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1.
The transparent goby Aphia minuta (Risso, 1810) is one of the main target species of the small-scale fishery off the Island of Majorca. Otolith microstructure
and length-frequency analysis were used to study the age and growth of this species during the 1982/1983 and 1992/1993 fishing
seasons. Daily periodicity of increment formation was determined by experiments with marked otoliths in individuals maintained
in captivity. The length range of the catches during the 11 yr period was between 12 and 49 mm, with a main distribution (89%)
between 24 and 40 mm. Otolith age-readings indicate that the population exploited in the commercial fishery consists of seven
age-groups (2 to 8 mo old), with a very high proportion of individuals (95%) between 3 and 6 mo old. Population growth-curves
revealed no differences between males and females. The growth parameters for the whole population are: asymptotic length,
L
∞ = 53.69 mm; growth coefficient, K = 2.23 yr−1; theoretical age at length zero, t
0 = −0.005 yr. Those individuals of A. minuta caught in Majorca during the winter period reached a maximum age of 7 or 8 mo.
Received: 30 December 1996 / Accepted: 16 April 1997 相似文献
2.
Recruitment variability plays a critical role in determining local population densities of benthic organisms, but extreme
vulnerability at the onset of juvenile life is a trait that is largely responsible for population survivorship trends. The
aim of the present study was to determine the role of juvenile recruitment in the population structure of Necora puber. Juveniles of N. puber were collected from the lower intertidal of rocky shores of Plymouth Sound (southwest coast of the UK) and monthly size–frequency
distribution were used to determine the dynamics and the growth of the population. The parameters of the von Bertalanffy growth
function were estimated (K=0.281 year−1; t
0=0.043; C=0.103; and t
s=0.268) assuming a L
∞=105 mm. Growth was markedly seasonal and present results indicated a slower juvenile growth rate than described previously
for N. puber. The recruitment period was extensive and was two times higher in 2001 than in 2000 at the start of the 1+ year, but levelled
off at the end of the 1+ year class on three of the four shores studied. Instantaneous mortality as high as 5.1 year−1(99.4% year−1) was observed during the higher recruitment year. Early juvenile mortality appears to be density dependent and a demographic
bottleneck appears to limit the number of juveniles on some shores. 相似文献
3.
In Red Wharf Bay, UK the naticid gastropod, Polinices pulchellus, was more abundant and more highly aggregated during the summer months (June–August 2001) than during the winter (December 2000). Whilst small numbers of juvenile P. pulchellus (4–6 mm shell length) were present throughout the year the population consisted mainly of individuals of 12–14 mm shell length. Juvenile snails grew rapidly in size during the winter and early spring; growth then virtually ceased between May and June, following which there was a further period of rapid growth between August and February. Densities ranged between 57 and 4,073 ha−1 and the largest individual collected during this investigation measured 16.2 mm in shell length. Statoliths from adult P. pulchellus revealed the presence of a settlement ring and two prominent growth rings (rings 1 and 2). A curvilinear relationship exists between statolith diameter and shell length in snails up to 16 mm in length. Settlement rings ranged in diameter from 19.7 to 45.2 μm (mean 29.8 μm; SE=0.41) giving an estimated shell length of the settled juvenile of 1.1 mm. The diameter of ring 1 and ring 2 were significantly correlated indicating that rapid growth during the first year is maintained during year 2. Shell lengths estimated from the diameters of the prominent statolith rings and those obtained from length frequency data analysis (LFDA), were broadly congruent strongly suggesting an annual periodicity to the statolith rings. The largest snails (>15 mm) present within this population were estimated to be between 2 and 3 years old. Von Bertallanfy seasonal growth curves obtained from the LFDA predicted values of L∞, K and t
0 of 14.32 mm, 1.54 and −0.14 years, respectively, suggesting that P. pulchellus rapidly attains its maximum asymptotic size. 相似文献
4.
The growth rates of two fish species, the winter flounder Pseudopleuronectes americanus (Walbaum) (19.3 to 42.6 mm total length, TL) and the tautog Tautogaonitis (Linnaeus) (23.9 to 55.9 mm TL), were used to evaluate habitat quality under and around municipal piers in the Hudson River
estuary, USA. Growth rates were measured in a series of 10 d field caging-experiments conducted at two large piers in the
summers of 1996 and 1997. Cages (0.64 m2) were deployed along␣transects that stretched from underneath the piers to beyond them, encompassing the pier edge (the transitional
zone between the pier interior and the outside). Growth in weight (G
w
) was determined at five locations along the transect, 40 m beneath the pier, 20 m beneath the pier, at the pier edge, 20 m
beyond the pier edge, and 40 m beyond. Under piers, mean growth rates of winter flounder and tautogs were negative (xˉG
W
= −0.02 d−1), and rates were comparable to laboratory-starved control fishes (xˉG
W
= −0.02 d−1). In contrast, mean growth rates at pier edges and in open waters beyond piers were generally positive (xˉG
W
ranged from −0.001 to +0.05 d−1), with growth at pier edges often being more variable and less rapid than at open-water sites. Analyses of stomach contents
upon retrieval of caged fishes revealed that dry weights of food were generally higher among fishes caged at open-water stations
(xˉ range = 0.02 to 0.72 mg dry wt) than at pier-edge (xˉ range = 0.01 to 0.54 mg) or under-pier (xˉ range = 0.03 to 0.11 mg) stations, although it was apparent that benthic prey were available at all stations on the transect.
Our results indicate poor feeding conditions among fishes caged under piers, and suboptimal foraging among fishes caged at
pier edges. Inadequate growth rates can lead to higher rates of mortality, and, based on these and other earlier experiments,
we conclude that under-pier environments are poor-quality habitats for some species of juvenile fishes.
Received: 12 March 1998 / Accepted: 9 November 1998 相似文献
5.
M. Peharda C. A. Richardson I. Mladineo S. Šestanović Z. Popović J. Bolotin N. Vrgoč 《Marine Biology》2007,151(2):629-638
Age, growth and population structure of Modiolus barbatus from Mali Ston Bay, Croatia were determined using modal size (age) classes in length frequency distributions, annual pallial
line scars on the inner shell surface, internal annual growth lines in shell sections of the middle nacreous layer and Calcein
marked and transplanted mussels. The length frequency distributions indicated that M. barbatus attain a length of ∼40 mm in 5–6 years indicating that a large proportion of the population in Mali Ston Bay is <5 years
old. Some mussels of ∼60 mm were predicted to be 14 years old using the Von Bertalanffy growth (VBG) equation. Up to the first
6 pallial line scars were visible in young (<6 years) mussels but in older shells the first scars became obscured by nacre
deposition as the mussel increased in length and age. The age of the older shells (>6 years) was determined from the middle
nacreous lines in shell section, which formed annually in winter between February and March; the wider dark increments forming
during summer (June to September). The oldest mussel, determined from the middle nacreous lines, was >12 years, with the majority
of mussels aged between 3 and 6 years of age. The ages of mussels ascertained using the growth lines were not dissimilar to
the ages predicted from the length frequency distributions. Age at length curves produced using modal size class data were
not different from the data obtained using the pallial scar rings and internal growth lines. Taken together these data suggest
that M. barbatus attains a length of 40 and 50 mm within 5 and 8 years, respectively. Eighty one percent of individual M. barbatus injected with a Calcein seawater solution (300 mg Calcein l−1), into their mantle cavity successfully deposited a fluorescent line, which was visible in suitably prepared shell sections
under ultra violet light. Incorporation of Calcein into the mussel shells was seasonally variable with the lowest frequency
of incorporation in mussels marked in February and recovered in May. Seasonal shell growth was observed with significantly
higher growth rates in mussels marked in May and removed in August (ANCOVA, F
3,149 = 23.11, P < 0.001). Mussels (∼18 to 22 mm) marked in May and recovered in August displayed maximal growth rates of >2.5 mm month−1 compared with a mean mussel growth rate of 1.2 ± 0.6 mm month−1. At other times of the year mussel shell growth ranged from immeasurable to 1.48 mm month−1. 相似文献
6.
Growth rates were determined for copepodites of the genera: Acartia, Centropages, Corycaeus, Oithona, Paracalanus, Parvocalanus and Temora in nearshore waters of Jamaica from in situ microcosm incubations. At these high local temperatures (∼28 °C), total copepodite
development time was as short as 4 to 5 d. Mean instantaneous growth rates (g) ranged from as high as 1.2 d−1 to as low as 0.1 d−1. In general, cyclopoid copepods appeared to grow more slowly than calanoids of the same size. Enhancement of resources by
nutrient addition caused a 32% increase in growth rates in experiments from a mesotrophic site, but only a 17% increase at
a more eutrophic site. Additionally, copepodites at both sites showed faster development and generally larger size at stage
in response to nutrient addition. Growth rates were positively related to chlorophyll concentration in the >2 μm size-fraction.
A significant relationship of growth rate to body size (r
2 = 0.45) emerged across a wide range of trophic status, but it was confounded with resource availability. It appears that
growth in tropical copepod copepodites may be frequently limited by resources in a size-dependent manner.
Received: 30 May 1997 / Accepted: 13 May 1998 相似文献
7.
Increments in the hard parts of marine organisms (otoliths, skeletons, shells) can provide long-term chronologies of growth
analogous to tree rings. For the first time in the Southern Hemisphere, we use a dendrochronological (tree-ring analysis)
approach to develop a multidecadal chronology of growth for a temperate reef fish, Girella tricuspidata, from the coast of northern New Zealand. Growth patterns in the otoliths of this species were strongly synchronous among individual
fish over a period spanning 27 years (1980–2006). We then compared our otolith chronology to climatic records and found strong
positive correlations of growth with sea surface temperature, and weak negative correlations with the multivariate El Nino
Southern Oscillation (ENSO) index. Strongest correlations were found between summer sea surface temperature and otolith growth.
This relationship was consistent across all years and explained 44 % of the variation (y = −2.0 + 0.1785 × temperature, r
2 = 0.4367, P = 0.0002) in the G. tricuspidata growth chronology. Our study illustrates how otolith chronologies provide remarkable records of annual growth patterns over
decadal time scales that will be useful for forecasting the likely effects of climate change on marine ecosystems. 相似文献
8.
Chemical composition and growth indices in leptocephalus larvae 总被引:3,自引:3,他引:0
Leptocephali grow at extremely high rates (>1 mm d−1), but, unlike most fish larvae, leptocephali may remain in the plankton as larvae for several months before metamorphosing
into the juvenile form. During their planktonic phase, leptocephali accumulate energy reserves in the form of glycosaminoglycans
which are then expended along with lipid reserves to fuel metamorphosis. Otolith growth rates were determined using scanning
electron microscopy for four species of leptocephali common in the Gulf of Mexico, Paraconger caudilimbatus (Poey, 1867), Ariosoma balearicum (Delaroche, 1809), Gymnothorax saxicola (Jordan and Davis, 1891), and Ophichthus gomesii (Castelnou, 1855). Proximate composition, RNA:DNA ratios and protein growth rates were examined with respect to mass, length
and age. The leptocephalus growth strategy was strongly reflected in the growth indices. Mass (Y) in all four species increased with increasing age (X) according to the equation Y = aX
b
, where a is a species-specific constant and 1.05 < b < 2.40. The accumulation of acellular mass was evident in protein growth rates and RNA:DNA ratios, and was observed as a
shift in increasing size from rapid growth in length to a greater increase in mass with age. These results suggest that the
proportion of actively metabolizing tissue declines with size and is replaced by the metabolically inert energy depot: the
glycosaminoglycans. Leptocephali can thus grow to large size very rapidly with minimal metabolic penalty, an unusual and successful
developmental strategy.
Received: 27 December 1999 / Accepted: 8 June 2000 相似文献
9.
Determination of basic population parameters in long-lived Crustacea is hindered by a lack of appropriate methods for age
determination. This study uses the pigment lipofuscin as an age marker in the common Antarctic decapod Notocrangon antarcticus (Pfeffer, 1887) from the eastern Weddell Sea. Resin brain sections of the lateral somacluster of the olfactory lobe of 189
specimens were digitally recorded by confocal microscopy and images were subsequently analyzed. A modal progression analysis
of the lipofuscin concentration–frequency distribution revealed a total of eight regularly spaced modes presumed to reflect
consecutive annual age classes. All eight modes contained females, and the first four contained males. No regular modes were
obvious in the comparable length-frequency distribution. The average yearly pigment accumulation was nearly linear and estimated
as 0.02% area fraction year−1, which is considerably lower than rates published for species from lower latitudes. This is probably explained by the effect
of low water temperature on metabolism and lipofuscin accumulation rate. The growth parameters CL∞ and k from the von Bertalanffy growth function were 22.3 mm and 0.79 year−1 for females, respectively, and 16.9 mm and 0.64 year−1 for males, respectively. Mortality, estimated from catch curves, amounted to 0.44 year−1 in females and 0.92 year−1 in males, whereas P/B, calculated from the mass specific growth rate method, was slightly lower. The results indicate that the lipofuscin-inferred
population parameters are an improvement over what can be learned about N. antarcticus with traditional methods.
Received: 1 August 2000 / Accepted: 21 September 2000 相似文献
10.
Growth rates and development times were determined for nauplii of the genera: Acartia, Centropages, Corycaeus, Oithona, Paracalanus, Parvocalanus and Temora in nearshore waters of Jamaica from in situ microcosm incubations. At these high local temperatures (∼28 °C), total naupliar
development time was short: 3 to 4 d inshore and 4 to 5 d offshore. Mean instantaneous growth rates (g) ranged from as high as 0.90 d−1 for Parvocalanuscrassirostris to as low as 0.41 d−1 for Corycaeus spp. In general, nauplii of cyclopoid copepods appeared to grow more slowly than those of calanoids of the same size. Naupliar
growth rates were significantly related to body size (r
2 = 0.43 to 0.50), but were unrelated to chlorophyll concentration in any measured size-fraction. This suggests that nauplii
are generally not limited by resources, but are growing at their maximum temperature and size-dependent rates.
Received: 30 May 1997 / Accepted: 13 May 1998 相似文献
11.
Analysis of the isotope composition of calcareous structures of marine organisms has proved useful in providing biological
data. The present study constitutes the first detailed work undertaken on the isotope composition of coleoid cephalopods.
We analysed the carbon- and oxygen-isotope composition [δ13C (CO2−
3) and δ18O (CO2−
3), respectively] of the cuttlebone aragonite of wild and cultivated specimens of Sepia officinalis Linnaeus, 1758. δ13C (CO2−
3) ranged from −2.94 to 1.00‰, δ18O (CO2−
3) from −0.18 to 2.08‰. The carbon-isotope composition is not in equilibrium with the carbon species of the ambient seawater,
and does not reflect the deposition of CaCO3 in seawater. The potential influence of environmental factors and biological processes on the carbon-isotope composition
of the cuttlebone is discussed. In contrast to δ13C, the oxygen-isotope composition of cuttlebone aragonite appears to be in isotopic equilibrium with the ambient seawater.
Seasonal changes in isotopic temperature revealed by our analyses agreed with changes in the temperature of the ambient seawater.
CaCO3 was deposited all year round. A maximum life span of 2 yr, a year-round spawning season, and variable growth rates among and
within individuals have been inferred from the isotopic temperatures.
Received: 14 April 1998 / Accepted: 26 November 1998 相似文献
12.
Seasonal changes in catch rate, growth and mortality of Nassarius reticulatus from an intertidal lagoon and a wave-exposed beach at Rhosneigr (Anglesey, North Wales, UK) are described. The number of N. reticulatus caught in baited traps from the lagoon was significantly higher (>125 individuals trap−1) during the summer (>18°C), than at <12°C (<65 individuals trap−1), and the numbers caught in the lagoon were an order of magnitude greater than on the beach, >13 individuals trap−1 in July (>16°C), and <5 individuals trap−1 between December and April (<9.5°C). Predictions of shell growth attained by N. reticulatus annually in the lagoon using graphical modal progression analysis (MPA) of length frequency data, were similar to the growth
of marked and recaptured lagoon N. reticulatus. Predictions of shell growth using computerised length frequency distribution analysis (LFDA), however, did not reflect the
growth as accurately as MPA. Modal progression analysis demonstrated that N. reticulatus from the lagoon achieved a higher asymptotic maximum shell length (L
∞) and a lower growth constant (K) than animals from the beach. Shell growth was seasonal with growth of the lagoon individuals slowing down towards the end
of September and resuming in early April, about a month later than the beach individuals. Mortality of N. reticulatus was greater during the summer, and survival was lower in the lagoon than on the beach. Recruitment patterns were similar in
the lagoon and on the beach, and MPA and LFDA predicted that larval N. reticulatus settled between late summer and early autumn, with juveniles (7–8.9 mm) appearing in the population the following year, between
February and April. Growth of male and female N. reticulatus in the laboratory was similar and was temperature and size dependent. The different growth patterns between N. reticulatus from the two habitats, predicted using MPA, were maintained when individuals were reared under laboratory conditions for ∼6 months;
N. reticulatus <21 mm from the beach grew faster than individuals from the lagoon, although N. reticulatus >21 mm from the lagoon grew faster and attained a larger length (26 mm) than individuals from the beach (24 mm). Low food
availability did not affect N. reticulatus survival in the laboratory but significantly suppressed shell growth. 相似文献
13.
Ammonium concentrations of ∼1 M are commonly cited as being the threshold for inhibition of NO3
− uptake, but the applicability of this threshold to phytoplankton from different taxonomic classes has rarely been examined.
Additionally, little is known about the influence of environmental variables (e.g. growth temperature) on the interaction
between ambient NH4
+ and NO3
− uptake. Four species of estuarine phytoplankton, two diatom [Chaetoceros sp., and Thalassiosira weissflogii (Grunow) Fryxell et Hasle] and two dinoflagellate [Prorocentrum minimum (Pavillard) Schiller, and Gyrodinium uncatenum Hulburt], were grown on NO3
− at several different temperatures (4, 10, 15, or 20 °C), and the impact of NH4
+ additions on NO3
− uptake/assimilation (non-TCA-extracted) and assimilation (TCA-extracted) was assessed. For all species at all temperatures,
NO3
− uptake/assimilation and assimilation rates decreased in a roughly exponential manner with increasing NH4
+ concentrations but were not completely inhibited even at elevated NH4
+ concentrations of 200 μM. Estimated half-inhibition concentrations (K
i) were significantly greater in the diatom species (mean ± SE; 2.70 ± 0.67 μM) than in the dinoflagellate species (1.26 ± 0.55 μM). Half-inhibition constants were positively related to temperature-limited relative growth rate although not significantly.
The observed inhibition of NO3
− uptake and assimilation, as a percentage of NO3
− uptake in the absence of NH4
+, averaged about 80% and ranged from 49 to 100%. For all species, a significant (P < 0.001) positive correlation was found between percent inhibition of NO3
− assimilation and temperature-limited relative growth rate. Two experiments on Chesapeake Bay phytoplankton during an April
1998 diatom bloom showed that in short-term (∼1 h) temperature manipulation experiments, percent inhibition of NO3
− uptake/assimilation was also positively related (P = 0.05) to experimental temperature. The observed relationships between temperature-limited relative growth rate and percent
inhibition of NO3
− assimilation rates for the species tested suggest that at the enzyme level, the inhibitory mechanism of NO3
− assimilation is similar among species, but at the whole cell level may be regulated by species-specific differences in the
accumulation of internal metabolites. These findings add not only to our understanding of species-specific variability and
the role of growth temperature, but also provide additional data with which to evaluate current models of NH4
+ and NO3
− interactions.
Received: 31 August 1998 / Accepted: 7 December 1998 相似文献
14.
The euphausiids Thysanoessa inermis (Kroyer 1846), Thysanoessa spinifera (Holmes 1900), and Euphausia pacifica (Hansen 1911) are key pelagic grazers and also important prey for many commercial fish species in the Gulf of Alaska (GOA).
To understand the role of the euphausiids in material flows in this ecosystem their growth rates were examined using the instantaneous
growth rate (IGR) technique on the northern GOA shelf from March through October in 2001–2004. The highest mean molting increments
(over 5% of uropod length increase per molt) were observed during the phytoplankton bloom on the inner shelf in late spring
for coastal T. inermis, and on the outer shelf in summer for T. spinifera and more oceanic E. pacifica, suggesting tight coupling with food availability. The molting rates were higher in summer and lower in spring, for all species
and were strongly influenced by temperature. Mean inter-molt periods calculated from the molting rates, ranged from 11 days
at 5°C to 6 days at 8°C, and were in agreement with those measured directly during long-term laboratory incubations. Growth
rate estimates depended on euphausiid size, and were close to 0 in early spring, reaching maximum values in May (0.123 mm day−1 or 0.023 day−1 for T. inermis) and July (0.091 mm day−1 or 0.031 day−1 for T. spinifera). The growth rates for E. pacifica remained below 0.07 mm day−1 (0.016 day−1) throughout the season. The relationship between T. inermis weight specific growth rate (adjusted to 5°C) and ambient chlorophyll-a concentration fit a Michaelis–Menten curve (r
2 = 0.48) with food saturated growth rate of 0.032 day−1 with half saturation occurring at 1.65 mg chl-a m−3, but such relationships were not significant for T. spinifera or E. pacifica. 相似文献
15.
Effects of low dissolved oxygen on early development and swimming behaviour of veliger larvae of the scavenging gastropod
Nassarius festivus were studied. Embryonic development was significantly delayed when dissolved oxygen level was reduced to 3.0 mg O2 l−1 and no embryo hatched successfully at 0.5 mg O2 l−1. Veliger larvae hatched at 4.5 mg O2 l−1 had significantly smaller velar lobe, shell length and shell width. Median 48-h LC50 value of the veliger larvae was estimated at 1.25 mg O2 l−1 with lower swimming speed (swimming velocity and dispersal velocity) being recorded for the survivors exposed to reduced
oxygen levels. The percentage of veliger larvae that developed into crawling juveniles was significantly reduced and metamorphosis
was delayed at 4.5 mg O2 l−1 whereas all larvae at 3.5 mg O2 l−1 died before they underwent metamorphosis. Juveniles developed at 4.5 mg O2 l−1 were also smaller than those at 6.0 mg O2 l−1. Results indicated that dissolved oxygen levels well above hypoxia levels (2.8 mg O2 l−1) have already had significant impact on the hatching success and larval development in gastropods, which may lead to long-term
decreases in population growth. 相似文献
16.
G. D’Onghia L. Sion P. Maiorano Ch. Mytilineou S. Dalessandro R. Carlucci S. Desantis 《Marine Biology》2006,149(3):435-446
The population biology and life strategies of Chlorophthalmus agassizii were studied in the Ionian Sea (eastern–central Mediterranean) using the data collected during the experimental trawl surveys carried out from 1995 to 2000. Depth-related trends of both density and size were found. With depth the former decreased while the latter increased. A typical bigger–deeper phenomenon was detected: young-of-the-year individuals occur on the shelf during autumn–winter months and move towards bathyal bottoms as they grow. The sampled population was made up of several size–age groups. The maximum age of 8 years was identified by means of otolith readings. The Von Bertalanffy growth parameters were estimated from the age–length key (L
∞=189.04±5.401 mm; k=0.24±0.021; t
o=−1.20±0.132; φ′=3.94) and modal progression analysis (L
∞=218.33±18.397 mm; k=0.164±0.028; t
o=−1.694±0.171; φ′=3.89). Reproduction of this monoecious fish was observed during summer–early autumn. Considering the female portion of the gonad, the size at attainment of 50% maturity was 115 mm TL. The corresponding age is within the third year of life. The simultaneous occurrence of oocytes in different development stages was shown in the ovary. Both the asynchronous ovary and oocyte size distribution indicate that C. agassizii spawns more than once during a reproductive season (batch spawner). Functional fecundity (on average 3,018 hydrated oocytes) was between 37 and 69% of the absolute fecundity and increased significantly with the individual size. Since adult specimens are mostly distributed on the slope, eggs and larvae develop in epipelagic waters and migrate in-shore where juvenile forms recruit on the shelf. Juveniles migrate ontogenetically towards deeper bottoms and after 2–3 years start to reproduce annually within a life span greater than 10 years. 相似文献
17.
Size and temperature-dependent variations in intermolt duration and size increment at molt of Northern Shrimp, Pandalus borealis 总被引:1,自引:0,他引:1
Growth of Pandalus borealis post-larval stages was measured in relation to size and temperature. Growth characteristics, including intermolt period (IP),
molt increment (MI) in size and mass, and tissue allocation in juvenile, male, and female shrimp, were evaluated at 2, 5,
and 8°C, the temperature range where this species is generally found in the Northwest Atlantic. Significant variations in
growth were associated with temperature and shrimp size. IP (days) increased significantly with shrimp size and was inversely
related to temperature. Size (cephalothorax length in mm) and temperature effects were best described by IP = 10(0.67 log(CL) − 0.06 T − 1.34). The pronounced effect of temperature on IP while MIS changed little indicated that the main influence of temperature on growth rate of P. borealis was through IP. Specific growth rate (SGRS) decreased rapidly with size to near zero values in females. Overall, juveniles were much more sensitive to temperature variations
than adults, suggesting that temperatures encountered during the juvenile stage will largely influence the growth trajectory
of the population. 相似文献
18.
This study analyzed the isotopic profiles of four aragonitic shells of Scrobicularia plana in conjunction with measured seawater temperatures and salinities. Comparison of δ18OSHELL with expected values revealed fractionation of δ18O in near equilibrium with the ambient environment. Growth cessation occurred between November and March. Carbonate deposition
stopped when temperatures were <12°C. Analysis of δ13CSHELL values suggested that carbon in the shell does not reflect the DIC in ambient water, likely due to the incorporation of metabolic
carbon. An ontogenetic trend of increasing δ13C values over time was observed, likely related to changes in metabolic activity. Annual growth patterns were inferred from
δ18OSHELL profiles and compared with internal and external growth lines. Estimations of age based on external lines were unreliable,
resulting in overestimation of age and underestimation of growth rates, likely due to the disturbance lines being wrongly
identified as annual. Analysis of internal lines may lead to over- or underestimation of age and was more reliable in recent
portions of the shell. 相似文献
19.
The population dynamics of Pseudocalanus acuspes in the Central Baltic Sea were studied from March 2002 to May 2003 on a monthly basis. All stages were present year round
with a stage shift from nauplii to older copepodite stages over the course of the year. Biomass, estimated from prosome length,
peaked between May and September with maximum recorded values of 594 and 855 mg C m−2 in May 2002 and 2003, respectively. Differences in biomass between stations up to a factor of 20 were observed especially
in April/May and October. Mean egg production rate (EPR) showed a seasonal course and was highest in April 2002 and 2003 with
3.6 and 2.1 eggs f−1 day−1, respectively, corresponding to a mean weight-specific egg production rate (SEPR) of 0.13 and 0.04. Egg production seems
to be limited by food from May on. Stage durations determined from moulting experiments turned out to be extremely long. Maximum
growth rates based on stage durations of 15–25 days at 4°C in May and July 2003 amounted for 0.03–0.05 day−1 in CI-CIV. Comparing these rates with rates derived from temperature–development relationships for P. acuspes from the literature resulted in five times higher growth rates for the latter case. Secondary production reached values up
to 9.1 mg C m−2 day−1 (method for continuously reproducing populations) and 10.5 mg C m−2 day−1 (increment summation). 相似文献
20.
The mangrove channels of Bahía Magdalena, Mexico, are important developmental areas for juvenile green, or black turtles (Chelonia mydas), but incidental bycatch and illegal hunting threaten population persistence. We studied size distribution, condition index
(CI), growth rates, and mortality of black turtles in Estero Banderitas, the largest mangrove channel in Bahía Magdalena,
to supply information for the development of effective conservation strategies. A total of 213 black turtles (including 88
recaptures) were caught in entanglement nets between July 2000 and July 2003. Average yearly catch per unit of effort (CPUE,
1 unit: 100 m of net fishing for 12 h) dropped during the study from 2.19 to 0.76. About 97% of all turtles were considered
juveniles, average size was 54.6 ± 9.5 cm. Turtles were significantly smaller at the head of Estero Banderitas than in the
central part of the Estero and in the open bay, indicating size-based habitat segregation. Average growth rate was 1.62 cm/year
and declined with increasing size. Growth was seasonal and three times higher in summer (0.28 cm/month) than in winter (0.09 cm/month),
body CI was also significantly higher during the summer months. A seasonalized von Bertalanffy growth function (VBGF) was
used to model growth for the size range studied (43–73 cm SCL), with the parameters: L
∞ = 101 cm SCL; K = 0.04 year−1; t
0 = 0; C = 0.4 and t
s = 0.75. Growth data indicate that black turtles may spend up to 20 years in Bahía Magdalena before they reach maturity at
about 77 cm SCL. The total mortality estimate (Z) from the length converted catch curve was 0.16, corresponding to a yearly survival probability of 0.85. 相似文献