Patterns of color phase indicate spawn timing at a Nassau grouper Epinephelus striatus spawning aggregation

Nassau grouper Epinephelus striatus are a large bodied,top level predator that is ecologically important throughout the Caribbean.Although typically solitary,Nassau grouper form large annual spawning aggregations at predictable times in specific locations.In 2003,The Cayman Islands Marine Conservation Board established protection for a newly rediscovered Nassau grouper spawning aggregation on Little Cayman,British West Indies.The large size of this aggregation provides a unique opportunity to study the behavior of Nassau grouper on a relatively intact spawning aggregation.During non-spawning periods Nassau grouper display a reddish-brown-and-white barred coloration.However,while aggregating they exhibit three additional color phases:“bicolor”,“dark”,and “white belly”.We video sampled the population on multiple days leading up to spawning across five spawning years.Divers focused a laser caliper equipped video camera on individual fish at the aggregation.We later analyzed the video to determine the length of the fish and record the color phase.Our observations show that the relative proportion of fish in the bicolor color phase increases significantly on the day leading up to the primary night of spawning.The increase in the proportion of the bicolor color phase from 0.05 early in the aggregation to 0.40 on the day of spawning suggests that this color phase conveys that a fish is behaviorally and physiologically prepared to spawn.Additionally,82.7％ of fish exhibiting dark or white belly coloration early in the aggregation period suggests that these color phases are not only shown by female fish as was previously posited [Current Zoology 58 (1):73-83,2012].     

Seasonal Timing and Diel Activity of Lacustrine Brook Charr, Salvelinus Fontinalis, Spawning in a Lake Outlet

The objectives of this study were to determine (1) the seasonal timing and diel activity patterns of lacustrine brook charr when migrating to a lake outlet for spawning, and (2) the homing of reproducing individuals. In 1995, 745 individuals were captured while migrating to the spawning ground compared to 1148 in 1996. In both years, the sex ratio was not significantly different from 1:1 but females were significantly longer than males. The spawning migrations lasted about 48d and were more nocturnal (between 20:00 and 8:00h) than diurnal. The migration to the spawning ground began when water temperature decreased to 13°C and peaked when water temperature decreased from 11°C to 7°C. Peaks in migration activity were always preceded by a sudden decrease followed by an increase in temperature. The spawning migration lasted until the third week of October, when water temperature varied between 3°C and 8°C. Males, especially larger ones, arrived on the spawning ground before females in both years. The length of males migrating to the spawning ground decreased during the spawning season while the females' length showed no pattern. Only 9.7% of the 745 fin-clipped individuals from 1995 returned to the lake outlet to spawn in 1996. The results of this study indicate that lacustrine brook charr show similarities to other anadromous and lake-spawning salmonid populations when migrating to spawning grounds.     

Reproduction of the Nassau grouper,Epinephelus striatus (Pisces: Serranidae) and its relationship to environmental conditions

Synopsis Spawning aggregations of the Nassau grouper, Epinephelus striatus, occurring at the southern end of Long Island were investigated during the winters of 1987–1988 and 1988–1989. Fish aggregate at two specific sites around the time of the full moon in December and January, possibly not during November and almost certainly not during February. At one site the fish aggregate well inside the shelf edge while at the other they are on the dropoff into deep water. Fish migrate, probably as distinct groups of up to about 500 individuals, to the sites on or before the full moon and remain for several days. There was no significant difference in the size of males and females caught from the aggregations between years or months. Female/male sex ratio was between 5 : 1 and 3 : 1. Courtship occurred in late afternoon with spawning commencing shortly before sunset. Most spawning occurred within 10 min of sunset. Water temperatures were 25.0–25.5°C during a period of gradual decrease towards the annual minimum in February and March. Two color patterns were important in courtship and spawning. The bicolor pattern is a submissive coloration indicating a non-aggressive state acquired by both males and females near the time of spawning. The dark phase is acquired by females who are followed by numerous bicolor fish during courtship and they lead spawning events in this pattern. Spawning occurred among subgroups of the aggregation numbering 3–25 fish; gamete release was well above the bottom. Drogues deployed with the gametes either moved inshore or did not move far away from the shelf edge over the course of several days. Nassau groupers may not strictly be protogynous hermaphrodites and other groupers which form spawning aggregations may not be so either. Latitudinal shifts in spawning time may be related to water temperatures. Currents at aggregation sites do not appear to favor offshore transport of eggs. Questions of whether spawning aggregations should be protected need to be answered.     

Aggregations of <Emphasis Type="Italic">Plectropomus areolatus</Emphasis> and <Emphasis Type="Italic">Epinephelus fuscoguttatus</Emphasis> (groupers,Serranidae) in the Komodo National Park,Indonesia: Monitoring and Implications for Management

Synopsis We identify fishery management implications from a long-term monitoring program focusing on spawning aggregations of high valued reef fish in Komodo National Park (KNP), Eastern Indonesia. Management objectives of KNP are not only to protect biodiversity, but also to conserve spawning stocks of high-valued commercial species for the replenishment of surrounding fishing grounds. We monitored two sites twice monthly over five years for two species of grouper, Epinephelus fuscoguttatus and Plectropomus areolatus. One site had an aggregation of both E. fuscoguttatus and P. areolatus, whereas the other site contained an aggregation of P. areolatus only. Over the five years monitoring period, aggregations typically formed during each full moon between September and February. Additionally, P. areolatus occasionally aggregated during new moons between April and July. We observed spawning only once, but because formation of aggregations were correlated to a higher incidence of behavior and signs indicative of reproduction and because most fish present were adults, it is likely that the formation of aggregations was associated with spawning. Over the five years monitoring period there was a reduction in mean fish size of up to 8 cm for P. areolatus, and a reduction in numbers of aggregating E. fuscoguttatus. Despite limited protection initiated in 2001, both sites are still heavily fished by local artisanal fishers. Because the observed reductions in size and in numbers could be caused by fishing pressure, managers should follow the precautionary principle by putting additional protective management in place. Since both species are relatively long-lived, at least five years of continued monitoring may be necessary to determine the outcome of management intervention. The variability in timing of aggregation in respect to season and moon phase in P. areolatus indicates that long-term monitoring must cover the entire year and both moon phases.     

Analysis of otolith chemistry in Nassau grouper (Epinephelus striatus) from the Bahamas and Belize using solution-based ICP-MS

 We examined the utility of otolith minor and trace element chemistry, assayed with inductively coupled plasma mass spectrometry (ICP-MS), as a means of delineating population structure in the Nassau grouper (Epinephelus striatus). We characterized the elemental composition of otoliths collected in 1993 from three locations in Exuma Sound, Bahamas and from Glover Reef, Belize in 1995. A single location in Exuma Sound was sampled in 1994 to test temporal variability in otolith composition. Five elements (Ca, Zn, Sr, Ba and Pb) were routinely detected, at levels significantly above background, by solution-based ICP-MS. Results from analysis of variance of elemental data, expressed as a ratio to Ca, indicated that there were no significant differences among the Exuma locations for any element, but significant variability was found between Glover Reef and the pooled Exuma localities for Zn/Ca, Sr/Ca and Ba/Ca ratios. Significant inter-annual differences at one Exuma Sound location was restricted to Ba/Ca ratios. Discriminant function analysis correctly classified 86% and 95% of the Belize and pooled Exuma sites, respectively. Otoliths from Belize were characterized by low Zn/Ca and high Ba/Ca and Pb/Ca ratios compared to otoliths from fish collected in Exuma Sound. Although differences in Ba levels may be related to upwelling at Glover Reef, more data are needed to definitely link otolith composition with regional differences in water chemistry. Accepted: 15 February 1999     

Observations of Spawning Behaviour in Salmoninae: Salmo, Oncorhynchus and Salvelinus

Long-term data from underwater video recordings in the wild and semi-natural channels are compared to the current literature to review the reproductive behaviour of fishes in the subfamily Salmoninae. Male alternative strategies and tactics are discussed. Reproductive behaviour in Salmoninae is divided into different phases related to female nest selection, construction, and completion. Still underwater video frames are used to support conclusions drawn on spawning behaviour.     

Nest Site Selection and Spawning by Captive Bred Atlantic Salmon, Salmo salar, in a Natural Stream

Synopsis We examined the physical habitat of nest sites chosen by hatchery Atlantic salmon, Salmo salar, in a recovery program for this extirpated species in Lake Ontario, Canada. We compared the sites used by these captive bred fish to a set of random locations in a wide range of available habitats. Compared to random locations in the stream, the nest sites chosen were lower in the relative abundance of sediment size classes that are detrimental to embryo and juvenile survival. In addition, the process of nest construction by these captive bred fish further reduced the proportions of these detrimental sediments. Although captive breeding may have changed some aspects of the nest site selection and construction behaviour, it has not caused a complete loss or major alteration of the trait and thus does not preclude hatchery fish from restoration or reintroduction programs.     

Spawning behavior and haremic mating system in the corallivorous butterflyfish,Chaetodon trifascialis, at Kuroshima Island, Okinawa

Territorial and spawning behavior ofChaetodon trifascialis were investigated on a small patch of reef at Kuroshima Island, Okinawa, Japan. Three males and 8 females inhabited the reef, each individual defending a territory against conspecifics of the same sex. Each male territory included 2 or 3 female territories. In the daytime, each male frequently visited the females living in its territory. At dusk in the full or new moon periods, courtship began within the female territories, pair spawning subsequently occurring within or near those territories. When a male actively courted a female in the territory of a second male, the latter male immediately chased off the intruder. Thus, mating occurred only between a male and females living in former's territory. This is the first report of a haremic mating system among butterflyfishes (Chaetodontidae).     

Spawning of hermatypic corals in Bermuda: a pilot study

This study investigates spawning of 4 hermatypic coral species from the subtropical environment of Bermuda. Laboratory evidence of spawning behaviour is supported by synchronous field observations. Development of scleractinian planulae to postlarval stages is recorded. Diploria strigosa, D. labyrinthiformis, Montastrea annularis and M. cavernosa shed highly buoyant, pigmented eggs (300–440 µm diam.) during July to September 1986. Brief spawning periods, synchronous between conspecific colonies, were recorded for M. annularis (July and August) and M. cavernosa (August) within 1 d of the last quarter of the lunar cycle. In August, there were overlaps amongst the spawning dates of D. strigosa and the Montastrea species. Nocturnal spawning periods differed between M. annularis and M. cavernosa. This constitutes the first evidence from an Atlantic community of overlapping spawning dates amongst several faviid species, and of the accumulation of scleractinian eggs and planulae in surface slicks.     

Temporal and Spatial Trends in Spawning Aggregations of Camouflage Grouper, Epinephelus Polyphekadion, in Pohnpei, Micronesia

The aims of this investigation were to document the temporal and spatial dynamics of aggregated camouflage grouper, Epinephelus polyphekadion in Pohnpei, Micronesia, and to assess seasonal and daily patterns of spawning and reproductive behavior. Camouflage grouper aggregated and spawned adjacent to the Kehpara Marine Sanctuary (KMS), Pohnpei, Micronesia, during two consecutive months in 1998 and 1999. A combination of gonadosomatic indices, oocyte diameter analysis, and histological evidence confirmed that camouflage grouper spawned 1–2 days prior to full moon over an 8–9h period after dusk in each of the four study months. Males entered the site approximately 7 days prior to females and color variations were frequently observed. Significant differences were detected in mean size between the sexes. A series of management initiatives was initiated by the government in the 1980s to reduce fishing during aggregation periods, such as a March–April grouper sales ban, but these were largely ineffective. Following the 1998–1999 survey, several recommendations were made to halt aggregation fishing, including a commercial and subsistence catch and sales ban during spawning months, and the extension of the KMS to incorporate two additional grouper aggregations directly adjacent to it.     

The Spawning and Early Life History of the Pollan (Coregonus pollan THOMPSON) in Lough Neagh,Northern Ireland

Studies had been carried out on the local non-migratory whitefish. Spawning behaviour and light conditions on the spawning ground are recorded. After artificial spawning, embryonal development took place under controlled conditions and the larvae were reared. Detailed characteristics of swim bladder creation and differentiation of the digestive tract are given. Distribution and number of pollan larvae near the spawning area and in the open lake were examined. Data are presented concerning the growth rates of larvae and fry in captivity and under lake conditions. Ecological data related to other coregonids are discussed and compared with the present study.     

Seasonal cycles of gonadal development and plasma sex steroid levels in Epinephelus morio, a protogynous grouper in the eastern Gulf of Mexico

In a field population of the protogynous red grouper Epinephelus morio in the eastern Gulf of Mexico, females with oocytes at all stages of development were collected during the spawning season suggesting that several batches of oocytes may be released over the spawning period. Plasma oestradiol (E₂) levels were highest in ripe females whose gonads contained both cortical alveoli and vitellogenic oocytes during the breeding season. Males were still spermiating as late as August, although levels of androgens 11-ketotestosterone (11-KT) and testosterone (T) had declined from their peaks in March. A few red grouper with either perinucleolar or cortical alveoli stage oocytes were undergoing sex change both during and after the spawning period. Low levels of E₂, T and 11-KT were detected in transitionals. Proliferation of male tissue was not restricted to any specific area of the gonad but occurred in pockets within the ovarian lumen. The sequence of an increase in gonial cells along the periphery of the lamellae, increase in interstitial tissue, degradation of female elements, and formation of a sperm duct seemed to be concurrent with spermatocyte proliferation and the process of preparing the gonad to function as a testis.     

A functional analysis of food procurement in two surgeonfish species,Acanthurus nigrofuscus andCtenochaetus striatus (Acanthuridae)

Synopsis The mechanisms of food procurement in the surgeonfishesCtenochaetus striatus andAcanthurus nigrofuscus from the Great Barrier Reef were determined by functional analyses of the jaws and associated structural elements (based on myological and osteological examinations and X-ray photographs) and by video analyses of actions of the mouth and body during feeding.Acanthurus nigrofuscus has relatively robust jaw bones. The movement of the elements during mouth opening is limited with a mean maximum gape angle of 112.8°. Each bite is relatively fast and is characterized by a quick nip at algal filaments, usually followed by a sidewads flick of the head. The jaws bear several broad multidenticulate teeth. It appears that these teeth engage turf algal strands which are either sheared during mouth closure or torn off as the head flicks sideways. InC. striatus, the jaw bones are considerably lighter than those ofA. nigrofuscus. There is much greater movement of the elements during mouth opening, resulting in a mean maximum gape angle of 177.6°. Each bite is slower than inA. nigrofuscus and is characterized by a wide gape as the mouth is applied to the substratum followed by a quick, upward flick of the lower jaw, with no sideways flick of the head. The jaws bear numerous elongate flexible teeth, with expanded incurved denticulate tips; those on the dentary often possessing a pointed blade-like process. It appears that these teeth brush particulate and epiphytic material from the surface of the turf algal strands and other substrata. These observations demonstrate howA. nigrofuscus andC. striatus are able to remove microalgae and detritus, respectively, from the same substratum. The results also demonstrate how relatively small differences in morphology can have a profound influence on the feeding abilities and trophic ecology of fishes.     

Reproductive biology and spawning habitat supplementation of the relict darter, Etheostoma chienense, a federally endangered species

We investigated the reproductive biology of Etheostoma chienense in the Bayou du Chien drainage of western Kentucky. Etheostoma chienense is similar in its ecology and reproductive biology to other members of the E. squamiceps complex. However, E. chienense is opportunistic in its choice of egg deposition substrates, as nests were found on a variety of natural and anthropogenic items. Due to an apparent lack of suitable spawning substrates, we added half-cylindrical ceramic tiles to several stretches of stream to increase potential nest productivity. Egg-clutches attached to artificial substrates were twice the size of egg clutches attached to naturally occurring materials. Laboratory experiments were conducted to determine nest rock size and mate choice preferences. Both the size of the male and of the nest rock appeared to be important parameters to spawning females. The life history information gathered here has significant management implications. Artificial spawning substrates should be placed in appropriate microhabitats (i.e., shallow, low-flow reaches in headwaters). Nest cavity vertical height should be about 3.0 cm and tiles should be spaced at least 0.5 m apart. We feel the use of surrogates (e.g., E. oophlyax) to investigate other types of spawning cover, and restoration of riparian buffer zones among other actions, would particularly benefit recovery efforts for this endangered species.     

Factors Affecting Redd Site Selection, Hatching, and Emergence of Brook Charr, Salvelinus Fontinalis, in an Artificially Enhanced Site

We measured microhabitat characteristics, hatching and emergence success of brook charr, Salvelinus fontinalis, in a series of sites selected and not selected by individuals spawning in an artificially enhanced lake outlet. Differences between the physico-chemistry of surface and interstitial water were small and did not suggest the presence of groundwater seepage. The mean surface water velocity was significantly higher in selected than non-selected sites during the incubation and emergence periods. Differences in interstitial water flow were not detected. Overall, selected substrate was coarser and contained a lower proportion of fine particles than non-selected substrate, as determined by the geometric mean diameter of particles, the proportion of fine particles (<1mm), and the Fredle index. The proportion of fine particles was correlated with sediment loading in incubators. A two-way ANOVA showed no significant effect of sites (selected versus non-selected) but did show a significant effect of the incubation substrate (Astro-turf, selected substrate, non-selected substrate) on both the hatching and emergence success; the percentages of hatching and emergence were significantly higher in Astro-turf than in non-selected substrate, with selected substrate being intermediate. The results of this study suggest that redd site selection by brook charr is based on surface water velocity and substrate characteristics (granulometry and proportion of fine particles) that in turn affect egg survival. It is possible that the lower proportion of fine particles in selected sites (and incubators) is related to their higher water velocity, which could carry away fine particles that reduce the availability of oxygenated water to the embryos. In the same way, higher water velocity could act as a proximate cue in the absence of groundwater seepage or interstitial water flow for individuals to select suitable sites for spawning and egg incubation.     

Evaluation of a conservation strategy: a spawning aggregation closure for red hind, Epinephelus guttatus, in the U.S. Virgin Islands

Many tropical reef fishes spawn in large aggregations, which are readily targeted by fishers. By the 1980s, at least two grouper spawning aggregations were eliminated by intensive fishing off the island of St. Thomas, U.S. Virgin Islands, and another aggregating species, red hind, was intensively targeted. By 1988, the average length of red hind had greatly decreased to 295 mm, and the sex ratio was extremely skewed to 15 females per male, suggesting a heavily fished stock. Since this species is a protogynous hermaphrodite, the loss of large individuals (primarily males) could potentially result in sperm limitation in spawning aggregations. In 1990, a spawning aggregation closure was implemented. By 1997, average size of red hind had increased to 395 mm and sex ratio had shifted to 4 females per male. Fish were observed aggregating only in structurally complex habitat along the insular shelf edge. This habitat type is apparently not common along most of the shelf edge off St. Thomas and may provide shelter while reducing risk of predation during aggregation periods. These data suggest that protection of spawning aggregations is a sound management strategy with considerable potential for aiding the sustainable use of reef fish resources.     

西沙群岛主要岛礁鱼类物种多样性及其群落格局

为了解珊瑚礁海域鱼类物种多样性及其群落特征,作者2003年5月在西沙群岛7座主要岛礁(北礁、华光礁、金银岛、东岛、浪花礁、玉琢礁和永兴岛)采用底层刺网进行了调查,运用聚类分析和非度量多维标度(NMDS)等多元统计分析方法,对7个岛礁鱼类的种类组成、优势种、多样性和群落格局进行了分析.调查海域共记录鱼类146种,隶属10...     

Evidence of density-independent mortality in a settling coral reef damselfish, Chromis viridis

To know if the variation in the number of settling fish larvae can be dampened by density-dependent postsettlement mortality, we investigated the relationship between settler density and predator-induced mortality of a coral reef damselfish, Chromis viridis. Totals of 2, 3, 5, 8, 10, 12, 14, 16, 18, and 20 fish of 10 or 20 mm total length were released in experimental cages enclosing a coral head of Porites rus (to provide settlement habitat) and five predators. The results showed that the mortality rate of both 10- and 20-mm fish was density independent.     

Components of fertilization success in the bluehead wrasse, Thalassoma bifasciatum

In many species of marine organisms, males and females releasegametes directly into the water column. Although free-spawningmarine invertebrates appear to have highly variable fertilizationsuccess, in tropical reef fishes the average fertilizationsuccess is quite high, typically over 90%; nevertheless, substantialvariation has been reported, and fertilization has a directeffect on fitness. We investigated the factors affecting fertilization success in natural spawnings of the bluehead wrasse, Thalassoma bifasciatum. During a two-year study at a site in St. Croix,we found extensive and predictable variation in fertilizationsuccess in pair spawns of this reef fish. Fertilization successaveraged 95%, but was affected by the amount of sperm released,the water velocity at a site, the mating success of the male,and the size of the female. As sperm released in a spawn increases, and as water velocity at a site decreases, sperm concentrationsshould remain higher in the vicinity of eggs for a longer periodof time, and both of these factors are correlated with increasingfertilization success. The recent history of individuals withpartners or sites did not affect the fertilization successof their spawn. In an evolutionary context, the real and predictable variance in fertilization success in this species may influencethe mating choices of males and females. However, there iscurrently no evidence that females use differences in fertilizationsuccess among males or sites in their reproductive decisions.     

Environmental Biology of an Endemic Cyprinid,Varicorhinus alticorpus,in a Subtropical Mountain Stream of Taiwan

An endemic freshwater fish, Varicorhinus alticorpus, was studied from 1990 to 1993 in a fast flowing mountain stream in southern Taiwan (22°30'N, 120°30'E). The analysis of environmental conditions suggested that the fish could tolerate water temperatures between 19–24°C, a pH of 8.0–8.8, and flow velocity from 20–100cmsec^–1. The fish occupied riffles and pools. They foraged and schooled during daytime and aggregated in crevices between rocks at night. Most juveniles stayed at the shallow sandy-pebble flat by the pool where flow was slow. The species feed primarily on the periphyton growing on the rocks, and leave unique scars after grazing. One peak of juvenile recruitment was observed right after the rainy season, suggesting that reproduction of the fish has adapted to the climate. The change of abundance of adults along the habitats (at 150 to 800 m altitude) also indicated that the fish might migrate to low altitudes for spawning and disperse back to higher altitudes for exploiting new resources. The environmental biology of this fish shows an example of a cyprinid adapted to habitats in a subtropical mountain stream.