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.     

Two new gonad-infecting philometrids (Nematoda: Philometridae) from the yellowedge grouper Hyporthodus flavolimbatus (Serranidae) and the great northern tilefish Lopholatilus chamaeleonticeps (Malacanthidae) in the northern Gulf of Mexico

Based on light and scanning electron microscopical studies, two new gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) are described from marine perciform fishes in the northern Gulf of Mexico: P. hyporthodi n. sp. from the ovary of the yellowedge grouper Hyporthodus flavolimbatus (Poey) (Serranidae) and P. lopholatili n. sp. from the ovary of the great northern tilefish Lopholatilus chamaeleonticeps Goode & Bean (Malacanthidae). Philometra hyporthodi is mainly characterised by the body length of both the males (3.62–4.07 mm) and gravid female (105 mm), the length of the spicules (135–138 μm) and the presence of dorsal transverse lamella-like structures on the distal portion of the gubernaculum. Philometra lopholatili is distinguished by the presence of a distinct dorsal protuberance consisting of two dorsolateral lamellated parts separated from each other by a smooth median field, an uninterrupted mound on the male caudal extremity, the length of the spicules (165–189 μm) and the body length of the males (2.19–2.34 mm) and gravid female (280 mm). Philometra lopholatili is the first representative of the genus and the second philometrid species reported from fishes of the family Malacanthidae.     

Fish assemblage structure on a drowned barrier island in the northwestern Gulf of Mexico

We investigated the assemblage structure of fishes associated with different habitats (inshore mud, shell bank, and offshore mud) over a drowned barrier island, Freeport Rocks Bathymetric High, on the inner continental shelf of the northwestern Gulf of Mexico (NW Gulf). Density data from otter trawls were used to examine spatial (habitat and site) and temporal differences in fish assemblage structure using multi- and univariate procedures. Eight species accounted for 69% of the total composition and in order of decreasing abundance included shoal flounder (Syacium gunteri), dwarf sand perch (Diplectrum bivittatum), red snapper (Lutjanus campechanus), least puffer (Sphoeroides parvus), silver seatrout (Cynoscion nothus), largescale lizardfish (Saurida brasiliensis), silver jenny (Eucinostomus gula), and sand seatrout (Cynoscion arenarius). Multivariate results indicated fish assemblage structure differed among habitats (ANOSIM; Global R = 0.190, P < 0.001) and survey dates (ANOSIM; Global R = 0.541, P < 0.001); however, differences among sites were negligible (ANOSIM; Global R = −0.015, P = 0.749). Highest densities of dwarf sand perch and least puffer were found on the shell bank, while densities of shoal flounder, largescale lizardfish, and silver jenny were highest on offshore mud. In addition, smallest sizes and highest densities of six of the eight abundant species were found in July, suggesting an important period for juvenile fishes. Diversity indices also varied relative to habitat with highest Shannon diversity (H′) and species richness (S) values for fishes associated with the shell bank. Results of this study highlight the importance of a mosaic of habitat types to fish assemblages on a drowned barrier island in the NW Gulf. Handling editor: I. Nagelkerken     

Preliminary observations on the life history of the white-streaked grouper, <Emphasis Type="Italic">Epinephelus ongus</Emphasis>, from Okinawa,Japan

A preliminary analysis of 175 specimens of the white-streaked grouper, Epinephelus ongus (Serranidae), was undertaken to determine life history characteristics of the species. Sagittal otoliths, stomachs, and a subsample of gonads were removed to determine age at length, diet, and reproductive strategy. The von Bertalanffy growth equation was used to describe growth in this species and yielded the growth parameters L^∞ = 438.3, K = 0.04334, and t₀ = −8.752. Fish ranged in age from 1 to 20 years. Diet was consistent with other serranid species and included crabs, shrimps, octopi, and fishes. Based on a very limited number of specimens (n = 12), the larger size and older age of males compared to females suggests that E. ongus may be a protogynous hermaphrodite.     

Cleaning by the wrasse Thalassoma noronhanum, with two records of predation by its grouper client Cephalopholis fulva

The Noronha wrasse Thalassoma noronhanum was recorded cleaning 19 client fish species at Fernando de Noronha Archipelago, o. north–eastern Brazil. The preferred clients were non–dangerous, mostly planktivorous species, whereas the potentially dangerous, predatory species were rarely cleaned. T. noronhanum acts as a cleaner in two distinct ecological situations, at and outside the cleaning stations, and attends different client species in each of them. Potentially dangerous clients were mostly attended outside the cleaning stations. Many attacks and two instances of predation on the cleaner wrasse by the grouper client Cephalopholis fulva were recorded. The attacks occurred on individual wrasses foraging near the bottom outside the cleaning stations.     

Reproductive behavior of the halfmoon grouper, <Emphasis Type="Italic">Epinephelus rivulatus</Emphasis>, at Ningaloo Reef,Western Australia

Behaviors associated with spawning by the halfmoon grouper, Epinephelus rivulatus, at Ningaloo Reef, Western Australia, are described from in situ observations made each evening throughout most of a lunar cycle. Spawning occurred after sunset on six consecutive evenings during the full moon period. During this time males were particularly aggressive toward one another and maintained high levels of activity among the gravid females that rested within each of their territories. Spawning occurred when a male swam alongside a responsive female and the pair rose in a tight spiral 1–1.5 m into the water column before releasing gametes and returning to the seabed. Spawning activity was followed by a longer nonspawning period (ca. 20 days), when fewer intraspecific interactions were observed and gamete reserves were replenished. Histological and behavioral evidence suggests that this cycle of spawning and replenishment may occur on a monthly basis. Although individual fish, particularly females, moved into certain areas to spawn, E. rivulatus did not form spawning aggregations as do larger species of grouper.     

Resource partitioning by ungulates on the Isle of Rhum

Summary This paper describes the seasonal changes in vegetation community use by red deer, cattle, goats and ponies on the Isle of Rhum, Scotland. During the winter, when food resources were of low abundance and digestibility, the ungulates showed extensive resource partitioning. During the summer, when resource availability and digestibility was high, the grazing species, red deer, cattle and ponies congregated on the vegetation communities which contained high biomasses of a high quality resource, mesotrophic graminoids and forbs. Goats, with a digestive system adapted to dealing with browse, foraged primarily on the communities dominated by dwarf shrubs. The patterns of resource use in this group of ungulates are discussed in relation to competition; species had relatively exclusive esource use during periods of low food availability during tye winter and had a high degree of resource use overlap when food was abundant during the summer. This suggests that there was little competition for food during the summer and that exploitative competition for the high quality foods led to resource partitioning during the winter. Senarios are described which predict the pattern of resource use between two species (one competitively superior to the other on the preferred resource) utilizing mutually or exclusively preferred resources. A model developed by Illius and Gordon (1987), based on the allometry of metabolic requirements and bite size, is used to provide a mechanistic explanation for the observation that the red deer were able to exploit the high quality plant communities during the winter, whereas the cattle moved off to feed on poorer quality communities at this time.     

神农架自然保护区川金丝猴食源植物的分布和丰富度

温带地区分布的灵长类动物在食物匮乏的时候容易受到食物不足的胁迫。川金丝猴就是分布于温带区域的灵长类动物之一,因此在不同的季节,食物对其有不同程度的影响。神农架自然保护区是川金丝猴分布的最东缘,该地区的研究对川金丝猴的保护有着非常重要的影响。本文通过对神农架川金丝猴食源植物和栖息环境 的植被调查,来探讨食物的分布和丰富程度对川金丝猴的影响。在神农架川金丝猴分布的核心地区,选择具有代表性的植被类型,按照海拔梯度设置88个样方,基于优势树种和数据分析,我们把川金丝猴的栖息地划分为12 个类型。阔叶林的食源植物种类要高于针阔混交林;而低海拔的类型中提供食源植物的种类要高于高海拔类型。尽管川金丝猴的食谱范围很广,但是它喜食的食物种类分布极不均匀,而且在其不同类型的栖息地内,食源植物的种类和数量随着季节的变化而变化。因此,季节的变化和食源植物的分布不均衡都会影响川金丝猴的取食行为和时间分配。我们建议借助人为改造森林结构,增加食源植物的数量,进而达到保护和扩大川金丝猴种群的目的。     

Reproductive biology and implications for management of the orange-spotted grouper Epinephelus coioides in the southern Arabian Gulf

The reproductive biology of Epinephelus coioides was determined from the examination of 1455 individuals collected between July 2005 and June 2007 in the southern Arabian Gulf. Histological preparations of gonads indicated that males were either derived from a juvenile phase or the transition of postspawning females, confirming a diandric protogynous sexual pattern. The spawning season was well defined, occurring once a year during April and early May. Peaks in spawning occurred after the full and new moons and was completed within a single lunar cycle. The presence of mature males over the entire size and age range and the absence of inactive mature females during the spawning season suggested that the population was not constrained by sperm limitation. While specimens undergoing sexual transition were only observed in size and age ranges of 335–685 mm total length ( L _T) and 5–6 years, patterns in the proportion of males in size and age classes suggested that sex change occurred at a relatively constant rate after female maturation up to the maximum size (1002 mm L _T) and age (11 years). Relationships between reproductive output and capacity with size and age indicated that conventional regulations that equate the mean size at first capture to sexual maturation are unsuitable for the management of E. coioides . The maximum age, small size and young age at sexual maturation ( L _min= 320 mm L _T, 2 years, for females and 242 mm L _T, 1 year, for males) conflict with the general pattern for large epinepheline groupers and may be a direct result of the intensive demersal fishery in the southern Arabian Gulf.     

The Influence of Habitat Complexity on Reef Fish Communities in the Northeastern Gulf of Mexico

Several previous studies have attempted to correlate habitat complexity and reef fish species diversity. These studies have mostly examined natural reef systems, but results differed. To examine this relation, we built 1 m² habitats with 20 replicates of five complexity levels from July to August 2001 in the northeastern Gulf of Mexico (n=100). In June and July 2002, we built new habitats using the 2001 design, but also added a sixth complexity level (n=120). In order of increasing complexity these included: cage, shell, cage-shell, block-shell, cage-block-shell, and shell-block-pyramid habitats. Most fish in both years were juveniles and included species common to reef structures in the northeastern Gulf of Mexico. In 2001, we identified 26 fish species, and the dominant species was red snapper, Lutjanus campechanus (41%), followed by rock sea bass, Centropristis philadelphica (23%), and sand perch, Diplectrum spp. (14%). In 2002 we identified 36 species, and the dominant species was tomtate, Haemulon aurolineatum (36%), followed by Diplectrum spp. (19%), and L. campechanus (13%). In 2001, species diversity and richness were significantly (P<0.05) higher on more complex habitats (H′=1.7, S=11–12) compared to less complex habitats (H′=0.8–1.0, S=4–9). In 2002, patterns among diversity, richness and reef complexity were less apparent with only the least complex habitats shell and cage showing significantly lower values. In both years, multidimensional scaling grouped by complexity levels with cage and shell habitats showing the clearest separation from other habitat types. Also, with few exceptions (only 8%) analysis of similarities showed significant (P<0.05) differences in fish communities across complexity levels. Although community composition varied between years, this study provided evidence to support the hypothesis that habitat complexity increased reef fish species diversity.     

Differential utilization of space and food by the inshore rockfishes (Scorpaenidae: Sebastes) of Carmel Bay,California

Synopsis Six rockfish species were found to be common in the Carmel Bay kelp forests. Five of these occupy spatial zones that are more or less distinct from one another. Three species (S. atrovirens, S. chrysomelas, and S. carnatus) occupy species-specific spatial zones while two others (S. serranoides and S. melanops), although spatially distinct from each other, occupy zones that overlap completely with a sixth species, S. mystinus. Food overlap values (PSI) indicate that S. mystinus has low competitive overlap with all other species, and hence can coexist with two species using the same habitat. Dietary arrays reflect the distinct spatial zones occupied by most of the rockfishes. Structural characteristics associated with feeding (maxillary, intestine, and gill raker length) suggest that these species are differentially adapted in regard to feeding morphology. The coexistence of these rockfishes appears to be the result of the partitioning of food and space resources, rather than the result of stochastic events which appear to be important in the structuring of some coral-reef fish communities. S. mystinus juveniles represent a major trophic link between adult piscivores and the planktonic organisms upon which the juveniles feed. A sustained crash in S. mystinus numbers might have a negative effect on abundance of kelp forest piscivorous species.     

Age specific food utilization and spatial distribution of the puffer,Takifugu niphobles, over an intertidal sand flat

Synopsis Spatial distribution and feeding habits of the puffer fish,Takifugu niphobles, were studied to understand its mode of resource utilization in an intertidal sand flat at Tomioka in the western coast of Kyushu Island, Japan. The transect survey during high tides showed the presence of young puffers near the shoreline, while adults were mainly found in the offshore area of the sand flat. The gut contents analysis showed that although the young puffers foraged more frequently on organisms dwelling in the inshore area than the adults, both puffers fed mainly on the ghost shrimpCallianassa japonica inhabiting the entire sand flat. There was no apparent difference in the size of consumedC. japonica between the young and adult puffers. However, comparison of size structures of ghost shrimps in the field and in the gut contents showed that the young puffers foraged both from inshore and offshore areas of the sand flat, while the adults foraged mainly in the offshore area. This suggests that young puffers move more frequently over the sand flat with tides than adult ones. This pattern of trophic separation among size classes may reflect environmental features of the intertidal sand flat with large tidal fluctuations.     

Distribution,relative abundance and size composition of the threatened serranid Epinephelus daemelii in New South Wales,Australia

The aim of this study was to undertake baseline surveys on the distribution, relative abundance and total lengths (L_T) of a threatened epinephelid species, black cod Epinephelus daemelii, in New South Wales (NSW), Australia, their westernmost distribution. Diving surveys at 83 sites where E. daemelii were expected to occur were undertaken from 2009 to 2011 using 45 min roving diver counts. Sites were spread through northern NSW, including Lord Howe Island (LHI). Individual fish were measured using stereo‐video, enabling accurate length measurement. Surveys were repeated at a sub‐set of sites to assess temporal variation across days, seasons and years. A total of 117 E. daemelii were recorded during baseline surveys, occurring at 42% of the surveyed sites. Across all surveys, the highest numbers recorded (14–18 individuals at a site) were at the outer Solitary Islands and Fish Rock (Smoky Cape). Fewer E. daemelii were found southwards, but two sites in the Port Stephens–Great Lakes Marine Park had consistent numbers (three to six) over four annual surveys. Only 12 E. daemelii were recorded from eight of the 18 sites at LHI. The numbers observed at re‐surveyed sites were generally stable over years. There were latitudinal and cross‐shelf differences in L_T. Individuals in the north were found to be significantly larger than those further south, and fish offshore were significantly larger than those inshore. The largest measured fish was 135 cm, smaller than the maximum L_T(c. 170 cm) recorded for this species. The smallest fish was 26 cm. Overall, it is considered that the abundance of E. daemelii is low compared to anecdotal data even though they have been protected for c. 30 years in NSW. These findings provide an essential benchmark to assess ongoing status and response to protective management.     

Interpreting patterns of resource utilization: randomness and selectivity in pollen feeding by adult hoverflies

Summary Adult syrphid flies feed primarily on pollen and nectar from flowers and may be regarded as suitable models for the investigation of resource partitioning in a plant/pollinator system. The present study examines the extent to which a small group of six species are selective in their diets and investigates the role of flower colour as a means by which such selectivity may occur. Flower feeding preferences were determined by pollen analyses of gut contents and an extensive flower sampling programme was under-taken to provide information on the relative abundances of the food resources available to the insects. Flower colours were defined by their reflectance spectra, and the inherent colour preferences of the flies were determined by field experiments in which natural flowers were simulated using painted plastic discs. The results reveal that some hoverfly species are highly selective in their pollen diets, while others have a more generalist approach to their foraging. The division of flower resources by the more selective species is shown to be dependent, at least partially, on the colours of the flowers. The findings are discussed in relation to the theories of Competition and Optimal Foraging and the mechanistic approach to ecology. The use of learning models is suggested as an alternative means of investigating patterns of resource use in future research.     

Effects of flowering plant's patch size on species composition of pollinator communities,foraging strategies,and resource partitioning in bumblebees (Hymenoptera: Apidae)

Summary In 4 common Middle-European mainly bumblebee-pollinated plant species (Impatiens glandulifera, Echium vulgare, Aconitum napellus, Symphytum officinale) the influence of patch size on species composition of the pollinator community was studied. Short-tongued species were most dominant in large patches, while small patches were frequented by middle- and long-tongued bumblebees. This phenomenon was extremely obvious in Symphytum officinale and Aconitum napellus, where short-tongued species had bitten a hole in nearly every flower of large patches. Long-tongued species were forced to small patches, where nectarrobbing occurred only exceptionally. In small patches visitationrate (Number of visits per flower per hour) was not lower but either equal or even higher then in large patches. Nectar measurements in Echium vulgare showed, that not only the mean quantity of nectar but also the variance was lower in small patches. As a result, the possible gain can be predicted much more precisely in a small patch than in a large one, and bumblebees have less difficulties in making the right foraging decisions. According to this, foraging strategies depend on patch size. This was confirmed by a computer simulation. The conclusion can be drawn, that many bumblebee species are able to share the same resource by using different patch sizes. Since large flower patches occur mainly in man-made habitats, the dominance of short-tongued species in many bumblebee communities studied by other authors may be unnatural.Supported by the Landesgraduiertenförderung Baden-Württemberg     

Evidence for sexual dichromatisms in spawning aggregations of yellowfin grouper Mycteroperca venenosa and tiger grouper Mycteroperca tigris from the southern Gulf of Mexico

Colour pattern characteristics and gonad histology were used to detect sexual dichromatisms in yellowfin grouper Mycteroperca venenosa and tiger grouper Mycteroperca tigris from the Campeche Bank, Mexico. Specimens were obtained from commercial catches between March and May during 2002 and 2004. All specimens were examined dead. Ninety-seven per cent of males had different sex-associated colour patterns. Male yellowfin grouper displayed a bright yellow blotch on both sides of the lower jaw while females retained a reddish lower jaw. Male tiger grouper had uniform dark pectoral fins while females had bright orange pectoral fins. In situ observations of live fishes at fishing sites showed the lower jaw and pectoral fin colourations to be clearly visible underwater at a depth of 35 m. All males of both species and most females (80% yellowfin grouper and 98% tiger grouper) were sexually active and probably caught during their spawning season. This suggests that distinct colourations observed for male M. venenosa and M. tigris may be seasonal displays associated with spawning. Both the lower jaw and pectoral fin colourations were still visible in dead fishes after several days on ice. Differences observed for ray length of exserted vertical fins in tiger grouper specimens were probably not a sex-associated characteristic.     

Bathymetric distribution and diversity of deep water polychaetous annelids in the Sigsbee Basin, northwestern Gulf of Mexico

The deep water polychaete fauna is analyzed in this study particularly regarding its composition and variations with depth in the Sigsbee Basin, northwestern region of the Gulf of Mexico. Samples were taken at 10 stations along a bathymetric gradient with depth ranges from 200 to 3760 m with a USNEL (0.25 m²) corer. A total of 287 individuals were identified, from 21 families and 65 species. The most important families, both in terms of abundance and species richness, were: Paraonidae (65.4 ind./0.25 m², 9 spp.), Cirratulidae (28.93 ind./0.25 m², 7 spp.) and Spionidae (18.07 ind./0.25 m², 7 spp.). In general, density tended to decrease with depth with minima at around 2000 m, although two abundance peaks were detected at 3700 and 3760 m, making the pattern seem an inverted parabolic curve. The Shannon-Wiener diversity values varied from 0.54–0.92 at around 2000 m to 3.39 at 3620 m and 3.34 at 3760 m. These results contrast with what is already reported from the North Atlantic and the Tropical Pacific deep benthic communities, where highest diversities are found at 2000 m. Faunal changes evaluated through Beta Diversity (0.08–0.1) and the low similarity found between the stations, emphasized the high variability in the composition of the fauna in the Sigsee Basin, meaning that the faunal composition is practically different at all the sampling stations. Ten species are newly recorded for the Mexican fauna.     

Ecological studies of the nemertean fauna in an estuarine system of the northwestern Gulf of Mexico

The distribution and abundance of nemerteans in the brackish-water lakes of Sea Rim State Park, Texas, near the Louisiana border, were studied and compared with other macrobenthos during one year. Six of 93 macrobenthic species collected were nemerteans (0.9% of the total number of specimens). Only one species of nemertean, Carinoma sp., was consistently present. This species is the most ubiquitous and, probably, the most abundant nemertean in the estuarine systems of the Texas coast. Carinoma sp. was collected at Sea Rim from a salinity range of 0–21 ppt and at other Texas estuaries from 2–26 ppt. Preliminary experiments with Carinoma sp. as predator and as prey indicated that it feeds on polychaete worms and in turn is fed upon by white (Penaeus setiferus) and brown (P. aztecus) shrimp.     

Petroleum production platforms as sites for the expansion of ciguatera in the northwestern Gulf of Mexico

Ciguatera is a common human disease of tropical, coral reef ecosystems acquired by consuming finfish-containing ciguatoxins (CTX). There are few records of this disease in the northwestern Gulf of Mexico, a region characterized by soft muddy bottoms that are considered poor habitat for the CTX source dinoflagellate Gambierdiscus toxicus. However, the approximately 4000 petroleum production platforms and hundreds of state-sponsored artificial reefs located in the Gulf of Mexico provide hard substrate and often support coral and other components of the tropical benthos. In addition to their role in their resource extraction, these oil production platforms are also popular sites for recreational fishing and sport diving. We examined these platforms as potential substrate for G. toxicus and report a first record of this species in the NW Gulf of Mexico. All the platforms (n = 6) examined harbored the dinoflagellate as an epiphyte on the fouling community, with three finds of G. toxicus associated with the pelagic macroalga Sargassum. Only minor toxicity (<0.15 ppb) was noted in two of 20 great barracuda (Sphyraena barracuda) examined. Tagging data suggest trans-Gulf migrations by barracuda are common; thus, we cannot determine if the toxicity was acquired locally or transported in migrating fish.These platforms are a clear example of how human activity has altered the environment in a way that allows expansion of a HAB population. The rapid increase in production platforms since 1942 has provided novel substrate in a sandy/muddy bottom environment generally considered to be poor habitat for these benthic dinoflagellates. These platforms create a unique habitat in the upper euphotic zone and serve as intersection points for fishermen and potentially toxic fish. Many Gulf of Mexico states have active programs to turn non-producing platforms into artificial reefs. Our results suggest that the use of these platforms as fisheries enhancement structures could have unintended consequences for human health, particularly if projected rising sea-surface temperatures over the next century alter benthic distributions and fish migration patterns. These concerns also extend to mariculture operations around oil production rigs or offshore wind farms, both of which would also add substrate for epibenthic microalgae.