Home range estimates for squaretail coralgrouper, Plectropomus areolatus (Rüppell 1830)

The aim of the study was to estimate home range areas and distance of movement away from a squaretail coralgrouper (Plectropomus areolatus) spawning aggregation site located within a small-scale 1.5 km² Marine Protected Area (MPA) in Pohnpei, Micronesia. Fifteen P. areolatus were acoustically tagged and re-located within a ca. 50 km² search area over a 4-month period that included reproductive and non-reproductive months. All relocated fish were found in areas of moderate to high coral cover either on the fore reef or inside the lagoon in home ranges of 0.048 ± 0.018 km² (μ ± S.E.). Variability in home range area (0.004–0.12 km²) and distance of movement from aggregation sites following spawning (0.02–23.0 km; 5.3 ± 3.6 km, μ ± S.E.) was observed, but did not appear to be sex specific. Five of the six relocated individuals were found within 0.02–6.1 km of the aggregation. This evidence and that from recent tag-recapture studies of epinephelids suggest that a substantial proportion of individual P. areolatus spawning populations reside within close proximity to their respective aggregation sites. Reproductive populations could be protected by MPAs of moderate scale (10 s of km²) that include aggregation sites, migratory corridors and adjacent home range habitats.     

Seasonal distribution and some features of the biology of spiny lumpfish <Emphasis Type="Italic">Eumicrotremus asperrimus</Emphasis> (Cyclopteridae,Scorpaeniformes) in the northwestern part of the Sea of Japan

According to data of 1981–2007, it was shown that the migration of spiny lumpfish Eumicrotremus asperrimus from wintering grounds to the coast begins in spring, with the onset of water warming. During summer and autumn, E. asperrinus feeds, concentrating in the bathymetric range of 100–300 m. With the start of winter water cooling, it migrates for wintering to depths larger than 500 m. Main aggregations of E. asperrimus were found off the coasts of Northern Primorye. Catches included specimens with a length of 3–16 cm; however, the overwhelming majority (95%) had a length of 5–10 cm, with the domination of two size groups: 6–7 and 9 cm. The spawning of E. asperrimus is apparently highly extended in time and occurs in the spring-summer period in shallow waters. Similarly to other representatives of the genus Eumicrotremus, E. asperrimus is a planktonphage with a narrow food specialization. Off the coasts of Primorye, in the summer period it feeds almost on one species—hyperiid Themisto japonica—with a value of diurnal diet averaging 6.7% of the body weight. According to an expert estimate, the biomass of E. asperrimus in the northwestern part of the Sea of Japan may comprise no less than 5000 t.     

Spawning aggregations of three protogynous groupers in the southern Gulf of Mexico

Spawning aggregations of red hind Epinephelus guttatus, tiger grouper Mycteroperca tigris and yellowfin grouper Mycteroperca venenosa were identified at two coral‐reef systems: Arrecife Alacranes (emergent bank reef) and Bajos del Norte (submerged bank reef) on the continental shelf of the Yucatan Peninsula (Campeche Bank), Mexico. At both reefs, E. guttatus forms large spawning aggregations between February and March. At Bajos del Norte, M. tigris reproduces in a small, low‐density aggregation in May, while M. venenosa aggregates at high densities for spawning between March and May. Multi‐species use of an aggregation site by E. guttatus and M. venenosa was observed at Bajos del Norte. The identified spawning aggregations are apparently stable in location over time, and all three species were commonly observed to spawn within 1 week following the full moon. Development and survival of the larvae spawned in these aggregations are probably aided by a seasonal (spring–summer) upwelling in the north‐east Campeche Bank. A permanent area closure at Bajos del Norte, currently outside any specific fisheries management area or regulations, would provide protection needed for the spawning aggregations of these three species.     

Observations of spawning in the Leather Bass, <Emphasis Type="Italic">Dermatolepis dermatolepis</Emphasis> (Teleostei: Epinephelidae), at Cocos Island,Costa Rica

Courtship and spawning behavior is described for the Leather Bass, Dermatolepis dermatolepis, from observations made from a manned submersible at Cocos Island, Costa Rica on 19 days between November 2006 and February 2007. Spawning occurred in the evening (16:00–18:30 h) in subgroups of 10–32 individuals that formed within aggregations of 50–70 individuals. The mating sequence was characterized by subgroup formation and crowding behavior followed by a brief vertical spawning rush, gamete release, and the rapid separation of participants. The aggregation was present on all dives, and spawning was not restricted to specific lunar phases.     

Spatial,temporal, and environmental dynamics of a multi-species epinephelid spawning aggregation in Pohnpei,Micronesia

Long-term and short-term underwater visual censuses using SCUBA, technical Nitrox, and closed circuit rebreathers (CCR) were carried out in Pohnpei, Micronesia, to define spatial and temporal dynamics within a semi-protected multi-species epinephelid (fish) spawning aggregation (FSA) of brown-marbled grouper, Epinephelus fuscoguttatus, camouflage grouper, Epinephelus polyphekadion, and squaretail coralgrouper, Plectropomus areolatus. Results identified species-specific patterns of habitat use, abundance, residency, and dispersal of FSAs. Fish spawning aggregations formed and dispersed monthly within a 21–160-d period after winter solstice within adjacent yet distinct outer reef habitats. The reproductive season coincided with periods of seasonally low sub-surface seawater temperature. Peaks in density varied among species both within the calendar year and relative to the winter solstice. Significant long-term declines in FSA density were observed for all three species, suggesting population-level fishery-induced impacts, similar to those previously reported for E. polyphekadion. Differences in density estimates were also observed between dive gear, with a threefold difference in densities measured by CCR for E. polyphekadion versus SCUBA that suggest a disturbance effect from exhaled SCUBA bubbles for this species. CCR also allowed surveys to be conducted over a larger area in a single dive, thereby improving the potential to gauge actual abundance and density within FSAs. Based on these findings, a combination of long-term and intensive short-term monitoring strategies is recommended to fully characterize trends in seasonal abundance and habitat use for aggregating species at single or multi-species FSA sites. Inherent variations in the timing and distribution of species within FSA make fine-scale temporal management protocols less effective than blanket protective coverage of these species at (e.g., marine protected areas covering FSAs and adjacent migratory corridors) and away from (i.e., temporal sales and catch restrictions) FSA sites.     

New data on biology of the pearlfish <Emphasis Type="Italic">Maurolicus imperatorius</Emphasis> (Sternopthychidae) from the Emperor Seamount Chain

The pearlfish Maurolicus imperatorius occurs above seamounts of the Emperor Seamount Chain between 30°–40° N and 168°–176° E. It forms dense aggregations at the daytime in the upper mesopelagial above the ground and disperses in the dark period of the day in the surficial layer. Judged by maturation dynamics of gonads, the spawning of this species occurs from January until April with the maximum in March. Catches of this species are characterized by expressed seasonal dynamics of size composition. Juveniles appear in catches in the end of spring-the beginning of summer. The maximum recorded SL is 68 mm. Among large fish, females dominate. The part of females is maximum in winter and minimum in spring. The age of fish with AC 46–63 mm is 265–420 days. The growth rate is abruptly retarded at the fourth month of life when the length 40–45 mm is attained. Life duration of most fish does not exceed 1.5 years, though some specimens may attain the age of two years. It is supposed that the presence of another species—M. japonicus—on the Emperor Seamount Chain may result from passive transfer in the Kuroshio waters.     

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.     

The aggregation of polar cod (Boreogadus saida) in the deep Atlantic layer of ice-covered Amundsen Gulf (Beaufort Sea) in winter

During the Circumpolar Flaw Lead System Study (CFL, 2007–2008), large aggregations of polar cod were detected in winter in the Amundsen Gulf (Western Canadian Arctic) using the EK60 echosounder of the CCGS Amundsen research icebreaker. Biomass estimated over 10 months reached a maximum of 0.732 kg m⁻² in February. Aggregations were encountered only in the presence of an ice cover from December to April. The vertical extent of the aggregations was dictated by temperature and zooplankton prey distribution. In winter, polar cod generally occupied the relatively warm deep Atlantic Layer (>0°C), but a fraction of the densest aggregations occasionally followed zooplankton prey up into the cold Pacific Halocline (−1.6 to 0°C). The diel vertical migration of polar cod was precisely synchronized with the seasonally increasing photoperiod. Throughout winter, polar cod aggregations migrated to progressively deeper regions (from 220 to 550 m bottom depths) in response to increasing light intensity, presumably to avoid predation by visual predators such as the ringed seal. Comparing Amundsen Gulf and Franklin Bay indicates that the entrapment of polar cod in embayments during winter is an important mechanism to provide marine mammal predators with dense concentrations of their main prey within their diving range.     

Prediction and verification of possible reef‐fish spawning aggregation sites in Los Roques Archipelago National Park,Venezuela

This study attempts to predict and verify possible spawning aggregation sites and times in the Los Roques Archipelago National Park, Venezuela, based on physical reef characteristics and the knowledge of experienced local fishermen. Three possible aggregation sites were selected for monitoring based on satellite images, low‐cost bathymetric mapping and interviews with experienced local fishermen. Abundances and sizes of 18 species that are known to form reproductive aggregations were monitored at these sites using underwater visual census for 7 days after each full moon from February to August, 2007. While spawning events were not observed, possible indirect evidence of spawning aggregations was found for Lutjanus analis at Cayo Sal and Boca de Sebastopol, Lutjanus apodus at Cayo Sal, Lutjanus cyanopterus at Cayo Sal and Piedra La Guasa and Epinephelus guttatus at Bajo California and Cayo de Agua. Additionally, indirect evidence was identified for the past existence of a spawning aggregation of Epinephelus striatus in the northern part of the archipelago, which may have been eliminated by overfishing c.15 years ago. Bathymetric mapping showed that the shelf edge at sites monitored in this study was shallower than at spawning aggregation sites in other parts of the Caribbean, and that sites were not proximal to deep water. While this study does not prove the existence or locations of spawning aggregations of reef fishes in the archipelago, it does add insight to a growing understanding of generalities in the relationship between seafloor characteristics and the locations of transient reef‐fish spawning aggregations in the Caribbean.     

Population dynamics of Japanese serow in relation to social organization and habitat conditions. II. Effects of clear-cutting and planted tree growth on Japanese serow populations

Population responses of Japanese serow (Capricornis crispus) to clear-cut logging and planted tree growth were studied by a direct count of the number observed in three areas, Takiyama (305 ha), Gentouziro (270 ha), and Tanokashira (324 ha), near Wakinosawa Village, Aomori Prefecture, Japan, during 1976–89. At Takiyama, a mature mixed forest ofThujopsis dolabrata var.hondai andFagus crenata decreased from 73 to 39% coverage of the area due to clear-cutting during 1978–83. The serow population maintained a relatively low stable density (3–6 individuals per km²) until 1985–87, and increased 5–10 years after the clear-cutting, reaching 9–10 km⁻² in 1988. At Gentouziro and Tanokashira, young plantations of Japanese cedar (Cryptomeria japonica) covered about half of each area. The population densities between 1980 and 1983 were relatively high (14–19 km⁻²), but declined thereafter, reaching 10–14 km⁻² in 1988–89. These results indicated that the density increase resulted from an improvement of food supply due to growth of scrub following the clear-cutting, and that the density decline resulted from a habitat change due to growth of planted Japanese cedar and a decrease in the food supply. In Wakinosawa Village, serow density began to increase 5–10 years after forest cutting, and the high population density, about three- or six-fold larger than that in mature forest, is expected to be maintained for about 20 years after logging.     

Reproduction of the wedge sole (<Emphasis Type="Italic">Dicologoglossa cuneata</Emphasis> Moreau) in captivity: spawning parameters and influence of the natural temperature

In this work, the wedge sole (Dicologoglossa cuneata) spawning under a natural thermocycle has been studied. The spawning parameters were similar to those of other flatfish in captivity, the relative fecundity being very high (1.7 ± 0.1 × 10⁶ eggs kg female⁻¹ per spawning season). The percentage of floating eggs decreased with time and was directly related to egg diameter, daily relative fecundity and fertilization rate. Nevertheless, the hatching rate variations were not correlated to any other spawning parameter. The temperature range during the spawning season was very wide (11–21°C) though the largest spawns occurred between 12 and 16°C. The natural temperature cycle influenced wedge sole egg production, the winter temperature minimum indicating the onset of spawning, but the variations in the reproductive season did not appear to affect the daily egg production. Future research should focus on the photoperiod and its interaction with temperature as key factor for spawning.     

Recruitment of stock of deepwater redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Scorpaeniformes,Scorpaenidae) in the pelagial of the Irminger Sea and adjacent waters

Results of comparative analysis of several ecologo-populational characteristics and fauna of parasites of deepwater redfish Sebastes mentella from the pelagial of the Irminger Sea and slopes of Greenland are provided. It was established that the nursery area of the species in this part of the northern Atlantic is located in the shelf and shallow-water sites of the Greenland slopes. Near the nursery area, at deepwater sites of the Greenland slope, aggregations of mainly immature specimens (68–86%) with an average length of 35–38 cm are located, and, in the oceanic pelagial, there are mainly mature specimens (91–95%) with a length of more than 30 cm. Considerable similarity and specific features of fauna of parasites of S. mentella from the southeastern slope of Greenland and the pelagial of the Irminger Sea indicate the belonging of fish aggregations in these areas to a single intraspecies group and the migration of maturing specimens from the slope to the pelagial. A conclusion is made that the aggregations of S. mentella in the pelagial of the Irminger and Labrador seas represent a pelagic ecological group formed by rapidly maturing specimens; a near-bottom ecological group at deepwater sites of the slope of Greenland is formed by slowly maturing specimens. No mass migration of the redfish from deepwater areas to shallow sites of the slope and to the oceanic pelagial of the northern Atlantic was recorded.     

Effective size,census size,and genetic monitoring of the endangered razorback sucker, <Emphasis Type="Italic">Xyrauchen texanus</Emphasis>

For the past several decades the Lake Mohave population of the federally endangered razorback sucker, Xyrauchen texanus, has had no natural recruitment because of intensive predation on larvae by non-native fishes. In response to impending extirpation, a repatriation program was implemented where larval razorbacks are collected from the wild following natural spawning, reared in protective custody, and then repatriated at a much larger size. In this study, we estimated annual (N _bf) and generational female effective size (N _ef) of the spawning stock by characterizing temporal genetic changes in mtDNA among larval cohorts, and then compared these estimates to the estimated number of reproductively capable (adult) females in Lake Mohave (N _f). Razorback suckers have life history and mortality schedules that could yield values of N _ef/N _f as low as 10⁻⁵ due to match–mismatch recruitment (or the “Hedgecock effect”) that increases variance in reproductive success. Average N _bf was estimated to be 160, N _ef was 706, and the ratio N _ef/N _f was 0.29 and 0.38 for arithmetic and harmonic mean N _f, respectively. Our findings indicate that (i) larval sampling in Lake Mohave sufficiently encompasses temporal and spatial variation within annual larval cohorts as to be representative of the spawning stock, (ii) roughly 3–16% (about 8% on average) of adult females contribute genetically to larval cohorts each year, and (iii) repatriated fishes appear to be contributing genetically to larval cohorts. Simultaneous genetic and demographic monitoring offers insights that neither approach can provide alone into effects of population decline and management practices in this species.     

Home ranges of raccoon dogs (<Emphasis Type="Italic">Nyctereutes procyonoides</Emphasis>, Gray, 1834) in Southern Brandenburg,Germany

The raccoon dog Nyctereutes procyonoides, a medium-sized canid, is a representative of the East Asian fauna and has been introduced to Europe during the years 1928–1953. Today, this alien carnivore is a widespread species in Eastern Europe, Finland and Germany. In our study, we determined home range sizes of raccoon dogs in an agricultural landscape in Northeast Germany between 2001 and 2004 by very high frequency radio tracking. Those data are useful for estimation of predator densities in respect to conservation of biodiversity and also to develop models for disease and parasite transmission. Yearly average home range sizes were calculated as 95% fixed kernel: 1.83 km² ± 1.54 and as 50% fixed kernel (=core areas): 0.50 km² ± 0.49. We documented seasonal differences in home range sizes as well as overlapping of home ranges from 0.65% up to 67%. Some individuals’ home ranges recorded during the same season showed a clear shifting between different years. Abandoned badger dens, located in the core areas of raccoon dogs home ranges, were important during the whole year and particularly used in the winter period. Therefore, distribution of those dens had some influence on the spatial distribution of raccoon dogs in the study area. Based on mean annual home range size, we estimated the mean local population density during winter as 1.1 individuals per square kilometre and during summer as 4.90 individuals per square kilometre.     

Some issues related to catches of northern Atka mackerel <Emphasis Type="Italic">Pleurogrammus monopterygius</Emphasis> (Scorpaeniformes: Hexagrammidae) in the near-surface water layer of the northern Kuril Islands

Studies performed in Pacific waters of the northern Kuril Islands from May to August 2003–2007 demonstrated that not only juveniles of Pleurogrammus monopterygius but also its adult specimens are found in the near-surface layer. Some adult fish migrate to the near-surface layer for feeding, while occurrence in this layer for other specimens is related to the change of spawning grounds. Among specimens with a length of 36–48 cm, females comprise 86.2%; among specimens with a length of 22–28 cm, females comprise 56%. Migrations in the near-surface layer have no mass pattern.     

Temporal dynamics of production and ingestion of the dominant mayflies in a subtropical stream in China

We investigated temporal dynamics of secondary production and trophic basis for four dominant mayfly species in a second-order river of the Hanjiang River basin in Middle China from June 2003 to June 2004. The secondary production of the dominant four mayfly species, comprising nearly 90% of the total density of mayflies, was 14.45 g m⁻²  per year for Ephemera sp., 9.15 g m⁻²  per year for E. sinensis, 7.23 g m⁻²  per year for Leptophlebia sp. and 1.55 g m⁻² per year for C. nigropunctata. C. nigropunctata and Ephemera sp. had most of their production in winter (from January to March), while E. sinensis and Leptophlebia sp. produced in two intervals, from June to September (summer) and from December of the first year to March of the next year (winter). Overlap in temporal distribution of production among the four mayflies was generally high (>0.60), especially those of C. nigropunctata, Ephemera sp. and Leptophlebia sp. Overlap of Leptophlebia sp. and Ephemera sp. was >0.85. Patterns of the four food types (amorphous detritus, vascular plant detritus, fungi, and diatoms) for each mayfly varied significantly (P < 0.01) over time, and patterns of food ingestion between the four mayflies were also significantly different (P < 0.05–0.01). Among the four main food types, all mayflies used amorphous detritus the most, which constituted 53–96% of their diets and contributed 54–97% to their production. Thus, temporal changes in the food web for mayflies in Heizhuchong stream are quantitative rather than qualitative.     

Historical and contemporary evidence of a mutton snapper (<Emphasis Type="Italic">Lutjanus analis</Emphasis> Cuvier, 1828) spawning aggregation fishery in decline

Scientific information on reef fish spawning aggregation fisheries is sparse in light of numerous regional declines and extirpations from overexploitation. Fisher interviews of the small-scale commercial mutton snapper (Lutjanus analis) spawning aggregation fishery at Gladden Spit, Belize, suggests a historic decadal decline. The reported trend is supported by analysis of inter-seasonal catch and effort and yield (2000–2002) that reveals a 59% decline in catch per unit effort (CPUE) and a 22% decrease in mean landings per boat. Declining population-level trends are also supported by a significant decrease in inter-annual median lengths of mutton snappers (2000–2006). These findings demonstrate the need for additional life history information that includes length-associated age and details on growth to provide clearer support of the effects on, and responses by, populations following fishing. In view of the historical changes to mutton snapper CPUE and landings at Gladden Spit and the fishery-associated declines in fish spawning aggregations observed globally, a precautionary approach to spawning aggregation management is warranted that provides full protection from fishing to enhance population persistence. The findings also highlight the need for substantially greater enforcement and long-term fisheries monitoring under a comprehensive regional management strategy.     

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.     

Coexistence of congeneric spiny lobsters on coral reefs: differences in conspecific aggregation patterns and their potential antipredator benefits

Den sharing by conspecific spiny lobsters (aggregation) is modulated by chemical attraction but may confer several, not necessarily mutually exclusive, antipredator byproduct benefits: a “guide effect”, which only benefits the individual attracted to a sheltered conspecific; a “dilution effect”, which reduces per-capita risk of predation simply through aggregation; or active “group defense”. Each potential benefit has a different set of predictors (relationships between aggregation and conspecific or predator densities), but conflicting results could suggest the simultaneous operation of more than one benefit. These predictions were tested for coexisting Panulirus guttatus (a reef-obligate) and Panulirus argus (a temporary reef-dweller) using data collected during 11 surveys on fixed sites over a coral reef in Mexico. P. guttatus greatly outnumbered P. argus, but P. argus showed a greater tendency to aggregate. All three benefits of den sharing operated for the more social P. argus, with “group defense” being of the most benefit for larger individuals, and the “guide” and “dilution” effects for smaller individuals recently immigrating into the reef habitat and sharing dens with larger conspecifics. P. guttatus did not display “group defense” and its aggregations appeared to be modulated by the interplay between attraction and aggressive behaviors. This species relied more on solitary crypticity, especially at larger sizes, but appeared to benefit from a “guide effect” at high conspecific densities. In experimental tanks, each species tended to aggregate when tested separately, but when tested jointly, aggregation among P. guttatus was significantly reduced. The experimental results reflect the differential patterns of aggregation between the fore-reef, where P. guttatus dominated, and the back-reef, where coexistence of both species was greater.