Diel Behavior Research Articles

Reproductive biology of Vinciguerria nimbaria in the equatorial waters of the eastern Atlantic Ocean

Adult Vinciguerria nimbaria in an area of the Atlantic Ocean (0–5°N; 10–20°W), collected from November 1994 to February 1998, exhibited two different patterns in diel behaviour: ‘typical’ behaviour which consisted of large diel vertical migration and ‘atypical’, characterized by concentrations of schools that remained in the surface layers during the daytime. The total life span of V. nimbaria was estimated at 6–7 months. Females were mature when they reached 30·6 mm standard length (LS), which corresponded to an age of 85 days. Once the females were mature, spawning was continuous in the population as a whole, and V. nimbaria spawned continuously throughout the year. Spawning took place during two restricted times of the day: typical females spawned at dusk and atypical females spawned at dawn. Using the post‐ovulatory follicles method, spawning frequency was estimated at 2 days. Batch fecundity was estimated at 1236 oocytes or 1230 oocytes g−1 of total body mass, and egg size was 650 µm whatever the period of the year. The lifetime fecundity of V. nimbaria was estimated at 9000 eggs (109 000 eggs if mortality rate was not taken into account), and the maximum stock egg production of a theoretical cohort occurred at 37 mm LS. Young adults thus contributed the most to the reproductive output for the survival of the population.

Ontogenetic Behavior, Migration, and Social Behavior of Pallid Sturgeon, Scaphirhynchus albus, and Shovelnose Sturgeon, S. platorynchus, with Notes on the Adaptive Significance of Body Color

We conducted laboratory studies on the ontogenetic behavior of free embryos (first life interval after hatching) and larvae (first feeding interval) of pallid and shovelnose sturgeon. Migration styles of both species were similar for timing of migration (initiation by embryos on day 0 after hatching and cessation by larvae on days 12–13 at 236–243 cumulative temperature degree units), migration distance (about 13 km), life interval when most distance was moved (embryo), and diel behavior of embryos (diurnal). However, the species differed for two behaviors: movement characteristics of embryos (peak movement rate of pallid sturgeon was only one-half the peak rate of shovelnose sturgeon, but pallid sturgeon continued the lower rate for twice as long) and diel behavior of larvae (pallid sturgeon were diurnal and shovelnose sturgeon were nocturnal). Thus, the species used different methods to move the same distance. Migrating as poorly developed embryos suggests a migration style to avoid predation at the spawning site, but moving from spawning habitat to rearing habitat before first feeding could also be important. Migrants of both species preferred bright habitat (high illumination intensity and white substrate), a behavioral preference that may characterize the migrants of many species of sturgeon. Both species were remarkably similar for swimming height above the bottom by age, and day 7 and older migrants may swim far above the bottom and move far downstream. A migration of 12 or 13 days will probably not distribute larvae throughout the population's range, so an older life interval likely initiates a second longer downstream migration (2-step migration). By day 2, individuals of both species were a black-tail phenotype (light grey body with a black-tail that moved conspicuously during swimming). Aggregation behavior suggests that black-tail is a visual signal used for group cohesion.

A study of photochemical and physical processes affecting carbonyl compounds in the Arctic atmospheric boundary layer

Experiments were conducted during the ALERT 2000 field campaign aimed at understanding the role of air–snow interactions in carbonyl compound chemistry and the associated ozone depletion in the atmospheric boundary layer. Under sunlit conditions, we find that formaldehyde, acetaldehyde and acetone exhibit a significant diel cycle with average ambient air concentrations of 166, 53 and 385 ppt, respectively. A box model of Arctic surface layer chemistry was used to understand the diel behavior of carbonyl compound concentrations at Alert, Nunavut, Canada, with a focus on the chemical and physical processes that affect carbonyl compounds. Results of the study showed that the measured carbonyl compound concentrations can only be simulated when a radiation-dependent snowpack source term (possibly photochemistry) and a temperature-dependent sink (physical uptake on snow grains) of carbonyl compounds were added to the model. We are able to simulate the concentration and amplitude of the observed diel cycle, but not the phase of the cycle. These results help confirm the importance of snowpack chemistry and physical processes with respect to carbonyl compound concentrations in the Arctic surface boundary layer, and reveal weakness in the details of our understanding.

Three-dimensional visualization of a widow rockfish (Sebastes entomelas) shoal over interpolated bathymetry

Acoustic data from repeated acoustic surveys of a shoal of widow rockfish ( Sebastes entomelas ) were portrayed as three-dimensional images over an interpolated bathymetric surface. Through development of a number of sub-programs which defined the relationships between different elements of the data, the large data sets could be quickly processed and visualized to gain an understanding of fish distribution, density, and behaviour. The images facilitated discussion of the survey results with commercial fishers and added credibility to the biomass estimates. The images allowed fishers to verify that the density and size of the shoal during the surveys was typical of what they had seen on their sounders and had wanted assessed. The images also confirmed that the shoal's spatial extent had been fully surveyed. Furthermore, the images were effective for examining the diel behaviour of the shoal and communicating to the scientific community the habitat affinity of this species to high relief bottom topography.

Zooplankton distribution and behaviour in the Southern Ocean from surveys with a towed Optical Plankton Counter

Spatial distributions of zooplankton with lengths between about 500 μm and 8 mm are described from surveys in the vicinity of the Antarctic Polar Front in austral summer 1995/6 using an Optical Plankton Counter mounted on a towed profiling SeaSoar. The distributions, split into several logarithmically spaced size classes, are compared and related to the physical environment south of the Polar Front in the Antarctic Zone and within the Polar Frontal Zone. They also are compared with phytoplankton distributions determined from surface chlorophyll data. Both phytoplankton and zooplankton carbon densities are low in the Antarctic Zone (2–3 g C m−2), but rise to larger values in the Polar Frontal Zone (5–7 g C m−2 for zooplankton and a maximum of 6 g C m−2 at fronts for phytoplankton). Calibration of OPC derived zooplankton biovolume to carbon was achieved by comparison with dry weights from multinet samples deployed in conjunction with CTD casts. The net data showed that over 98% of zooplankton counts were copepods. Diel behaviour also was examined. Only larger copepods (over 2 mm long) displayed significant diel migration, and then only 10–20% of the standing stock; the majority remained deeper than about 100 m and their distribution patterns suggest that they may be retained aside from the main frontal jets by ageostrophic circulations associated with the front. Copepods shorter than 2 mm rose from depth over the month-long survey to become concentrated in the surface layer (the top 70–100 m). The largest copepods that could be resolved, with lengths of about 4–8 mm (possibly Rhincalanus gigas), displayed unexpected behaviour in tending to migrate to the top 0–10 m by day, descending to 40–50 m each night.

Diurnal vertical migration of the Atka mackerel Pleurogrammus monopterygius as shown by archival tags

Atka mackerel Pleurogrammus monopterygius were captured and tagged with depth and temperature recording devices (archival tags) on 23 July 2000 in Seguam Pass, Aleutian Islands, Alaska. Nine of the 117 tagged fish were recovered in Seguam Pass during September 2000. Fish were tagged externally just below the dorsal fin. Atka mackerel displayed strong diel behavior, with vertical movements away from the bottom occurring almost exclusively during daylight hours and little to no movement at night. Vertical movements occurred when light levels at 150 m were greater than 7.31 × 10 -5 µmol photons m -2 s -1 , or approximately between 08:00 and 23:00 h Alaska Daylight Time (ADT; GMT - 8) during August. Daytime vertical movements were correlated with light inten- sity, time of day and current velocity. The occurrence of vertical movements tended to increase with increasing light during the morning and early afternoon, but then decrease with increasing hour of the day after 13:00 h ADT. The magnitude of surface-directed vertical excursions was reduced dur- ing spring tide periods, when current velocities are highest. By comparison, the magnitude of slope- directed excursions was greater during spring tide periods and reduced during neap tide periods. Eight fish were at liberty for 42 to 44 d and 1 for 65 d. Two of the tagged males displayed nest guard- ing behavior for the majority of their time at liberty. Depths for these 2 males (115 to 117 m) were much deeper than previously observed for Atka mackerel spawning grounds. Given that Atka mack- erel are more likely to be on the bottom during the night and less likely during the day, the variance of abundance estimates from bottom trawl surveys may be reduced by accounting for these diel differences.

A study of formaldehyde chemistry above a forest canopy

Gas‐phase formaldehyde (HCHO) was measured at a mixed deciduous/coniferous forest site as a part of the PROPHET 1998 summer field intensive. For the measurement period of July 11 through August 20, 1998, formaldehyde mixing ratios ranged from 0.5 to 12 ppb at a height ∼10 m above the forest canopy, with the highest concentrations observed in southeasterly air masses. Concentrations varied on average from a mid‐afternoon maximum influenced by photochemical production of 4.0 ppb, to a late night minimum of 2.2 ppb, probably resulting from dry depositional loss. An analysis of local HCHO sources revealed that isoprene was the most important of the measured formaldehyde precursors, contributing, on average, 82% of the calculated midday HCHO production rate. We calculate that the nighttime HCHO dry deposition velocity is 2.6 times that of ozone, or approximately 0.65 cm/s. In the daytime, photolysis, dry deposition, and reaction with hydroxyl radical (OH) are roughly equally important as loss processes. Explicit calculations of HCHO chemical behavior highlighted the probable importance of transport and surface deposition to understanding the diel behavior of formaldehyde.

On Habitat Specificity, Life Cycles, and Guild Structure in Tiger Beetles of Central Amazonia (Brazil) (Coleoptera: Cicindelidae)

Studies on tiger beetle guilds are promising to shed light on general mechanisms that maintain species diversity in the tropics. Therefore this family was studied across a range of habitat types of Central Amazonia in the vicinity of Manaus (open areas and forests on terra firme as well as in white-, mixed-, and blackwater floodplains). In addition to analysis of regional species distribution (extents of habitat specificity), local spatio-temporal guild structures were investigated in order to infer mechanisms mediating coexistence within guilds. Here the results of extensive field observations on habitats, life cycles, and behaviour are summarised for both larvae and adult beetles of most of the 25 species known to occur in the region. Field work was carried out from 1991-99, of which 2-6 years were spent in each habitat. Additionally, life cycles of species were studied by rearing them in the laboratory. At the regional scale, species richness is related with regional habitat diversity, likely because habitat specificity is strong in most species. At the local scale, spatio-temporal guild structure is determined by different life cycles, diel activity patterns, microhabitat preferences and behaviour. Guild structures vary according to habitat types. Guilds from open floodplain areas show strong niche separation whereas guilds from terra firme forest floors exhibit wide niche overlap, with floodplain forests and open terra firme areas lying in between. Thus, tiger beetle guilds of Central Amazonia seem to be variously structured, which indicates different mechanisms mediating coexistence. Possible relations of guild structure with habitat properties are discussed.

Day–night and depth effects on catch rates during trawl surveys in the North Sea

Data from the Scottish participation in the International Young Fish Survey for the period 1976–1993 were analysed to examine the effect of light level and depth on catch rates. The species selected for this study were common dab, herring, haddock and whiting. Differences between day and night were observed for the juvenile common dab and herring and for the adult common dab and haddock. Differences between shallow and deep water were observed for the juveniles of all the species and for the adults of common dab, haddock and whiting. The mean lengths and the composition of the common dab and whiting catches were affected by both light and depth, indicating behaviour differences between the juveniles and adults of these species. Whilst light seems to have no effect on the mean length and the catch composition of herring, differences were observed between shallow and deep waters. In the case of haddock, neither the light level nor the depth had any noticeable effect on the mean length and catch composition of the catches. We conclude that the diel behaviour and the geographic distribution are important factors in determining the quantity and composition of trawl catches, but their effects are species dependent. When trawl surveys are not exact replicates in terms of fishing times and areas, the estimation of catch indices should allow for the possible bias introduced by these factors. There is a need for models of the capture process that take account of such effects.

Summer diel activity and movement of adult brown trout in high‐elevation streams in Wyoming, U.S.A.

The variation in diel activity patterns was determined by implanting transmitters in adult brown trout of various sizes in two montane streams in two summers in the central Rocky Mountains, U.S.A. More brown trout tended to be active, and to move greater distances, each hour during twilight and night than during the day. Mean hourly light intensity was significantly negatively correlated with the proportion of fish active and with the distance moved. Maximum water temperature was not correlated with any measure of diel activity. Brown trout displayed fidelity to diurnal positions within a given diel cycle. Overall, fish were active an average of 11 h, had an average home range of 41 m, and moved an average of 121 m over the diel cycle. Fish length and distance moved were significantly positively correlated. Water temperature, predator avoidance, and foraging tactics may influence these patterns of diel behaviour in adult brown trout in U.S. streams.

Habitat utilization and diel behavior of juvenile bull trout (Salvelinus confluentus) at the onset of winter

Abstract— Underwater observations were used to describe habitat use and diel behavior of juvenile bull trout (Salvelinus confluentus) at the onset of winter (0.8°C) in a second‐order central Idaho stream. All fish observed during daytime counts were concealed beneath “home stones” (mean dimensions 32.3 by 21.9 cm) in primarily pool and run habitats. Focal point depths and velocities averaged 57.2 cm and 4.7 cm/s (home stone removed). Fish maintained stations over substrate with low percentages of fine (< 2 mm, mean= 5.2%) sediment. Concealed bull trout were not evenly distributed across the stream channel. Significantly more home stones were distributed near the midline of the channel, compared to the channel margins. Fish size was positively correlated with home stone size. At night, bull trout exhibited a diel behavioral shift, some fish moved out of daytime concealment cover into the water column. At night, bull trout were observed feeding and resting, primarily in pool and run habitats. During both day and night, bull trout used riffles significantly less frequently than those habitats were available.

Preliminary results on nitric oxide emission from a southern African savanna ecosystem

During October to December 1994, we measured diel and seasonal variability in nitric oxide (NO) exchange by a southern African savanna ecosystem (Grasslands Research Station, Marondera, Zimbabwe). A set of automated dynamic chambers was installed in three sub-sites: Miombo forest, natural grassland, and cropped soils (maize, sorghum, groundnut). The latter received a single application of commercialy available in-organic or cowdung fertilizer. The dynamic chamber system is described in detail, including correction of the resulting data for wall losses and gas-phase reactions of the NO-NO2-O3 triad. During the dry season, net vertical NO fluxes were close to the detection limit (0.44 ngN m-2s-1) regardless of vegetation type. During the transition from dry to wet season strong "pulsing" effects of the NO flux were observed: NO emissions increased by a factor of up to 60 within hours. During the wet season, NO emissions varied between the different sub-sites of the ecosystem; corresponding means are in ranking order of fertilized agricultural plots (27.2 ngN m-2 s-1), unfertilized agricultural plots (8.5 ngN m-2 s-1 ), grassland (4.4 ngN m-2 s-1 ), and Miombo forest (1.5 ngN m-2 s-1). Soil moisture was found to be the dominant factor controlling the NO fluxes. Whenever it was not limiting, the diel behaviour of NO emission followed the daily variation of soil temperature measured 1 cm below the surface.

Emission of monoterpenes and isoprene from a Mediterranean oak species Quercus ilex L. measured within the BEMA (Biogenic Emissions in the Mediterranean Area) project

We report on some results of our studies of monoterpene and isoprene emissions and the physiological activities of an oak species ( Quercus ilex L.) under the Mediterranean climatic conditions found at Castel Porziano (Rome) in June 1993. The oak species Quercus ilex L. was found to emit mainly monoterpenes in high amounts. Isoprene emissions were negligible. Diel cycles of monoterpene emissions showed correlation with light and the diel behaviour of photosynthetic CO 2 assimilation, transpiration and stomatal conductance. Temperature dependence seemed to be of minor importance.

Acoustic evidence for unusual diel behaviour of a mesopelagic fish (Vinciguerria nimbaria) exploited by tuna

For 15 years, there has been a seasonal tuna fishery in the open equatorial Atlantic Ocean. There are no good reasons for explaining this concentration of fish, except the possible abundance of micronekton. However, micronekton are only found during the night in the upper layers, whereas tuna feed during the day, according to current assumptions. An acoustic cruise carried out in November 1992 clearly showed the presence in this area of a large schooling biomass of a small mesopelagic fish, Vinciguerria nimbaria (Photichtyidae). Instead of diving to a great depth during the day as usual, they remained in the upper layers and tuna (Katsuwonus pelamis and Thunnus albacares) were found to feed on them. The atypical behaviour of Vinciguerria involved two processes: reverse phototaxis and a break in the diel vertical migrations. A review of the literature shows that this fish: (1) is a common item in tuna stomach contents; and (2) is never caught in the upper layers during the day. This apparent discrepancy has been resolved by our results: schooling behaviour during the day prevents Vinciguerria from being sampled adequately by the usual systematic net tows. The need to use acoustics for successful sampling is obvious. It is likely that this behaviour occurs in other areas and could explain the local concentration of tuna.

Evidence of in situ diel vertical migration of a red-tide microplankton species in R�a de Vigo (NW Spain)

The migration capacity of red-tide species in the natural environment was studied at a station in the Ria de Vigo (Rias Bajas, NW Spain) over a 24 h period in September 1991. The Ria de Vigo, where red tides are frequent, normally shows a positive estuarine circulation and is subjected to seasonal upwelling and downwelling phenomena. A marked diel pattern was observed for five species that are capable of causing red tides (Ceratium furca, Scrippsiella trochoidea, Dinophysis acuminata, Mesodinium rubrum, and Eutreptiella sp.). Such diel behaviour could be clearly advantageous in a stratified environment where light and nutrients are often in two separate layers. Active movement enables species such as dinoflagellates and some ciliates to exploit high levels of irradiance at the surface during the day and to take up nutrients in deeper layers at night. Patchy distribution of phytoplankton, shear-induced horizontal dispersion and density variations were considered, but none of them accounted for the vertical changes observed. Vertical migration is thought to be one of the mechanisms that could promote blooms in nutrient-depleted surface layers.

Day-night migrations by deep-sea decapod crustaceans in experimental samplings in the Western Mediterranean sea

Analysis of abundance and size frequency data on decapod crustacean species in two different habitats (inside and outside a submarine canyon) in the Western Mediterranean during two near-continuous 24-h sampling periods using commercial bottom trawls provided an indication of migratory ability and activity of the numerically dominant species. Certain nektobenthic species (e.g. Aristeus antennatus) carried out migrations up the slope at night. Mesopelagic species, represented mainly by Pasiphaea multidentata and Pasiphaea sivado, carried out vertical migrations, more clearly distinguishable in smaller individuals. Diel behaviour tended to differ inside and outside the canyon, and possible causes are mainly discussed in the light of the morphology and feeding ecology of the species considered.

Population dynamics of Tenagomysis tasmaniae Fenton, Anisomysis mixta australis (Zimmer) and Paramesopodopsis rufa Fenton from south-eastern Tasmania (Crustacea:Mysidacea)

The population dynamics of a coastal mysid community was examined at One Tree Point in southern Tasmania over a 12-month period, including three 24-hour sampling sessions. Fourteen mysid species were recorded. Zonation patterns, life-history and diel activity of the three most abundant species, Tenagomysis tasmaniae, Anisomysis mixta australis and Paramesopodopsis rufa were examined. These three species were found in large numbers throughout the year associated with the macroalgal fringe on either side of the bay. Habitat partitioning within this zone of occurrence was evident. T. tasmaniae was the most abundant species (annual mean density 32.4 m−3), followed by A. mixta australis (annual mean density 20.5 m−3 ) and P. rufa (annual mean density 11.3 m−3). The major peaks of abundance of these three species were temporally separate. Breeding was intensive for the three species from spring till late autumn. A cessation of breeding in winter was evident for A. mixta australis and to a lesser extent for P. rufa but T. tasmaniae bred throughout the year although at a reduced rate during winter. Examination of the diel behaviour identified peaks of abundance at sunrise and sunset for T. tasmaniae; P. rufa was caught in greater numbers at night, but no consistent pattern was observed for A. mixta australis.

Comparison of Beam Trawls for Sampling Macrofauna of Posidonia Seagrass

Beam trawls are a practical method for sampling vagile fauna from deep seagrass beds. The catches of fish and macroinvertebrates associated with Posidonia australis from two beam trawl designs were compared with the catch from a new design of beam trawl. Greater numbers of species and individuals of fish and macroinvertebrates were caught by the new trawl. Its catch also included almost the full range of species taken by the other two trawls. The new trawl was then trialed in the day and at night to compare differences in the catch of species between these times. Trawling at night yielded significantly more species and individuals of macroinvertebrates. In general, more fish were caught at night than during the day, but this was not the case at all sites, nor for all species. We emphasize the need for testing of sampling methods, and consideration of diel behavior patterns, when estimating abundance and species richness of macrofaunal seagrass communities.

Behavior of period-altered circadian rhythm mutants ofDrosophila in light: Dark cycles (Diptera: Drosophilidae)

Adults of Drosophila melanogasterhad their locomotor activity monitored under conditions of cycling light and dark (12 h each per cycle). The elementary behavior of wild-type flies under these “LD” conditions fluctuated between levels of high and levels of low activity. Two high-activity peaks occurred within a given cycle: one at about dawn; the other, at around dusk. Such accentuated activity levels gradually subsided to troughs in the middle of the day and of the night, after which the flies anticipated the next environmental transition by gradually becoming more active. Descriptions of these activity profiles were augmented by newly developed formal analyses of the “diel rhythm” phases (based in part on digital filterings of the raw behavioral data). The applications of these analyses led to objective, automated determination of when in the morning and the evening the flies' activity peaks occur. This normal diel behavior was compared to the locomotor activity and phase determinations for a series of rhythm variants. Most of these involved mutations at the period (per)locus and germ-line transformants bearing normal or altered forms of DNA cloned from this “clock gene.” Such genetic variants have been shown previously to exhibit, in constant darkness, strain-specific circadian periods ranging from about 19 to about 29 h. We now show that the phases of the evening peaks of activity under LD conditions were correspondingly earlier than normal for the short-period mutants and later than normal for those with long circadian cycle durations. The morning peaks, however, moved (in comparison to the normal phase position) minimally under the influence of a given pervariant.

Patterns of recruitment and resource use in a shallow-water fish assemblage in Moreton Bay, Queensland

The most abundant fish species was cardinal fish Apogon fasciatus, followed by fan-bellied leatherjacket Monacanthus chinensis, leatherjacket Paramonacanthus otisensis, trumpeter Pelates quadrilineatus and pony fish Leiognathus moretoniensis. Small juveniles of these species recruited to the area, with all except L. moretoniensis being most abundant at the most vegetated site. Mean catch rates differed significantly between sites, and patterns of habitat use, seasonality and diel behaviour varied between species. There was evidences of ontogenetic migration into deeper water in all species, although this was weakest for A. fasciatus. P. quadrilineatus and L. moretoniensis took large amounts of polychaetes and copepods, M. chinensis and P. otisensis consumed more amphipods, molluscs and vegetation, and A. fasciatus exploited a wide size range of prey, including crabs, fish and small crustacenas. Interspecific diet overlap was greater in larger fish, but was less than intraspecific overlap between size classes. Daytime feeders dominated the assemblage, but catch rates were higher at night. Overall patterns of resource use suggested species partitioning, but strong evidence of niche separation was obtained only for L. moretoniensis, which was distinct on all three major resource axes (food, habitat, time). Scope thus existed for interspecific competition between members of the assemblage. -from Authors