Life history and distribution of the small south-western Atlantic octopus, Octopus tehuelchus

Although this species has been reported from shallow waters down to 90 m depth, knowledge is almost entirely based on intertidal samples. In this study both intertidal and subtidal samples were taken during 1982–1987, in northern San Matias Gulf (41° S, 63° 30' W). This is a large-egged (eggs: 9–12 mm long ×–5 mm wide, stack of 4–6 mm long) and small-sized (up to 150 g) octopus. Egg laying occurs between autumn and winter. Embryonic development takes about four months (water temperature:–19°C). Large hatchlings (DML: 5·64 mm, TL: 14·23 mm, TW: 0·139 g) emerge over spring and early summer, and development is direct. Maximum size is reached after 17–18 months; mating takes place in summer. Females reduce their feeding activity when they reach maturity, and cease eating while brooding. Mean life-span is two years, but some individuals (mostly females) may live up to three years. Females approaching the beginning of the brooding period move to the subtidal zone, where males outnumber females until the end of summer and females (mostly brooders) then outnumber males. In the intertidal zone sex ratio was 1:1 from December to late March, but in April males outnumber females.
These life-history traits are compared with those of other large-egged octopuses and are discussed in relation to environmental conditions prevailing in the San Matias Gulf.     

Seasonal changes in serum glucose and condition of the plaice, Pleuronectes platessa L.

Monthly sampling of plaice caught off the north-east coast of Scotland between February 1983 and May 1984 revealed a seasonal increase in condition factor, hepatosomatic index and serum glucose, which appeared to be related to the period of active feeding. The spleen indices followed a similar seasonal increase, although this was not statistically significant, while the kidney indices showed little change over the 16 months. The peak for the gonadosomatic index was in February/March 1984, but among these plaice (aged 4–5 years) there were still large numbers of immature males and females and there was no increase in 1983. Apart from the hepatosomatic index for January 1984, there was no significant difference between male and female plaice.     

Reproductive biology of gag in the southern Gulf of Mexico

Aspects of the reproductive biology of gag Mycteroperca microlepis in the southern Gulf of Mexico were studied by following seasonal variations in the gonado‐somatic index and through histological examination of gonads. Gag were collected from inshore and offshore waters of the Campeche Bank, Yucatan, Mexico, between April 1996 and December 2001. This species is a protogynous hermaphrodite, and appeared to be depth‐size distributed. The smallest gag (9–49 cm L _F) collected were all juvenile females, and were caught in inshore waters (1–10 m depth), while the largest (49–116 cm L _F), mainly adult females, males and transitionals, were captured in offshore waters (33–167 m depth). Overall the offshore male to female ratio was female‐biased (1 : 3·3) and differed significantly from unity. The species spawns at depths of c . 50–53 m, from early winter to mid‐spring, with peak spawning activity occurring between January and March. Fifty per cent of females reached first maturity at 72·1 cm L _F. At 103 cm L _F, 50% of sampled females had changed into males. Gag can be considered a monandric species, and sexual transition for this grouper seemed to occur in fish distributed within a narrow size range (85–111 cm L _F). The results are compared with those of other authors for gag stocks from the south‐east Atlantic coast of the U.S.A. and the north‐east Gulf of Mexico.     

Dynamics of mate-searching behaviour in a hilltopping butterfly, Lasiommata megera (L.): the effects of weather and male density

By studying a hilltopping population of the satyrine Lasiommata megera in southern Sweden, the effects of density and meteorological conditions on mate-searching behaviour were investigated. Lasiommata megera males switched between stationary and vagrant behaviour, and the behaviour adopted was correlated to meteorological conditions; more males were stationary at low temperatures, low irradiation levels and high wind speeds than vice versa. Body temperature measurements indicated that these factors were important in deciding the body temperature and thereby the flight activity of males. Male density did not significantly influence mate-locating behaviour. The tendency of males to hilltop and their distribution around the hill were strongly influenced by weather. The hilltopping behaviour of this species did not adhere to an all-or-none pattern, but instead males, as well as the stations they used, were found at increasingly higher elevations on the hill with increasing temperatures and decreasing wind speeds. Moreover, males tended to use the lee side and sun-exposed side of the hill. Females, of which the majority were already mated, also showed this distribution around the hill, but preferred lower elevations than males. Release experiments did not reveal any propensity of mated females to fly uphill. Such a propensity was shown by released virgin females.     

Spatiotemporal variation in the population structure of the European hake in the NW Mediterranean

The bathymetric distribution of Merluccius merluccius was studied as a function of length, age and maturity of specimens caught by commercial trawl and longline in Different seasons. Males matured first at 28·8 cm (3 years old), and females at 38·0 cm (3·5 years old). Reproductive activity was noted practically throughout the year with its most pronounced spawning peak in the autumn. Most fish <37–40 cm were males and >46 cm were females. Specimens occurred between 50 and 750 m depth, although density was low at >400 m. Adults were found at all depth strata studied. Recruits and juveniles were limited to inshore waters <400 m, most were found between 100 and 200 m. Spring and summer were the preferred seasons for recruitment; although for both seasons there was some interannual variation. Adult distribution also varied, according to the season. Young adults were spread over the entire depth range, with the biggest ones concentrated at the edge of the shelf (150–350 m), especially in autumn and winter. The main spawning peak coincided with this concentration of adults suggesting that spawning occurred in autumn/winter at the edge of the shelf.     

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 movements of pikeperch in a shallow reservoir

The movements of 12 female (62–74 cm) and eight male pikeperch (55–64 cm) radiotagged in early March 1997 in the shallow and turbid Bygholm Reservoir, peaked during the summer, but all fish were also active during the winter. Females moved more than males and their activity was correlated with water temperature. Rate of movement was correlated positively with body size for both male and female pikeperch. During the breeding season (April–May) males became stationary for 14–47 days. Spawning sites, inferred from movements of males, were at depths of 2·0–2·5 m on hard substrata, mainly gravel in areas with many submerged trees and shrubs. Males tended to use the same spawning site the next year. Diel activity pattern varied seasonally but activity was highest from 1800 to 2400 hours.     

A lifetime at depth: vertical distribution of southern elephant seals in the water column

Although numerous studies have addressed the migration and dive behaviour of southern elephant seals (Mirounga leonina), questions remain about their habitat use in the marine environment. We report on the vertical use of the water column in the species and the potential lifetime implications for southern elephant seals from Marion Island. Long-term mark-resight data were used to complement vertical habitat use for 35 known individuals tagged with satellite-relay data loggers, resulting in cumulative depth use extrapolated for each individual over its estimated lifespan. Seals spent on average 77.59% of their lives diving at sea, 7.06% at the sea surface, and 15.35% hauled out on land. Some segregation was observed in maximum dive depths and depth use between male and female animals—males evidently being physiologically more capable of exploiting increased depths. Females and males spent 86.98 and 80.89% of their lives at sea, respectively. While at sea, all animals spent more time between 300 and 400 m depth, than any other depth category. Males and females spent comparable percentages of their lifetimes below 100 m depth (males: 65.54%; females: 68.92%), though males spent 8.98% of their lives at depths in excess of 700 m, compared to females’ 1.84% at such depths. Adult males often performed benthic dives in excess of 2,000 m, including the deepest known recorded dive of any air-breathing vertebrate (>2,133 m). Our results provide a close approximation of vertical habitat use by southern elephant seals, extrapolated over their lifespans, and we discuss some physiological and developmental implications of their variable depth use.     

Movements and diving of grey seal females (Halichoerus grypus) in the Gulf of St. Lawrence, Canada

Five female grey seals were tracked with satellite-linked time-depth recorders during September to April 1993-1994. Seals remained in the northern Gulf of St. Lawrence (Gulf) for 1-2.5 months after capture. Four females dove primarily to depths <10 m and 20-70 m, while all dives of the fifth female, a blind animal, were <10 m. During October/November, all animals moved into the southern Gulf or onto the Scotian Shelf. This migration lasted 6-10 days, during which time animals covered 350-800 km. During that migration, all females, including the blind animal, dove up to 100 m, but the majority of dives were to depths of 40-70 m. Two seals stayed in the southern Gulf through the winter while the others left the Gulf in January. When in the southern Gulf and on the Scotian Shelf, dive depths and bathymetry information indicated that dives were to the bottom.     

Age estimation, growth, maturity and distribution of the roundnose grenadier from the Rockall trough

This paper summarizes the history of commercial exploitation of roundnose grenadier Coryphaenoides rupestris in the North Atlantic. Length frequencies of C. rupestris in 1993, from 400 to 1200 m on the slopes of the Rockall trough indicate a reduction since the 1970s in the modal length of fish found at 700–1000 m. Ages ranged from 2 to 50 years for males and 2 to 60 years for females, with most between 10–38 years. Females attained a greater asymptotic pre-anus length ( L _∞=19.5 cm) than males ( L _∞=15.5 cm) and had a greater weight for a given age (male W _∞=761g, female W _∞=1132g). This species may have a protracted spawning period. Using pre-anus lengths, 50% of male fish were mature at 10 cm (ages 8–10) while 50% of female fish were mature at 12 cm (ages 9–11). At the greatest depths sampled the length frequency of fish was bimodal with a hiatus between 9 and 11 cm (ages 8–12). Highest catch rates occurred on the Donegal slope in September at a depth of 800–1000 m.     

Stress tolerance and burrowing behaviour in the southern African millipede Alloporus uncinates

Laboratory experiments were carried out to assess the tolerance and behaviour of the southern African spirostreptid millipede Alloporus uncinates (Attems) to moisture and temperature stress. Rates of water loss in dry air were 0–026 mg H₂0 cm^-2 hour^-1 for females and 0021 for males and remained relatively constant with an increase in temperature from 20 to 30°C but at higher temperatures there was a rapid increase in water loss, especially for females. In dry laboratory conditions at 30°C all individuals died within 30 days, whilst at 20°C at least 90% of individuals survived this period. Aggregation appeared to have no significant effect on survivorship but small body size conferred a survivorship advantage. Females burrowed earlier and to a greater depth than males, and initial moisture content of soil had a significant effect on mean burrow depth. Alloporus uncinatus , like other spirostreptid millipedes, appears to have considerable tolerance to dry conditions but the wide geographic and habitat range of this species may mean that the intensity of selection for tolerance to moisture stress may vary.     

中亚热带森林植物多样性增加导致细根生物量“超产”

细根在森林生态系统C分配和养分循环过程中发挥着重要作用, 但对地下细根与植物多样性之间关系的研究相对较少。该研究选择中亚热带从单一树种的杉木(Cunninghamia lanceolata)人工林到多树种的常绿阔叶林(青冈(Cyclobalanopsis glauca)-石栎(Lithocarpus glaber)林)的不同植物多样性梯度, 用根钻法采集细根并测定其生物量, 用Win-RHIZO 2005C根系分析系统测定细根形态参数, 以验证以下3个假设: 1)植物种类丰富度高的林分其细根生产存在“地下超产”现象; 2)根系空间生态位的分离水平是否随着植物多样性增多而增大? 3)细根是否通过形态可塑性对林木竞争做出响应?结果显示: 从单一树种的杉木人工林到植物种类较复杂的青冈-石栎常绿阔叶林, 0-30 cm土层的林分细根总生物量和活细根生物量均呈增加的趋势, 即细根总生物量为杉木林(305.20 g·m^-2) <马尾松(Pinus massoniana)林(374.25 g·m^-2) <南酸枣(Choerospondias axillaris)林(537.42 g·m^-2) <青冈林(579.33 g·m^-2), 活细根生物量为杉木林(268.74 g·m^-2) <马尾松林(299.15 g·m^-2) <南酸枣林(457.32 g·m^-2) <青冈林(508.47 g·m^-2), 各森林类型之间的细根总生物量差异显著(p < 0.05), 但活细根生物量差异不显著。土壤垂直剖面上, 除杉木林细根生物量随土层变化不显著外, 其他森林类型的活细根生物量和总细根生物量均随土层变化显著, 表层细根生物量随树种多样性的升高呈减小趋势, 据此推测树种间的生态位分离水平逐渐增大。植物多样性的不同对林分的细根形态及空间分布格局影响不显著, 细根形态可塑性对生物量变化响应不明显。     

Spatial and length distribution,sex composition,and feeding of the notched-fin eelpout <Emphasis Type="Italic">Zoarces elongatus</Emphasis> (Perciformes: Zoarcidae) in the Sea of Okhotsk

Based on the data from six bottom trawl surveys carried out on the shelf of the Sea of Okhotsk in 1997–2007, the features of the distribution, size and sex structure, and food composition of the notched-fin (east) eelpout Zoarces elongatus were analyzed. It was established that this species regularly occurs in trawl catches only in the eastern part of the sea and that the density of its schools decreases with depth. It was recorded that females of the notched-fin eelpout are larger than males. The sex ratio of the fishes varies from year to year. Females prevail at depths less than 25 m and males prevail at depths greater than 25 m.     

A spatial approach to matching marine fish diversity and abundance with habitat features

Current issues in marine resource management have in common a geospatial component and a need to integrate both biotic and abiotic data from various sources. We propose a practical approach to address these issues looking at the American plaice (Hippoglossoides platessoides) and the demersal fish fauna in the Gulf of St. Lawrence (Canada). Central to our approach was the use of a common spatial grid and three different methods to match biotic and abiotic features at a broad regional scale, (1) matching plaice distribution with habitat categories determined a priori on the basis of abiotic features (cluster analysis), (2) habitat categories determined taking into consideration both plaice density and abiotic features (simple regression tree), and (3) habitat categories determined taking into consideration demersal fish species density (70 fish species) and abiotic features (multivariate regression tree, MRT). Hot spots and cold spots of plaice abundance in summer were described and matched with specific habitats. The spatial distribution of habitats was similar whether biotic variables were used in the classification or not. The MRT, however, identified 56 different fish species in the plaice habitat (median species richness by 100 km² cell = 12), pointing to potential interactions with other fish species.     

Age,growth, and reproduction of blackspot snapper Lutjanus fulviflammus (Forsskål 1775) around Yaeyama Islands,southern Japan,between 2010 and 2014

Age, growth, and reproductive characteristics of blackspot snapper Lutjanus fulviflammus around the Yaeyama Islands (24°N, 124°E) in southern Japan were investigated between 2010 and 2014. Samples were caught by angling or purchased monthly at fish markets to cover all size ranges and seasons. Specimens consisted of 280 females (176–347 mm fork length), 177 males (193–325 mm), and 17 juveniles (42–128 mm). Spawning was confirmed from April to August by the presence of postovulatory follicles, which, based on the occurrence of yolked oocytes possibly also occurred in March and September. Maximum fork length and age in the specimens around Yaeyama Islands were 347 mm and 23 years for females and 325 mm and 21 years for males. These results were compared to those reported previously for the species in other regions by standardized criteria. Possible spawning duration of 7 months in the population around Yaeyama Islands is similar to that in New Caledonia (22°S, 5 months) and Okinawa Island (26°N, 6 months), but shorter than that in Tanzania (8°S) and the southern Arabian Gulf (25°N) (~12 months). The maximum body sizes and ages around Yaeyama Islands are also similar to the populations in New Caledonia and Okinawa Island (>300 mm FL, >20 years old), but larger/older than those in Tanzania and the southern Arabian Gulf (<300 mm FL, <20 years old). These differences are thought to reflect water temperature, i.e. spawning duration is shorter in lower temperature regions (annual mean <26°C, New Caledonia, Okinawa Island, Yaeyama Islands) than in higher temperature regions (annual mean >27°C, Tanzania, southern Arabian Gulf). Subsequently, a shorter spawning duration extends the life‐span as well as the maximum body size. Longevity of blackspot snapper is thought to be negatively correlated with the duration of the spawning season.     

Post-release survival and riverine movements of Gulf of Mexico sturgeon (Acipenser oxyrinchus desotoi Acipenseriformes) following induced spawning

Post‐release survival and upstream movement of Gulf of Mexico sturgeon (Acipenser oxyrinchus desotoi) in the Suwannee River, Florida, were examined following induced spawning using carp pituitary extract (CPE). Six mature females (one CPE‐treated and five control) and 12 mature males (five CPE‐treated and seven control) were implanted with ultrasonic tags in March 2001 during their ingress into the Suwannee River. All CPE‐treated sturgeon and 10 of the 12 control fish were relocated using ultrasonic telemetry during 4 months following their release, resulting in 100% survival of treated fish and 83% known survival of control fish. Two control fish (one female and one male) could not be relocated after 2 weeks post‐release. CPE treatment did not result in mortality but did affect upstream movement behavior, with CPE‐treated males moving upstream at a significantly slower rate than control males and females. Similarly, the maximum observed distance that the fish moved upstream differed among control fish (males and females) and treated males, with control fish moving further upstream than CPE‐treated males. The rate of upstream movement for the single CPE‐treated female was similar to the control females and the maximum upstream distance that this female was located was near a putative spawning area. In general, the environmental parameters of temperature, dissolved oxygen, and conductivity differed over the course of the study but did not differ between treatments and sexes. Treating sturgeon with CPE to induce spawning therefore did not cause mortality but did appear to slow the rate of upstream movement and maximum distance moved in male Gulf sturgeon.     

Long-term changes in distribution and demographic composition of thornback ray, Raja clavata, in the northern and central Adriatic Sea

Population structure and distribution of the thornback ray, Raja clavata , L. 1758, in the northern and central Adriatic Sea were described based on data from bottom trawl surveys conducted in the area between 1996 and 2006 within the scope of the 'MEDITS' project. R. clavata was caught at depths between 23 and 270 m; highest abundance and density indices were recorded at a depth stratum 50–100 m. The sex ratio was close to 1 : 1. Length at first sexual maturity for both sexes was calculated. Length–weight relationships were obtained for males, females and the whole sample. Calculated parameters of the length–weight ratio showed a positive allometry for both sexes. The recent state of the population was compared with data from the 1948–49 'Hvar' expedition. The comparison revealed that significant changes have occurred in distribution and abundance of R. clavata in the Adriatic Sea since the time of the 'Hvar' expedition. During the 1948–49 'Hvar' expedition R. clavata was distributed throughout the entire continental shelf; during the 1996–2006 MEDITS expedition the species was found only in restricted areas and with much lower abundances. Significant changes also occurred in the demographic composition of the population. All described changes indicate an over-fishing of the thornback ray in the Adriatic Sea, a result of the high fishing intensity to which the species has been exposed for the past 60 years.     

Distribution and biology of Alepocephalus rostvatus from the Mediterranean Sea

In the Catalan Sea (NW Mediterranean) A. rostratus was found on the bottom below 500 m and reached its maximum abundance and biomass at 1100–1300 m depth, being captured down to 2209 m. Mean fish size increased progressively with depth. Larger fish were predominantly females, and 50% of maturity was reached at 23–6 and 27–7 cm in males and females, respectively. Although a high percentage of the population was mature all year round, a peak was attained in autumn, coinciding with the slowest growth of the species. Size-at-age indicated a slow growth rate. The greatest observed age was 23 years, although most of individuals were 7–12 years old. Overall, A. rostratus can be considered as a typical K-strategist, showing a good adaptation to the oligotropic deepsea environment.     

Comparative growth of wild male and female lions (Panthera led)

Lion growth was studied by fitting sex specific Von Bertalanffy curves and linear regressions to data on body mass, heart girth, shoulder height and vertebral column length. Measurements were recorded for 344 lions ( Panthera leo ) (158 ♂♂ and 186 ♀♀), from Kruger National Park, South Africa. Growth in mass for males and females was linear up to about 36 months of age 0 = 0–98 and 0–99 respectively). The other age-specific measurements were clearly curvilinear. Mean weights for adult lions (excluding stomach contents) were 187–5 kg (♂♂) and 124–2 kg (♀♀) respectively. Lions tended to continue growing up to about seven years in males and nine to 10 years in females after which they usually started to lose condition. Body mass and heart girth measurements of Kruger Park lions were compared with samples from three other populations. These showed that lions from East Africa were smaller than those from more southern populations in Rhodesia, Kalahari and Kruger Park.     

The stock structure and migrations of plaice populations on the west coast of England and Wales

Plaice Pleuronectes platessa populations on the west coast of England and Wales are currently managed as two stocks: in ICES Division VIIa (Irish Sea, Cardigan Bay and St George's Channel), and ICES Divisions VIIf&g (Bristol Channel and Celtic Sea). A total of 13,784 plaice were fitted with Petersen tags and released in these areas during 1979–1980 and 1993–1996. Analysis of the 2788 recaptures received by June 2000 confirmed known spawning and feeding grounds in the region. It showed also that plaice >25 cm L _T tended to undertake extensive spatial movements. At this size, female plaice were likely to be mature or maturing for the first time, whilst males were probably mature. Tag recaptures indicated resident sub-stocks of plaice in the north-east Irish Sea, the south-east Irish Sea, Cardigan Bay and Bristol Channel, a contingent of plaice in all areas that undertook permanent dispersal to other areas, and a contingent which originated in the south-east Irish Sea and migrated to spawn in the Bristol Channel. Plaice originating in the Bristol Channel rarely moved north into ICES Vila. A general hypothesis of plaice population structure in the region is presented and discussed in relation to stock assessment.