within a reproductive season. During a 17‐h trawl survey, ovulated turbot were caught between 1500 and 2030 h, indicating a daily spawning rhythm. The turbot and brill spawning seasons were prolonged (late autumn to mid summer). A protracted spawning season confers some advantages in aquaculture.  相似文献   

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