Autumn Growth Rates Research Articles

Seasonal similarity in rates of protistan herbivory in fjords along the Western Antarctic Peninsula

AbstractWe quantified phytoplankton growth and protistan grazing rates during late austral autumn 2013 and late austral spring 2014, in several glacio‐marine fjords and connecting channels along the Western Antarctic Peninsula (WAP). During austral autumn, low and declining chlorophyll a (Chl a) concentrations (≤ 0.4 μg L−1) were almost entirely composed of pico/nanophytoplankton, whereas during austral spring, high but patchy Chl a concentrations in the fjords (up to 18.5 μg L−1) reflected a diatom bloom. These contrasting dynamics were associated with high seasonal differences in irradiance, but not temperature, and were consistent with the balance resulting from lower phytoplankton growth rates in autumn (−0.01 d−1 to 0.19 d−1) than in spring (0.06–0.93 d−1) but similar magnitudes of herbivorous grazing in both seasons. Grazing was either absent or low (0.11–0.26 d−1) and restricted to the picophytoplankton and nanophytoplankton. In the productive fjords lining the WAP, a fraction of primary production was channelled through a persistent and across‐seasons equally active microbial food web, while during spring an increasing fraction of organic carbon shifted from trophic transfer and recycling to an export pathway.

Growth ofHimantoglossum adriaticumandH. caprinumindividuals, and relationship between sizes and flowering

The long-term protection of plant species is impossible without a comprehensive and thorough knowledge of their biology. This paper deals with some of the important aspects of the biology of two strictly protected species, Himantoglossum adriaticum and H. caprinum. The changes of the leaf area of plants were measured with a non-destructive method and the growth pattern was investigated during the vegetation period. It was also studied how the plant size of individuals changed from year to year, and what kind of connection there was between the plant condition and the flowering. Large size plants of both species were characterised by intensive growth rates in autumn and spring, their growth stopped in winter. Often they lost some of their leaf areas because of damage from insects (mainly in the case of H. caprinum) , and frost (almost exclusively in the case of H. adriaticum ). In some years the medium and small size plants were characterised by similar growth pattern to those of large size ones, but more often their growth did not stop in winter, though their growth was not so fast. The medium and small size H. caprinum individuals showed an intense autumn growth only in one vegetation period, which characterised both large size individuals of H. caprinum and all individuals of H. adriaticum. The constant annual rate of growth, which may have been slowed meaning that the leaf number did not grow, but it did not stop either, was detected in hardly more than 10% of individuals with both species. In the case of H. adriaticum the critical size for flowering seemed to be 50 cm 2 , which was usually reached in the four-leaf stage of the rosettes. The same value was 100 cm 2 in the case of H. caprinum and it needed at least a six-leaf basal rosette. The leaf number and the leaf area of reproductive plants had been larger for already two years before flowering took place, than those of the plants that remained vegetative.

Life history, growth patterns and feeding habits of two predatory stoneflies, Skwala pusilla (Perlodidae) and Kamimuria tibialis (Perlidae) in northern Japan

Life history, growth patterns and feeding habits were compared between two common predatory stream stoneflies, Skwala pusilla and Kamimuria tibialis. Both species are univoltine with the larvae appearing in the streams in summer and showing high growth rates in autumn. Skwala pusilla continued growing to the final instar during winter, and then emerged in early spring. In contrast, the growth of K. tibialis stagnated in winter and turned high again in spring when they molted to the final instar. Skwala pusilla consumed a higher proportion of algae than did K. tibialis, and a randomisation test indicated significant difference between the two species in the degree of carnivory. However, S. pusilla did not enhance the degree of carnivory in winter when the growth of K. tibialis stagnated. These results suggest that the relatively low degree of carnivory in S. pusilla is not due to interspecific competition for prey resources.

Patterns of growth in the early life history of the round herring Etrumeus teres

Early life history traits of young‐of‐the‐year (YOY) round herring Etrumeus teres, caught in Tosa Bay (south‐western Japan), were studied using otolith microstructure analysis for the 2000–2003 year classes. Hatch dates ranged from October to March, and were restricted to either autumn or winter within each year class. YOY ranged from 50 to 123 mm total length (LT) and from 57 to 192 days in age. The relationship of LT to otolith radius was linear. Individual growth rates (GI) were backcalculated between the 70th and 150th days (the size range of most YOY caught) using the biological intercept method. GI ranged from 0·3 to 1·4 mm day−1 and decreased in most cases as season progressed irrespective of year class, although GI in winter cohorts were significantly higher than in autumn cohorts. Otolith growth rates (GO) ranged from 2·13 to 12·25 μm day−1 for autumn spawned YOY and from 3·12 to 12·41 μm day−1 for YOY spawned in winter. The GO trajectories followed three consistent patterns: (1) an increase in increment widths after first feeding through the second week of larval life, then (2) a plateau in increment spacing before increment widths increased again until reaching the maximum growth rate, followed by (3) a gradual decrease in increment widths until the end of the fifth month. The three stages occurred irrespective of spawning season, although YOY spawned in October and December had higher GO during stages (1) and (2) than YOY spawned in February and March, whereas higher GO was observed for late‐winter cohorts in stage (3). Otolith growth from YOY spawned in December and January showed an intermediate pattern between YOY hatched in the early autumn (October to December) and late winter (February to March). The GO trajectories were cross‐matched to the calendar date to estimate time series of otolith growth rates (GOTS) for each year. A parabolic trend was found with maximum GOTS in autumn and spring and minimum values in winter. This trend was significantly correlated to daily sea surface temperature variations. The differences in otolith growth trajectories suggest that the otolith microstructure of E. teres may be used as a natural tag for identifying autumn and winter spawned cohorts.

A Net-Pen Experiment to Evaluate Kokanee Growth Rates in Autumn in an Oligotrophic Lake withMysis relicta

We used an in situ net-pen experiment to investigate autumn growth rates of kokanee Oncorhynchus nerka in a oligotrophic lake with introduced opossum shrimp Mysis relicta. In the 21-d experiment conducted in October, kokanee (53.9 mm average total length) were placed either in net-pens made of 1.59-mm mesh, allowing drift of ambient zooplankton into the pens, or in pens made of 153-μm mesh containing zooplankton at comparatively high, low, or very low densities relative to that of the ambient zooplankton density pens. Kokanee receiving ambient zooplankton densities grew 0.83%/d, whereas those fed the same diet at high densities grew 1.84%/d, and those fed the low and very low densities grew −0.69% and 0.17%/d, respectively. Final kokanee biomass differed significantly among treatment groups. Large growth differences also existed among treatment groups, but comparisons between the ambient and high treatments or between the ambient and very low treatments were not statistically significant. In samples collected from the lake, the copepods Cyclops bicuspidatus thomasi and Diaptomus ashlandi were the most abundant zooplankters, representing more than 70% of the samples. Kokanee growth in this study was consistent with that in other lakes with limited food resources and showed that growth of wild kokanee would have been greater in October in Lake Pend Oreille had zooplankton been more abundant.

Winter growth of juvenile plaice on the Port Erin Bay (Isle of Man) nursery ground

Juvenile plaice (Pleuronectes platessa) were studied in Port Erin Bay, Isle of Man, U.K. between September and March 1989/1990 and 1990/1991. Plaice (>90 mm) were tagged and individual growth rates calculated for the autumn, winter and over-winter time periods. During the study the population of fish >90 mm remained fairly stable both within a study season and between years. Autumn growth rates ranged from 0 to 0.39 mm day−1 (mean1989=0.13 mm day−1, mean1990=0.10 mm day −1) and winter 0 to 0.5 mm day−1 (mean1990=0.11 mm day−1 and mean1991=0.17 mm day −1). In general, growth rates were higher at higher mean seasonal temperatures. However, relative growth rate was significantly higher in the colder winter period of 1991 than 1990.

Individual growth and smoltification of juvenile masu salmon, Oncorhynchus masou Brevoort, under rearing conditions

In a reared population of individually marked juvenile masu salmon, individual growth was monitored from the first autumn in 1983 to the following spring. The potential smolts were not significantly greater in mean fork length and body weight than the potential parr in late August of the first year, but they then grew faster until March of the second year. As a result, the potential smolts formed the upper mode of the bimodal length distribution after February. Especially in autumn (October and November) the specific growth rates of potential smolts were significantly greater than those of parr, and the bimodality in growth rate distribution was more distinct for males than females. These suggest that there are two groups having different growth rates in autumn of the first year and that sufficient growth in this period may play an important role in smoltification in the following spring.

Seasonal distribution of pasture production in New Zealand XVIV. Central Taranaki

Abstract Pasture growth rates for 8 years are presented for a Stratford site, at an altitude of 311 m on the eastern ring-plain surrounding Mt Egmont. Yields were measured on grazed pasture cut with a standardised method using moveable cages. The mean yield and standard deviation over all years of measurement are given for the 2 standard cutting intervals — 14 and 28 days. The growth pattern for both cutting intervals had a spring peak, although the spring growth rates were lower but persisted longer under 14 day cutting than for 28 day cutting, and a marked winter depression occurred from June to August. The mean annual yield was 12 030 kg DM/ha under 28 day cutting, and 9 940 kg DM/ha under 14 day cutting. On average, 41 and 36% of the annual yield was produced in the spring months for 28 and 14 day cutting intervals respectively, 31 and 32% was produced in summer months and 19 and 23% over autumn. In winter, 9% of the annual yield was grown at both cutting intervals. The onset of spring growth and maximum growth rate attained showed marked variation between years. This affects decision-making for both calving date and paddock closure for conservation. Late summer/early autumn growth rates also varied markedly reflecting the variable summer rainfall and soil moisture. The growth pattern of the Lolium perenne component was similar to that of the entire sward, reaching a peak in October/November, while Trifolium repens did not reach peak growth until December/January. General climatological data, rainfall, and mean air temperature during the period of pasture measurement are given.

Seasonal distribution of pasture production in New Zealand XVIII. South Taranaki

Abstract Pasture growth rates for 8 years are presented for a site on the Waimate plains of South Taranaki. Yields obtained from grazed permanent pasture were measured with a standardised cutting method using a moveable cage technique. Two cutting intervals were used and the mean yield and standard deviation over all years of measurement are given for standard dates at 14 and 28 day intervals. Growth rates under 28 day cutting intervals were highest in late spring and rapidly declined over summer. Autumn growth rates were reasonably constant, then declined through winter to the lowest growth rates in mid July. Fourteen day growth rates displayed a different pattern — peaking earlier in spring but at lower values — which remained reasonably constant well into summer. Autumn growth rates rose above those from late summer, and then declined in the winter months to similar values as under 28 day cutting. Forty-six per cent and 36% of annual yield occurred in the spring months for 28 and 14 day cutting interva...

Growth Rates of the Vole Microtus Townsendii during a Population Cycle

Four populations of the vole Microtus townsendii were trapped concurrently with live-traps and pitfalls from May 1976 until June 1978. Males always grew faster than females. Voles born in the spring had the highest growth rate of any season, and growth rates decreased throughout the summer and autumn. Spring growth rates of male M. townsendii less than 40 g remained constant through the population cycle, but summer and autumn growth rates became progressively less. Growth rates of males over 40 g generally declined seasonally and through the population cycle. Heavy-weight males present in peak populations gained weight throughout the preceding winter while all other males lost weight; they also grew faster than mediumweight males at all weight ranges from the increase until the peak spring. After the peak spring, heavy-weight and medium-weight males grew at similar rates, which suggests that they had different asymptotic weights during this portion of the cycle.

VI. Wairakei, pasture and lucerne production

Abstract Pasture growth rates are presented for a hill and flatland site on pumice soils at Wairakei for a 7-year period. They were obtained from grazing trials cut by a standardised cutting method at regular intervals using a movable cage technique. The mean yield and standard error of individual samples over all years of measurement are given for standard dates at 14-day intervals. The growth pattern at each site had a spring and early summer peak, a summer depression, and a smaller but more variable peak in autumn. On the flatland site spring growth and the early autumn flush were delayed compared with the hill site. The hill site had substantially higher growth rates than the flatland site. At both sites about 8% of the annual yield was produced in winter (June, July, and August), 38% in spring, 37% in summer, and 17% in autumn. Spring, summer, and autumn growth rates were more variable on the flatland site than on the hill site, but this was reversed in winter. Seasonal growth rates and annual yields...