Evidence of daily spawning in natural populations of the New Zealand snapper Pagrus auratus (Sparidae)

Synopsis New Zealand snapper, Pagrus auratus, were captured by trawling from NE New Zealand over two successive spawning seasons, and examined for acute temporal changes in gonad condition. Fish with oocytes completing final oocyte maturation predominated during the morning, with a peak in ovulated fish occurring just after midday. Afternoon catches were dominated by fish in which the most advanced oocytes had yet to begin final maturation. This suggests that ovulation is synchronised to occur soon after midday, and the high proportion (up to 100% of the catch) of fish with particular gonad stages captured at any one time indicates that daily spawning involves most of the population. Diurnal changes in oocyte diameter support a daily spawning rhythm, with numbers of large hydrated oocytes peaking in the late morning, followed by the disappearance of these oocyte stages in the afternoon. Snapper captured alive by longlining were returned to the laboratory to examine the relationship between ovulation and probable time of spawning. Unovulated fish generally ovulated close to midday on the day of capture (morning captures), or the following day (afternoon captures). The viability of ovulated eggs (proportion undergoing division after fertilization) decreased markedly after oviduct residence times of over 8 hours. This suggests that natural spawning occurs before the late evening. The results of this study are consistent with anecdotal evidence suggesting that spawning occurs every day during the late afternoon or early evening, and is similar to the reproductive patterns displayed by a number of closely related sparids. Department of Zoology, University of Otago, PO Box 56, Dunedin, New Zealand     

Diel variation in feeding rate and prey composition of herring and mackerel in the southern Gulf of St Lawrence

Diel feeding patterns of herring Clupea harengus and mackerel Scomber scombrus in the southern Gulf of St Lawrence were examined based on samples obtained by midwater trawling between 19 and 26 June 2001. Within 3 h time periods, stomach contents tended to be more similar between fish from the same tow than between fish from different tows. Thus, in contrast to previous diet studies, which have used individual fish stomachs as independent observations, tow was used as the experimental unit in statistical analyses in this study. Diel patterns in stomach fullness were identified using generalized additive models. Two peaks in stomach fullness occurred for herring, one in the morning and the other in the evening. Mackerel showed an increase in feeding intensity throughout the day with a peak in mid‐afternoon. The diel changes in stomach contents suggested rapid gastric evacuation rates for both species, especially for herring. The estimate of the instantaneous evacuation rate for herring was twice that for mackerel. Calanus copepods (mainly C. hyperboreus ), fishes (mainly capelin Mallotus villosus ) and euphausiids were the main prey found in the stomachs of both species. Calanus copepods dominated the diet of herring regardless of time period. They also dominated the diet of mackerel during the late afternoon, evening and night while fishes and euphausiids were dominant during the morning and early afternoon. These diel patterns emphasize the need for sampling throughout the day and night in order to estimate ration and diet composition for bioenergetic and ecosystem models.     

The diurnal patterns of behaviour of the wild Barbary macaque Macaca sylvanus

The daily routine of a population of wild Barbary macaques is described. The day journey is mainly on the ground with the animals taking to the trees only for sleeping, resting, avoiding predators and, during some seasons, for feeding. Two methods (based on individual activity records and on social interactions) were used to measure the diurnal distribution of behaviour. In the summer, feeding was bimodally distributed with peaks morning and afternoon. The initiation of social interactions peaked at the same time, owing to the frequent use of agonistic behaviour to maintain individual distance while feeding. The reduction in feeding at midday was accompanied by an increase in allogrooming and resting and in the proportion of animals in the trees. Peaks of friendly approaches and in the initiation of interactions involving unweaned monkeys (excluding play, maternal behaviour and agonistic behaviour) occurred on either side of the midday rest period and in the evening. In the winter, there was no midday rest period; grooming decreased throughout the day while feeding increased. Sexual behaviour was rare during the summer.     

Sea trout in North Argyll sea lochs: II. diet

The diet of sea trout in some of the sea lochs of the west coast of Scotland was investigated. The contents of 986 sea trout stomachs from the Loch Etive area (1970–1973), and 291 stomachs from the Loch Eil area (1964–1973), were examined and the composition of the diet, seasonal changes and the effect of trout size were analysed using frequency of occurrence, dry weight and number of organisms methods. Benthic feeding (crustacea and annelids) was more important in winter while midwater and surface organisms (young fish and insects) were preferred in summer. Young fish (mainly clupeids and sand eels) featured more in the diet of larger trout (≤21 cm) than in the smaller size range (≥21 cm). Surveys of 24-h were completed in June and September, 1972, and indicated that availability of food was the main factor influencing the presence or absence of trout. Bottom feeding was greatest during the day while the amount of midwater and surface feeding tended to increase between sunset and sunrise.     

笼养黄腹角雉繁殖期取食活动性的研究

笼养条件下黄腹角雉繁殖期的日取食活动呈现早、中、晚三个高峰;雄鸟在交配前后的日取食活动无显著差异,雌鸟的日取食活动在不同繁殖阶段则出现规律性的变化。逐步回归分析的结果表明:影响雄鸟取食的主要因素是总活动时间、炫耀次数和走动时间,影响雌鸟取食的因素主要是理羽时间、飞行次数和跳跃次数。     

Viable bacterial aerosol particle size distributions in the midsummer atmosphere at an isolated location in the high desert chaparral

The viable bacterial particle size distribution in the atmosphere at the Hanford Nuclear Reservation, Richland, WA during two, 1-week periods in June 1992, was observed at three intervals during the day (morning, midday and evening) and at three heights (2, 4, and 8 m) above ground level. The distributions were significantly different (P=0.01) between the two, 1-week sampling periods and between morning, midday, and evening observations, but not between the three heights. Approximately 30 to 50% fell into the largest particle size category; 7.0µm aerodynamic diameter. All particle size categories were at their minimum bacterial concentration at around noon, with the lowest concentrations in the smaller size categories (<2.1µm aerodynamic diameter). This suggests, that at this high desert location, solar radiation (SR) damage to airborne bacteria is particle size discriminatory. There is a relatively greater effect on the smaller size categories at midday and a relatively lesser effect in the morning and evening.     

The Diel Rhythms of Biosonar Behavior in the Yangtze Finless Porpoise (Neophocaena asiaeorientalis asiaeorientalis) in the Port of the Yangtze River: The Correlation between Prey Availability and Boat Traffic

Information on the habitat use of the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is critical for its conservation. The diel biosonar behavior of the porpoise in the port areas of the Yangtze River was examined along with simultaneous observations of fish density and boat traffic. Biosonar pulses from the porpoises were detected for 1233 min (5.77%) over a 21,380 min duration of effective observations. In total, 190 (5.63%) buzzes (an indication of prey capture attempts) were recorded among the 3372 identified click trains. Of the 168 echolocation encounters (bouts of click trains less than eight min apart), 150 (89.3%) involved single animals, indicating that solitary porpoises were frequently present and feeding in the port areas. Significant diel patterns were evident involving the biosonar behavior of the porpoises (including click trains and buzzes), fish density and boat traffic. The frequencies of the click trains and buzzes were significantly lower during the day than in the evening and at night, which suggests that porpoises in this region are primarily engaged in crepuscular and nocturnal foraging. The lack of a significant diel pattern in the echolocation encounters indicates the importance of the port in porpoise conservation. A forced feeding schedule may be associated with the lack of a significant correlation between porpoise acoustics and boat traffic. Overall, prey availability appears to be the primary factor that attracts porpoises. Additionally, porpoises tend to migrate or remain downstream in the morning and migrate or remain upstream in the evening, most likely to follow their prey. The findings of this study can be used to improve the conservation of the Yangtze finless porpoise.     

Diel changes in invertebrate drift and the food of trout Salmo trutta L.

Diel changes in the stomach contents of 0+, 1 + and 2+ or older trout were compared with diel changes in invertebrate drift. Peaks in mean numbers and biomass of invertebrates per fish stomach occurred in the midday (10.00 to 14.00 h) and evening (18.00 to 22.00 h) samples. The major peak was usually in the evening sample, but the major peak in biomass was in the midday sample for 2+ fish. There was a good correlation between diel changes of benthic invertebrates in the diet and drift, with the major peak in the evening. A similar relationship did not always exist for emerging and terrestrial invertebrates. Known non-drifting benthic invertebrates (e.g. large caddis larvae) were excluded from the comparisons, and were only taken by 2+ or older trout in which they contributed a large biomass to the day food.     

Food consumption of yellowfin tuna,Thunnus albacares, in Sri Lankan waters

Synopsis A total of 4181 stomachs of yellowfin tuna,Thunnus albacares (22–164 cm FL), mainly caught by gillnets in the period from July 1984 to June 1986 were analyzed. Food consumption of yellowfin tuna in nature was determined using the values of the average stomach content, incorporating laboratory measurements of gastric evacuation rates in a feeding model. The diet of yellowfin tuna around Sri Lanka comprised a variety of macro zooplanktonic and nektonic organisms. Juveniles < 39 cm FL, are planktivores. Tuna > 40 cm FL gradually increase their consumption of fishes with increasing size. Among fish speciesAuxis sp. are the most important. The daily food consumption of juvenile yellowfin tuna (22–59 cm FL) range from 1.8 g to 136.2 g, increasing to about 284.7 g to 551.9 g for the medium size tuna (60–99 cm FL). The adult tuna (100–>130 em FL) consume around 513 g to 538.8 g of prey per day. Daily ration estimates increase from 2.1% to 5.5% of body weight with increasing size up to 70 cm FL, beyond which it decreases. The predatory pressure of yellowfin tuna on commercially important fishes and other species is discussed.     

Temporal Variation in Cleanerfish and Client Behaviour: Does It Reflect Ectoparasite Availability?

We tested the importance of ectoparasites as the proximate cause of cleaning interactions by comparing the activity of Caribbean cleaning gobies (Elacatinus evelynae) and of their clients during three daily periods (early morning, midday, and late afternoon) in which ectoparasite availability varied naturally. Emergence from the benthos of gnathiid isopod larvae, the main target of cleaning goby predation, was higher at night, when cleaners were inactive, than during the day. As a result, overall ectoparasite loads on client fish tended to be higher in the morning. Inspection bouts by cleaning gobies were longest in the morning, but also at midday when ectoparasite availability on clients was lower. Client fish were observed at cleaning stations most often in the afternoon, when they harboured few ectoparasites, but they were more likely to adopt incitation poses, which increase the likelihood of being cleaned, in the morning than later in the day. Most cleaner and client behaviours therefore did not change predictably in response to natural diurnal variation in ectoparasite availability. Our study suggests that the ultimate and proximate causes of cleaning behaviour need not necessarily coincide.     

Overlapping territory of the benthophagous cichlid fish, Lobochilotes labiatus, in Lake Tanganyika

Synopsis Feeding territories do not usually overlap in the same fish species. We studied overlapping territories and feeding behaviours of a benthophagous cichlid fish Lobochilotes labiatus Boulenger in a coastal area of Lake Tanganyika. Forty-four individuals of both sexes, 6–31 cm in total length, maintained territories in a 21 m × 25 m area. These could be regarded as feeding territories. The territories of similar-sized owners (usually different by less than 5 cm) did not overlap each other, but those of different-sized owners overlapped widely. Aggressive interactions were rarely observed between fish distinctly different in body size. Both large and small fish took benthic animals of the same kinds and of similar size. In contrast, the size of foraging sites (crevices) was different between them: the large fish foraged at large crevices and small fish at small crevices. This partitioning of foraging sites may enable the overlap of territories in this benthivore.     

Influence of diurnal rhythms of feeding during intestine total amylolytic activity and activity of alkaline phosphatase in juvenile fish

The total amylolytic activity and activity of alkaline phosphatase in the intestine mucosa of larvae and fries of roach, blue bream, and perch change both during the process of individual development and during the day. Maximal intensities of juvenile feeding was observed primarily in the morning and evening hours. The pattern of diurnal alkaline phosphatase activity correlates to a greater extent to intensity of juvenile feeding, in comparison to the pattern of total amylolytic activity. In planktivorous blue bream, such regularity is more pronounced than in benthivorous roach. The total amylolytic activity in fries of roach, blue bream and perch correlates to fish type of feeding.     

Diurnal regulation of ribulose-1,5-bisphosphate carboxylase/oxygenase activity and its content in Norway spruce needles

Diurnal changes of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity and its content were measured to find the mechanism of RuBPCO activity regulation in Norway spruce needles. Both initial and total RuBPCO activities as well as the activation state had a typical pattern with two peaks in the morning and afternoon, respectively, and a midday depression. On the 19 October, RuBPCO content decreased during the day from 3.1 to 1.4 g m⁻², while on the 20 October it was approximately constant both in the morning and in the afternoon (2.7 g m⁻²). Neither initial nor total activity of RuBPCO copied irradiances. Relatively low morning and evening values of total activities indicate that nocturnal inhibitor CA1P is important in Norway spruce. However, the midday depression of total activity indicates that besides CA1P there function some other inhibitors of RuBPCO. In addition, the diminution of RuBPCO content during the day may indicate repression of its gene expression.     

Intraspecific agonistic interactions in freely swimming mormyrid fish, Marcusenius macrolepidotus (South African form)

South African bulldogs (Marcusenius macrolepidotus, Mormyridae) generate brief (less than 1 ms) electric organ discharges (EODs), separated by much longer and highly variable inter-discharge intervals (IDIs). The diurnal and nocturnal overt behaviour and electrical activity were studied under various conditions: in isolated fish, in pairs of fish, and in a group of four fish that were kept in a "natural" large aquarium. EODs from up to four individuals were recorded simultaneously and identified. While resting during the day, isolated fish showed a broad inter-individual variability of IDI patterns, with distribution histogram modes ranging from 85.7 ms to 325.8 ms. When foraging during the day, IDI modes were shorter and less variable (36.3–48.3 ms). Behaviour patterns displayed during nocturnal agonistic encounters were retreating, parallel swimming, anti-parallel display, attack, and fleeing/chasing. High-discharge-rate (HD) displays were observed at several stages of these encounters, for example, during anti-parallel display (a period of low overt motor activity), or following attacks. IDI durations as short as 11 ms occurred during HD displays, which followed low-rate inter-HD activity almost without transition. IDI distribution histogram modes when fish showed anti-parallel display were 15.4 ms and 24.8 ms, and 30.0 ms during nocturnal non-agonistic interactions. No overt fighting was observed once a dominance relationship was established. In a large aquarium, an approaching dominant male evoked a simultaneous discharge arrest in a group of three subdominant males. Electronic Publication     

Intertidal territoriality and time-budget of the surgeonfish, Acanthurus lineatus, in American Samoa

Synopsis The herbivorous surgeonfish Acanthurus lineatus aggressively maintained feeding territories in the surf zone of the outer reef flat in American Samoa. Intertidal territories were re-established each morning, as well as after displacement by low tides or rough surf. Day-to-day site fidelity of recognizable individuals was high: 99.9% return rate per day for adults (15–20 cm), 99.6% for juveniles (8–13 cm), and 97.2% for recruits (2.5–5 cm). Fish fed on turf algae primarily in the afternoon (80% of available time), and spent 10% of their time on active territorial defense and 2–13% of their time on forays from their territory. On average, a fish defended its territory 1900 times daily and took 17 000 bites (= 7400 bites m^–2 d^–1), but rough surf reduced feeding by 60% and defense by 75%. High territorial defense requirements significantly reduced feeding rates. Although the distribution and behavior of this species in Samoa was in large part similar to that reported for it elsewhere (Australia, Indian Ocean), there were notable differences: in Samoa A. lineatus densities within colonies were greater (0.4 fish m^–2), territory size was smaller (2.3 m²), and defense rate against intruders was greater (2.5 attacks min^–1). These differences in Samoa may be related to their smaller body size, greater abundance or increased food supply caused by hurricane damage to reefs which has enhanced the algal turfs that A. lineatus feeds upon.     

Aspects of the Natural History of the Arboreal Harvestman <Emphasis Type="Italic">Cynorta marginalis</Emphasis> (Opiliones: Cosmetidae) Inhabiting a Costa Rican Forest

Relatively little is known about the natural history of the cosmetid harvestmen that inhabit the forests of Central America. The primary objective of this study was to investigate habitat use among adult Cynorta marginalis. In the field, we established 15 transects (40 m in length) and sampled them repeatedly in the morning (0830–1100 h) and evening (1800–2300 h). During 45 morning and 35 evening surveys, we captured and marked 146 males and 112 females. Only three individuals (all females) were recaptured over the course of the study, indicating that the population size at this field site was relatively large. Heavy rains significantly reduced the surface activity of adults (1.1 individuals per transect during heavy rain vs. 3.7 individuals per transect during light or no rain). Harvestmen most commonly used leaves (65% of captures) or tree trunks (31%) as perches, and rarely occupied branches or the leaf litter. Only 18 adults were observed with leg injuries, with two individuals having damage to multiple legs. Perch height was significantly lower during the evening (110.9 cm at night vs. 155.1 cm during the day). Adults were most commonly found alone (85%), however, we observed several harvestmen in male-female pairs (8%), same sex pairs (4%) and heterosexual groups (3%). Although we did not observe reproductive or aggressive behaviors in the field, we observed intraspecific interactions under laboratory conditions and found that some individuals (15%) engaged in courtship suggesting that the sharing of perches by male-female pairs may be related to reproductive activity.     

Status-dependent foraging behaviour in coral reef wrasses

Field observations using underwater video were used to reveal differences in the duration and frequency that fish engaged in daily behaviours such as chasing, searching, feeding, and travelling, according to their social patterns [passive or aggressive terminal phases (TPs), pair-spawning, or promiscuous groups] and intraspecific status (terminal or initial colour phases). Marked differences were apparent according to status, but this was not consistent among the three species; TP Cheilinus fasciatus tended to swim in longer bouts with less frequent searching or feeding than initial phase (IP) conspecifics; TP Cirrhilabrus punctatus exhibited less frequent feeding and travelling than IP conspecifics, while the most aggressive species Stethojulis bandanensis displayed no significant intraspecific differences. We highlight the importance of social context and individual status when examining fish foraging activities and the utility of underwater video for recording the duration and frequency that fish engage in essential daily activities.     

Temperature constraints on foraging behaviour of male Alpine ibex (Capra ibex) in summer

In arctic and alpine environments, warm summer temperatures may force a reduction in foraging time of large herbivores, whose tolerance for heat is lower than for species adapted to warmer weather. We constructed time budgets for marked ibex (Capra ibex) males over two summers to test whether warm temperatures constrained foraging behaviour and forced altitudinal migrations. As daily temperature and solar radiation increased, feeding activity was reduced at midday and evening, but increased in the early morning, probably to anticipate for an expected reduction in foraging later in the day. With increasing temperature and solar radiation, ibex moved to higher elevations where they spent very little time feeding. Changes in forage quality and availability could not explain altitudinal migration. Temperatures above 15–20°C apparently result in heat discomfort in male Alpine ibex. As temperature and solar radiation increased, older and larger ibex spent less time feeding during daylight and showed a steeper decrease in feeding time than younger and smaller ibex. Larger males may be more sensitive to temperature and solar radiation, or may have more flexibility in allocating time to different activities, given their lower relative energetic requirements. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The combined effect of feeding time and ration on growth performance and nitrogen metabolism of greenback flounder

Greenback flounder Rhombosolea tapirina ( c. 2 g) fed to satiation had significantly ( P <0·01) higher feed consumption in the evening than in the morning whereas there was no difference between feeding times for flounder fed restricted rations (1 or 2% body weight per day) because they consumed all of the ration. Differences in growth performance were due to feeding time and ration. Carcass moisture, lipid and energy content were significantly ( P <0·001) different between rations; length gain was significantly affected by feeding time ( P <0·05) and ration ( P <0·001); weight gain showed a significant ( P <0·001) interaction between feeding time and ration. The relationship between feed consumption and specific growth rate showed that the exponential gradient was significantly higher ( P <0·01) for the evening fed fish and indicated feed efficiency for evening fed fish increased as feed consumption increased. Urea excretion increased from 12–20 to 58–63% of total nitrogen excretion at the 1 and 3% rations, respectively. Ammonia and urea excretion were significantly affected by ration ( P <0·001) and feeding time ( P <0·05). Fish fed the 2% ration in the evening had higher growth efficiency and significantly ( P <0·01) lower rates of urea excretion than fish fed 2 or 3% ration in the morning. It is suggested that the higher energetic costs associated with differences in ammonia and urea excretion contributed to differences in growth efficiency.     

Diurnal rhythms of body temperature, heart rate, and behaviour in the stanchioned adult Shiba goats

Using a data logger system, body temperature (dorsal subcutaneous temperature), heart rate, ingestive or ruminating behaviour and posture in adult Shiba goats tied to a stanchion were recorded automatically during 24 hours, to obtain basic information on the biological rhythms. A 600 g of usual ration mixed with hay cube, hay, beet pulp and wheat bran was fed twice a day (morning; 9:00-9:30, evening; 16:00-16:30). Animals kept under an artificial photoperiod (12L-12D, light period; 5:30-17:30) and about 10 degrees C room temperature. 1) Diurnal patterns of the above-mentioned items were recorded, mutual relationships relationships between these items were revealed. 2) The heart rate was higher after morning feeding, or during a light period and decreased gradually from midnight to early morning. Twice feeding greatly increased the heart rate. 3) The body temperature was lower in the early morning and increased gradually after morning feeding and showed the highest level during 1 to 1.5 hours after evening feeding. After that it decreased gradually till the early morning. 4) The numbers of jaw movement (bites/min) were a 70-90 bites in the ingestive behaviour and a 80-90 bites in the ruminating behaviour at dark period. 5) The total heart rate was a 110000 to 120000 beats/day, the total biting time was a 9.5 hours/day, and the mean standing time was a 9.3 to 11.7 hours/day. The standing time during light period (12 hours) was a 7.3 to 9.9 hours and that during dark period (12 hours) was a 1.8 to 2 hours.