On estimating diversity in species-rich fish assemblages: an example with coral-reef fishes of eastern Indonesia

A new procedure for estimating fish species richness in open or semi-open habitats is presented with unpublished data on the coral-reef fish assemblages of Raja Ampat, eastern Indonesia, known as the centre of marine biodiversity in the western Pacific.     

Distribution and abundance of fish in deep-sea coral habitats

Experimental fishing with long-lines and gillnets was conducted on the continental shelf off southwestern Norway between 150 and 350 m depth. Abundance and distribution of redfish (Sebastes marinus L., 1758), ling (Molva molva L., 1758), and tusk (Brosme brosme Ascanius, 1772) were quantified in Lophelia pertusa (L., 1758) coral reefs and in non-coral habitats. The largest catches of redfish were made with long-line fleets set in coral reef habitats. Ling and tusk were also most numerous in coral habitats, although not statistically significant. Fish caught in coral habitats tended to be larger in size than in non-coral habitats. The diet of redfish, tusk and ling included the same prey groups in all habitats, but they differed at the species level. Lophelia-reefs may provide a profitable feeding place for tusk. For the planktivorous Sebastes, on the other hand, their affinity to the reefs seems primarily to be related to the physical structure offered by the reefs.     

Is the proportion of clonal species higher at higher latitudes in Australia?

We provide a large‐scale quantification of the relationship between latitude and the proportion of species with clonal reproduction. Parasite pressure is thought to be higher at low latitudes, while abiotic stress is thought to be higher at high latitudes. We therefore predicted that there would be a higher proportion of clonal species at high latitudes than at low latitudes. We collected data of 4386 native seed plant species from 446 genera and 99 families present in ABRSFlora of Australia. Species' occurrence records were taken from the Atlas of Living Australia, including 817 450 species‐site combinations spanning 34.5° of latitude. Logistic regression showed that the proportion of clonal species significantly increased with latitude, rising from 3.3% clonal species at 9.25°S to 26.7% clonal species at 43.75°S. The overall average proportion of clonal species in Australian seed plants was 9.4%. This study adds to our growing understanding of dramatic latitudinal gradients in the way plants grow and reproduce. It also reveals that Australian vegetation contains a relatively low proportion of clonally reproducing species.     

Postsettlement movement patterns and homing in a coral-associated fish

Coral-associated gobies are highly specialized reef fishes withhigh host-coral fidelity. Flexibility in habitat choice, however,is important to compensate for potential habitat alterationor loss, but detailed information about the postsettlement movementbehavior of such gobies is lacking. We examined movement patternsin Gobiodon histrio, both under natural conditions and duringsubsequent field experiments, involving breeding pair or partnerremoval from 3 of the 4 investigation plots. Additionally, weinvestigated homing behavior, and 2 aquaria experiments weredesigned to assess home coral and partner recognition of adultfish taken from breeding pairs. Under natural conditions, themovement rate was high for single adults, whereas breeding pairsshowed high home-coral fidelity. Manipulations revealed littlechange of natural patterns except in single adults, which slightlydecreased their movement rate in the breeding pair removal plot.In the homing experiment, 17% of tested fish returned to theirhome coral even after displacement of 4 m, and homing successwas much higher at shorter distances (100% at 0.5 m, 53% at2.25 m). In the aquarium, G. histrio exhibited higher recognitionof its home-coral colony (75%) than of its breeding pair partner(60%). Our study shows that G. histrio frequently moves betweencorals, although this depends on the social status (juvenile,single adult, breeding pair) of the individuals. The high proportionand movement rate of single adults indicate low sensitivityto habitat alteration but also limited high-quality habitatsin which breeding pairs could be established. Hence, vulnerabilityto habitat loss increases when individuals breed.     

三亚珊瑚礁水域纤毛虫种类组成和数量分布及与环境因子的关系

2004年8月通过对三亚珊瑚礁水域纤毛虫进行表、底层采集分析,共鉴定6纲14目33属58种浮游纤毛虫,其中旋毛纲41种,叶口纲6种,寡膜纲5种,叶咽纲4种,前口纲和伪纤毛纲各1种。在14个目中,以旋毛纲环毛亚纲砂壳目纤毛虫种类最多,达到31种。主要优势种为布氏拟铃虫 Tintinnopsis bütschlii、小拟铃虫 Tintinnopsis minuta、丁丁急游虫Strombidium tintinnodes和具沟急游虫Strombidium sulcatum等,底层纤毛虫数量和种类都较表层高,底、表层平均丰度分别为375个/L和346 个/L,表、底层纤毛虫种类差异明显,表层主要由浮游纤毛虫组成,以旋毛纲环毛亚纲砂壳目纤毛虫为主,急游目纤毛虫次之;而底层主要由缘毛目组成,如长圆靴纤虫 Cothurnia oblonga、透明鞘居虫Vaginicola crystalline、钟虫Vorticella sp.以及吸管目的壳吸管虫 Acineta sp. 等。结果显示,在活珊瑚覆盖率高的站位（S4,S7和S9）纤毛虫数量明显低于珊瑚覆盖率低或没有珊瑚覆盖的站位,这暗示了珊瑚对纤毛虫的摄食作用。典型对应分析结果表明,影响三亚湾海域纤毛虫分布的主要因素有Chla、颗粒悬浮物SS和活性磷,以及水体溶解有机碳含量。通过对纤毛虫数量与环境因子关系的分析表明,三亚湾珊瑚礁水域纤毛虫的数量与叶绿素呈明显的正相关性。     

The Structures and Dynamics of Fish Communities in an Okinawan Coral Reef: Effects of Coral-based Habitat Structures at Sites with Rocky and Sandy Sea Bottoms

Although there have been many studies on ecological factors responsible for the organization of reef fish communities, most of the studies have focused on isolated habitats. However, findings from isolated habitats cannot necessarily be applied to fish communities in other habitats (e.g., a continuous habitat). In this study, therefore, we examined the structures of fish communities (abundance, species richness and species composition), and the dynamics of fish communities (seasonal changes in abundance, species richness and species composition) over a 2-year period in two different habitats (continuous habitat and isolated habitat) in an Okinawan coral reef. We established eight permanent quadrats (8m × 8m) on a rocky reef flat (continuous habitat) and rock reef patches surrounded by a sandy sea bottom (isolated habitat). The abundance and species richness of fishes such as pomacentrids, labrids, chaetodontids and acanthurids were greater in quadrats located in the continuous habitat, whereas those of blenniids, gobiids and mullids were greater in quadrats located in the isolated habitat. This caused marked differences between the fish community structure at the two sites. Seasonal and annual changes in fish community structure were relatively small at the continuous habitat site (>0.7 similarity based on C index) but were large at the isolated habitat site (C < 0.4), indicating that the fish community structure was relatively stable at the continuous habitat site but unstable at the isolated habitat site throughout the study period. Spatial differences between the fish community structures in the four quadrats at the continuous habitat site were small (C > 0.65 in most sites), but these differences were large at the isolated habitat site (C < 0.4). Our findings suggest that habitat structure (spatial arrangement of habitats) affects both spatial and seasonal differences in the reef fish community structure. The results also suggest that the main mechanisms underlying organization of reef fish communities in continuous and isolated habitats are different.     

Coral bleaching, reef fish community phase shifts and the resilience of coral reefs

The 1998 global coral bleaching event was the largest recorded historical disturbance of coral reefs and resulted in extensive habitat loss. Annual censuses of reef fish community structure over a 12-year period spanning the bleaching event revealed a marked phase shift from a prebleach to postbleach assemblage. Surprisingly, we found that the bleaching event had no detectable effect on the abundance, diversity or species richness of a local cryptobenthic reef fish community. Furthermore, there is no evidence of regeneration even after 5–35 generations of these short-lived species. These results have significant implications for our understanding of the response of coral reef ecosystems to global warming and highlight the importance of selecting appropriate criteria for evaluating reef resilience.     

Fish sampling in the marine-dominated Kariega Estuary,South Africa,using a demersal otter trawl: day/night effects

Very few demersal fish assemblage studies using otter trawls in estuaries have been done in South Africa and none of these have tested for the effects of diel period. This study aimed to test whether diel period affects otter trawl catches in the clear, permanently open Kariega Estuary in terms of both species composition and abundance. Fish were sampled by day and night from 30 October to 1 November 2007 at 15 sites using an otter trawl. More species were collected at night, when there were higher catch rates for all key species, with the exception of Rhabdosargus holubi, which was more abundant during the day. Overall assemblages collected by day and by night were similar, with six species accounting for over 90% of the catch in both day and night samples. Both day and night samples reflected differences related to region, with the highest mean CPUE during day and night sampling being recorded in the head region.     

Effects of habitat complexity on forest beetle diversity: do functional groups respond consistently?

We examined the responses of a beetle assemblage to habitat complexity differences within a single habitat type, Sydney sandstone ridgetop woodland, using pitfall and flight‐intercept trapping. Six habitat characters (tree canopy cover, shrub canopy cover, ground herb cover, soil moisture, amount of leaf litter, and amount of logs, rocks and debris) were scored between 0 and 3 using ordinal scales to reflect habitat complexity at survey sites. Pitfall trapped beetles were more species rich and of different composition in high complexity sites, compared with low complexity sites. Species from the Staphylinidae (Aleocharinae sp. 1 and sp. 2), Carabidae (Pamborus alternans Latreille), Corticariidae (Cartodere Thomson sp. 1) and Anobiidae (Mysticephala Ford sp. 1) were most clearly responsible for the compositional differences, preferring high complexity habitat. Affinities between general functional groupings of pitfall‐trapped beetles and habitat variables were not clear at a low taxonomic resolution (family level). The composition and species richness of flight‐intercept‐trapped beetles were similar in high and low complexity sites. Our study demonstrates that discrete responses of the various functional groups of beetles are strongly associated with their feeding habits, indicated by differing habitat components from within overall composite habitat complexity measures. Although habitat preferences by beetle species may often reflect their foraging habits, clarification of the causal mechanisms underpinning the relationships between habitat complexity and beetles are critical for the development of general principles linking habitat, functional roles and diversity.     

青岛崂山青山湾人工鱼礁区及附近海域鱼卵仔稚鱼种类组成与数量分布

为研究人工鱼礁对产卵鱼类的诱集效果和庇护效应,2014—2015年对青岛崂山青山湾海域人工鱼礁区及附近海域鱼卵和仔稚鱼的种类组成和数量分布进行了水平和垂直拖网调查. 2014年春、夏、秋3个季节的7个航次调查中,共采集鱼卵7306粒、仔稚鱼52尾,隶属于4目9科11属12种;2015年同期进行的13个航次调查中,共采集鱼卵10373粒、仔稚鱼159尾,隶属于6目11科14属15种.2年间鱼卵和仔稚鱼样品均以鲈形目数量最多,鲽形目次之,其中鱼卵样品中仅有少鳞鱚和短吻红舌鳎构成优势种;仔稚鱼样品以少鳞鱚优势度最高,但不存在仔稚鱼优势种.鱼卵和稚鱼的高优势度物种的季节间演替明显.春、夏、秋季鱼类浮游生物群落Margalef丰富度指数、Shannon多样性指数和Pielou均匀度指数平均值均较低,说明该海域鱼类浮游生物群落结构稳定性较低.2年间所采集物种对应的成鱼平均营养级分别为3.71和3.78,均属第三营养级中的低级肉食性鱼类,绝大多数为暖温种,无冷温性种类,表现出明显的暖温带特点.综合分析认为,人工鱼礁区鱼类浮游生物群落的多样性相对较高,这与鱼礁区流速和流场特征及复杂的空间异质性有关.     

Soft-bottom assemblages of Paterson Inlet,Stewart Island

Abstract

The soft-bottom biota of subtidal areas of Paterson Inlet, Stewart Island, is described on the basis of data collected during cruises (1977 and 1979) in search of Braichiopoda. Two associations are recognised within the areas sampled, and their structure is compared with that of soft-bottom biotas elsewhere in New Zealand. The widespread occurrence of patch-forming bryozoans (especially Cinctipora elegans) on sandy gravels on the southern New Zealand shelf IS recognised.     

The influence of residential and cottage development on littoral zone fish communities in a mesotrophic north temperate lake

We used the rapid visual technique (RVT), an underwater visual assessment method developed in marine environments, to assess the influence of residential and cottage development on littoral zone fish communities in Pigeon Lake, a shallow, mesotrophic Canadian lake with extensive shoreline disturbance. We used RVT to assess 135 sites, stratified by degree of residential and cottage development (undeveloped, moderately developed, highly developed) and habitat type (three substrate/vegetation categories). Sites with different degrees of residential and cottage development did not differ significantly in species richness. When the RVT site scores of each species life stage (young-of-year, juveniles and adults) were compared among development categories, only 11% of species life stages showed significant differences; all were most abundant in moderately developed sites. Habitat had a greater influence than development on within-taxon abundance, as 46% of species life stages showed significant among-habitat differences in RVT score. The absence of significant fish community differences between developed and undeveloped sites may be due to the shallowness, extensive macrophyte cover and raised shorelines from the construction of the Trent-Severn Waterway. However, there do appear to be changes in the fish community over the last 35 years, as six cyprinids and one cyprinodont species that were present in Pigeon Lake in the 1970s were not detected by our sampling. RVT provided comparable data to that obtained by straight line transects on the relative abundance of species in the lake, but RVT was more effective at detecting species and life stages present at individual sites.     

青岛近岸水域春、秋季鱼类群落结构

根据2004年春、秋季渔业资源底拖网调查数据,应用单元和多元统计方法分析了青岛近岸水域春、秋季鱼类群落结构。春、秋季调查分别渔获31、32种鱼类,平均每网渔获量分别为7.36kg/h和2.99kg/h,优势种类主要包括赤鼻棱鳀Thrissa chefuensis、大泷六线鱼Hexagrammo sotakii、方氏云鳚Enedrias fangi、黄鳍刺鰕虎鱼Acanthogobius flavimanus、细纹狮子鱼Liparis tanakai和长条蛇鲻Saurida elongata等。聚类分析表明,春、秋季青岛近岸水域鱼类群落都可划分为3个站位组,分别对应于北部、中部和南部调查水域。不同站位组的优势种组成变化较大,不同站位组间种类组成差异显著。分析了造成站位组内种类组成相似的特征种和造成不同站位组间相异的分歧种。不同站位组的特征种不同。赤鼻棱鳀、大泷六线鱼、黄鳍刺鰕虎鱼、方氏云鳚、星康吉鳗Conger myriaster、角木叶鲽Pleuronichthys cornutus和细纹狮子鱼是春季所有站位组间的分歧种;赤鼻棱鳀、白姑鱼Argyrosomus argentatus、大泷六线鱼、带鱼Trichiurus lepturus、短吻红舌鳎Cynoglossus joyneri、方氏云鳚、细条天竺鱼Apogonichthys lineatus、小黄鱼Pseudosciaena polyactis和矛尾鰕虎鱼Chaeturichthys stigmatias是秋季所有站位组间的分歧种。大多数特征种也是不同站位组间的分歧种,主要是由于这些种类的数量分布的空间变化造成的。青岛沿海鱼类群落结构存在明显的时空异质性。     

Effects of Habitat Connectivity on the Abundance and Species Richness of Coral Reef Fishes: Comparison of an Experimental Habitat Established at a Rocky Reef Flat and at a Sandy Sea Bottom

Coral reef fish assemblages are widely recognized for the coexistence of numerous species, which are likely governed by both coral diversity and substratum complexity. However, since coral reefs provide diverse habitats due to their physical structure and different spatial arrangements of coral, findings obtained from an isolated habitat cannot necessarily be applied to fish assemblages in other habitats (e.g. continuous habitats). The aim of this study, therefore, was to determine by a field experiment whether habitat connectivity (spatial arrangement of coral colonies) affects abundance and species richness of fishes in an Okinawan coral reef. The experiment consisted of transplanted branching coral colonies at a 4m×8m quadrat at both a rocky reef flat and sandy sea bottom. Generally, the abundance of fishes was greater at the sandy sea bottom, especially for three species of pomacentrids, one species of labrids, one species of chaetodontids and two species of apogonids. Species–area curves showed that the species richness of fishes was significantly greater in the quadrat at the sandy sea bottom at 3, 6 and 9 months after the start of the experiment. The rate of increase in abundance of fishes per area was significantly greater in the quadrat at the sandy sea bottom over the study period. The results of rarefaction analyses showed that the rate of increase in species richness per abundance was significantly higher in the quadrat at the sandy sea bottom in the juvenile settlement period, indicating that the magnitude of dominance by particular species was greater at the sandy sea bottom habitat. Our findings suggest that habitat connectivity affects the abundance and species richness of coral reef fishes, i.e. the isolated habitat was significantly more attractive for fishes than was the continuous habitat. Our findings also suggest that the main ecological factors responsible for organization of fish assemblage at a continuous habitat and at an isolated habitat are different.     

Temperature influences habitat preference of coral reef fishes: Will generalists become more specialised in a warming ocean?

Climate change is expected to pose a significant risk to species that exhibit strong behavioural preferences for specific habitat types, with generalist species assumed to be less vulnerable. In this study, we conducted habitat choice experiments to determine how water temperature influences habitat preference for three common species of coral reef damselfish (Pomacentridae) that differ in their levels of habitat specialisation. The lemon damselfish Pomacentrus moluccensis, a habitat specialist, consistently selected complex coral habitat across all temperature treatments (selected based on local average seasonal temperatures naturally experienced in situ: ambient winter 22°C; ambient summer 28°C; and elevated 31°C). Unexpectedly, the neon damselfish Pomacentrus coelestis and scissortail sergeant Abudefduf sexfasciatus, both of which have more generalist habitat associations, developed strong habitat preferences (for complex coral and boulder habitat, respectively) at the elevated temperature treatment (31°C) compared to no single preferred habitat at 22°C or 28°C. The observed shifts in habitat preference with temperature suggest that we may be currently underestimating the vulnerability of some habitat generalists to climate change and highlight that the ongoing loss of complex live coral through coral bleaching could further exacerbate resource overlap and species competition in ways not currently considered in climate change models.