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1.
The habitat experienced during early life-history stages can determine the number and quality of individuals that recruit
to adult populations. In a field experiment, biogenic habitat complexity was manipulated (presence or absence of foliose macroalgae)
at two depths (2–3 m and 5–6 m) and the habitat-dependent effects on recruitment of the black foot abalone (Haliotis iris) were examined at three field sites along the south coast of Wellington, New Zealand (41°20′S, 174°47′E), between July and
November 2005. Recruit density (<5 weeks post-settlement) was measured on cobbles covered with crustose coralline algae. Habitats
of low complexity (barrens treatments) had consistently greater densities of recruits than habitats of high complexity (algae
treatments). However, recruits in algae habitats were larger, and for deep habitats, there was greater survival in algae habitats
compared with barrens habitats. While depth had no significant effect on early recruit (<2 weeks post-settlement) density,
late recruit (<5 weeks post-settlement) density was greater in shallow habitats, and so it seems recruit survival was greater
in shallow habitats. In this experiment, algal habitat complexity had strong effects on early recruit abundance, but habitat-dependent
variations in recruit growth and survival may modify initial patterns of abundance and determine recruitment to adult abalone
populations. 相似文献
2.
Arthur R. Bos Girley S. Gumanao Marieke M. van Katwijk Benjamin Mueller Marjho M. Saceda Rosie Lynn P. Tejada 《Marine Biology》2011,158(3):639-648
Archaster typicus, a common sea star in Indo-Pacific regions, has been a target for the ornamental trade, even though little is known about
its population biology. Spatial and temporal patterns of abundance and size structure of A. typicus were studied in the Davao Gulf, the Philippines (125°42.7′E, 7°0.6′N), from February 2008 to December 2009. Specimens of
A. typicus were associated with intertidal mangrove prop roots, seagrass meadows, sandy beaches, and shoals. Among prop roots, specimens
were significantly smaller and had highest densities (131 ind. m−2) between November and March. High organic matter in sediment and a relatively low predation rate seemed to support juvenile
life among mangroves. Size and density analyses provided evidence that individuals gradually move to seagrass, sandy habitats,
and shoals as they age. Specimens were significantly larger at a shoal (maximum radius R = 81 mm). New recruits were found between August and November in both 2008 and 2009. Timing of recruitment and population
size frequencies confirmed a seasonal reproductive cycle. Juveniles had relatively high growth rates (2–7 mm month−1) and may reach an R of 20–25 mm after 1 year. Growth rates of larger specimens (R > 30 mm) were generally <2 mm month−1. The activity pattern of A. typicus was related to the tidal phase and not to time of day: Specimens moved over the sediment surface during low tides and were
burrowed during high tides possibly avoiding predation. This is one of the first studies to document an ontogenetic habitat
shift for sea stars and provides new biological information as a basis for management of harvested A. typicus populations. 相似文献
3.
The horned sea star (Protoreaster nodosus) is relatively common in the Indo-Pacific region, but there is little information about its biology. This study of the population
biology of P. nodosus was carried out in Davao Gulf, The Philippines (7°5′N, 125°45′E) between September 2006 and May 2008. Protoreaster nodosus was found in sand and seagrass dominated habitats at a mean density of 29 specimens per 100 m2 and a mean biomass of 7.4 kg per 100 m2, whereas a significantly lower density and biomass was found in coral and rock dominated habitats. Adult specimens (mean
radius R = 10.0 cm) were found at depths of 0–37 m, whereas juveniles (R < 8 cm) were only found in shallow sandy habitats with abundant seagrass (water depth ≤2 m). Increased gonad weights were
found from March to May (spawning period), which coincided with an increasing water temperature and a decreasing salinity.
Density and biomass did not change significantly during reproduction, but sea stars avoided intertidal habitats. All specimens
with R > 8 cm had well developed gonads and their sex ratio was 1:1. Protoreaster nodosus grew relatively slowly in an enclosure as described by the exponential function G = 7.433 e−0.257 × R
. Maturing specimens (R = 6–8 cm) were estimated to have an age of 2–3 years. Specimens with a radius of 10 cm (population mean) were calculated
to have an age of 5–6 years, while the maximum age (R = 14 cm) was estimated as 17 years. Potential effects of ornamental collection on the sea star populations are discussed.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
Understanding physiological and environmental variables that initiate sexual maturity would provide fundamental information
on life history dynamics. The aim of this study was to test the usefulness of the common circumnuclear ring (CNR), an oocytic
structure similar to the Balbiani body, which appears just prior to oocyte development as a predictor of first maturation
in Atlantic herring (Clupea harengus). The relative roles of physiology (e.g. fat) and photoperiod as triggers of maturation were also investigated. Samples were
collected in May 2008 (72°26′–73°84′N/11°26′–18°40′E) and February 2009 (56°12′–59°45′N/00°25′–03°06′W). These data suggested
that thresholds in body size may influence the decision to mature. We also found that short days (winter solstice) may be
the photoperiod trigger for a first-decision window for both Norwegian spring-spawning (NSS) and North Sea autumn-spawning
(NSAS) herring. The second-decision window for NSAS herring maturation appears to be triggered by longer days (spring equinox),
while a decreasing rate of day lengthening may trigger NSS herring maturation. So, photoperiodic cycle is a key determinate
of the timing of maturation in Atlantic herring. 相似文献
5.
Giant clams form a symbiosis with photosynthetic algae of the genus Symbiodinium that reside in clam mantle tissue. The allometry of symbiont photosynthetic performance was investigated as a mechanism for
the increasing percentage of giant clam carbon respiratory requirements provided by symbionts as clam size increases. Chlorophyll
fluorescence measurements of symbionts of the giant clam Tridacna maxima were measured during experiments conducted in September of 2009 using specimens 0.5–200 g tissue wet weight (3–25 cm long),
collected from waters around southern Taiwan (N 21°36′, E 120°47′) from July to August of 2009. Light-dependent decreases
in effective quantum yield (∆F/F
m′) calculated as the noontime maximum excitation pressure over PSII (Q
m), relative electron transport rates (rETR), and dark-adapted maximum quantum yield (F
v/F
m) all varied as a quadratic function of clam size. Both Q
m and rETR increased as clam size increased up to ~10–50 g then decreased as clam size increased. F
v/F
m decreased as clam size increased up to ~5–50 g then increased as clam size increased. Chlorophyll fluorescence measurements
of rETR were positively correlated with gross primary production measured during chamber incubations. Overall, symbionts of
mid-sized clams ~5–50 g exhibited the highest light-dependent decreases in effective photosynthetic efficiencies, the highest
relative electron transport rates, and the lowest maximum photosynthetic efficiencies, and symbiont photosynthetic performance
is allometric with respect to host clam size. 相似文献
6.
A bottom-mounted upward-facing 38-kHz echo sounder was deployed at ~400 m and cabled to shore in Masfjorden (~60°52′N, ~5°24′E), Norway. The scattering layers seen during autumn (September–October) 2008 were identified by trawling. Glacier lanternfish
(Benthosema glaciale) were mainly distributed below ~200 m and displayed three different diel behavioral strategies: normal diel vertical migration
(NDVM), inverse DVM (IDVM) and no DVM (NoDVM). The IDVM group was the focus of this study. It consisted of 2-year and older
individuals migrating to ~200–270 m during the daytime, while descending back to deeper than ~270 m during the night. Stomach
content analysis revealed increased feeding during the daytime on overwintering Calanus sp. We conclude that visually searching glacier lanternfish performing IDVM benefit from the faint daytime light in mid-waters
when preying on overwintering Calanus sp. 相似文献
7.
Peter J. Edmunds 《Marine Biology》2012,159(10):2149-2160
I tested the hypothesis that high pCO2 (76.6 Pa and 87.2 Pa vs. 42.9 Pa) has no effect on the metabolism of juvenile massive Porites spp. after 11 days at 28 °C and 545 μmol quanta m−2 s−1. The response was assessed as aerobic dark respiration, skeletal weight (i.e., calcification), biomass, and chlorophyll fluorescence. Corals were collected from the shallow (3–4 m) back reef of Moorea, French Polynesia (17°28.614′S, 149°48.917′W), and experiments conducted during April and May 2011. An increase in pCO2 to 76.6 Pa had no effect on any dependent variable, but 87.2 Pa pCO2 reduced area-normalized (but not biomass-normalized) respiration 36 %, as well as maximum photochemical efficiency (F v/F m) of open RCIIs and effective photochemical efficiency of RCIIs in actinic light (∆F/); neither biomass, calcification, nor the energy expenditure coincident with calcification (J g−1) was effected. These results do not support the hypothesis that high pCO2 reduces coral calcification through increased metabolic costs and, instead, suggest that high pCO2 causes metabolic depression and photochemical impairment similar to that associated with bleaching. Evidence of a pCO2 threshold between 76.6 and 87.2 Pa for inhibitory effects on respiration and photochemistry deserves further attention as it might signal the presence of unpredictable effects of rising pCO2. 相似文献
8.
A. A. Keller C. Taylor C. Oviatt T. Dorrington G. Holcombe L. Reed 《Marine Biology》2001,138(5):1051-1062
The seasonal productivity cycle and factors controlling annual variation in the timing and magnitude of the winter–spring
bloom were examined for several locations (range: 42°20.35′–42°26.63′N; 70°44.19′–70°56.52′W) in Boston Harbor and Massachusetts
Bay, USA, from 1995 to 1999, and compared with earlier published data (1992–1994). Primary productivity (mg C m−2 day−1) in Massachusetts Bay from 1995 to 1999 was generally characterized by a well-developed winter–spring bloom of several weeks
duration, high but variable production during the summer, and a prominent fall bloom. The bulk of production (mg C m−3 day−1) typically occurred in the upper 15 m of the water column. At a nearby Boston Harbor station a gradual pattern of increasing
areal production from winter through summer was more typical, with the bulk of production restricted to the upper 5 m. Annual
productivity in Massachusetts Bay and Boston Harbor ranged from a low of 160 g C m−2 year−1 to a high of 787 g C m−2 year−1 from 1992 to 1999. Mean annual productivity was higher (mean=525 g C m−2 year−1) and more variable near the harbor entrance than in western Massachusetts Bay. At the harbor station productivity varied
more than 3.5-fold (CV=40%) over an 8 year sampling period. Average annual productivity (305–419 g C m−2 year−1) and variability around the means (CV=25–27%) were lower at both the outer nearfield and central nearfield regions of Massachusetts
Bay. Annual productivity in 1998 was unusually low at all three sites (<220 g C m−2 year−1) due to the absence of a winter–spring phytoplankton bloom. Potential factors influencing the occurrence of a spring bloom
were investigated. Incident irradiance during the winter–spring period was not significantly different (P > 0.05) among years (1995–1999). The mean photic depth during the bloom period was significantly deeper (P < 0.05) in 1998, signifying greater light availability with depth. Nutrients were also in abundance during the winter–spring
of 1998 with stratified conditions not observed until May. In general, the magnitude of the winter–spring bloom in Massachusetts
Bay from 1995 to 1999 was significantly correlated with winter water temperature (r
2=0.78) and zooplankton abundance (r
2=0.74) over the bloom period (typically February–April). The absence of the 1998 bloom was associated with higher than average
water temperature and elevated levels of zooplankton abundance just prior to, and during, the peak winter–spring bloom period.
Received: 3 July 2000 / Accepted: 6 December 2000 相似文献
9.
Aerial sighting surveys were conducted in 2000 to evaluate the distribution and abundance of finless porpoise Neophocaena phocaenoides in the Inland Sea of Japan. We flew 60 north–south transects (2,218 km in total) at intervals of 6.43 km over the study area
between 131°3′ and 134°59′ E. In total, 148 groups were detected by two observers. The average group size was 1.56 individuals.
The effective strip half-width of each observer was estimated to be 107 m (coefficient of variation [CV] = 8.26%). Porpoise
abundance was estimated at 7,572 individuals and the density was as low as 0.506 individuals/km2 (CV = 17.3%). The sea is among the Japanese waters with the lowest density in spite of its favorable topographical conditions.
In the western stratum of the study area, where the estimated density was 1.31 individuals/km2, we observed a relatively regular distribution. In the central-eastern stratum, which had an estimated density of 0.208 individuals/km2, we confirmed a clumped distribution that was restricted to inshore waters or near islands. No individuals were observed
in waters between 132°51′ and 133°11′E, and between 133°43′ and 133°59′E, where sand dredging and other human activities have
been active, suggesting that habitat fragmentation has occurred. 相似文献
10.
The inarticulated brachiopod, Lingula reevii Davidson (1880) is a filter-feeding invertebrate that burrows vertically in sandy or mixed sediments. Its only recorded occurrence
is from Kaneohe Bay, Oahu, Hawaii, southern Japan, and Ambon, Indonesia. Past surveys of Kaneohe Bay populations suggested
a distinct decrease in abundance following the diversion of sewage effluent from the bay in 1978/1979. In the summer of 2004
and 2007, visual surveys were conducted in areas of historical L. reevii abundance as well as in areas appearing to have suitable habitat. In 2004, approximately 2,950 m2 at 20 sites within the bay were surveyed using quantitative belt transecting methods. A maximum density of 4 Lingula/m2 was observed, a decrease from previous maximum estimates of 500 individuals/m2 (Worcester, Dissertation, Zoology Department, University of Hawai′i, pp 49, 1969) and 100 individuals/m2 (Emig, J Exp Mar Biol Ecol 52:47–61, 1981). When these 20 sites were revisited in 2007, many had fewer or no L. reevii; therefore, broader scale presence/absence surveys were conducted at 16 additional sites in the bay (also surveyed in 2004).
The highest density of L. reevii found in 2007 was 0.94 individuals/m2. The continued decline in abundance of L. reevii in Kaneohe Bay may be due, in addition to decreased organic enrichment from diversion of sewage discharge almost 30 years
ago, to the more recent reduction of suitable habitat by the invasion of mat-forming alien algae species. 相似文献
11.
Peter J. Edmunds 《Marine Biology》2009,156(9):1797-1808
This study tested the effects of acclimatization on the response of corals to elevated temperature, using juvenile massive
Porites spp. and branching P. irregularis from Moorea (W149°50′, S17°30′). During April and May 2006, corals were acclimatized for 15 days to cool (25.7°C) or ambient
(27.7°C) temperature, under shaded (352 μmol photons m−2 s−1) or ambient (554 μmol photons m−2 s−1) natural light, and then incubated for 7 days at ambient or high temperature (31.1°C), under ambient light (659 μmol photons
m−2 s−1). The response to acclimatization was assessed as biomass, maximum dark-adapted quantum yield of PSII (F
v/F
m), and growth, and the effect of the subsequent treatment was assessed as F
v/F
m and growth. Relative to the controls (i.e., ambient temperature/ambient light), massive Porites spp. responded to acclimatization through increases in biomass under ambient temperature/shade, and low temperature/ambient
light, whereas P. irregularis responded through reduced growth under ambient temperature/shade, and low temperature/ambient light. Acclimatization affected
the response to thermal stress for massive Porites spp. (but not P. irregularis), with an interaction between the acclimatization and subsequent treatments for growth. This interaction resulted from a
lessening of the negative effects of high temperature after acclimatizing to ambient temperature/shade, but an accentuation
of the effect after acclimatizing to low temperature/shade. It is possible that changes in biomass for massive Porites spp. are important in modulating the response to high temperature, with the taxonomic variation in this effect potentially
resulting from differences in morphology. These results demonstrate that corals can acclimatize during short exposures to
downward excursions in temperature and light, which subsequently affects their response to thermal stress. Moreover, even
con-generic taxa differ in this capacity, which could affect coral community structure.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
Assignment of individuals to populations based upon genetic data is an important ecological problem that requires many polymorphic
markers, often more than are available using single locus techniques. To demonstrate the utility of amplified fragment length
polymorphisms (AFLP) in studying larval dispersal and recruitment in coral populations, two sets of AFLP primers were used
to genotype colonies of the coral Agaricia agaricites Linnaeus from three widely separated geographic locations: the Bahamas (23°28′N, 75°42′W) and Key Largo, Florida (24°55′N,
80°31′W—two sites separated by 12 km) in 1995, and the Flower Garden Banks (FGB) in the Gulf of Mexico (27°55′N,93°36′W) in
1997. In addition to adult samples from each site, recruits were collected from settling plates placed on the East FGB for
1 year (1997–1998). The AFLP technique yielded 45 polymorphic markers. An analysis of molecular variance (AMOVA) showed significant
genetic differences among the four adult populations, even between the two Key Largo sites. The recruits were significantly
different from all adult populations except those from the FGB. Discriminant function analysis and the program AFLPOP were
used to assign individuals to populations. Using the adult AFLP-banding patterns to build the statistical models, both procedures
correctly assigned the majority of adults to their respective populations in simulations and assigned all but one of the recruits
to the Flower Garden population from where they were collected . The AFLP technique provides a simple and adaptable population
assignment method for studying recruitment processes in A. agaricites and other coral species.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
13.
Michael D. Arendt Albert L. Segars Julia I. Byrd Jessica Boynton Jeffrey A. Schwenter J. David Whitaker Lindsey Parker 《Marine Biology》2012,159(1):113-125
Sixteen satellite-tagged adult male loggerhead sea turtles (Caretta caretta) dispersed widely from an aggregation near Port Canaveral, Florida, USA (28°23′N, −80°32′W) after breeding. Northbound males
migrated further (990 ± 303 km) than southbound males (577 ± 168 km) and transited more rapidly (median initial dive duration = 6
(IQR = 4–16) versus 19 (IQR = 10–31) min, respectively).. Migration occurred along a depth corridor (20–40 m) except where
constricted by a narrow continental shelf width. Males foraged in areas 27 ± 41 km2 day−1 at locations <1–80 km from shore for 100.1 ± 60.6 days, with variability in foraging patterns not explained by turtle size
or geography. Post-breeding dispersal patterns were similar to patterns reported for adult female loggerhead sea turtles in
this region and adult male loggerhead sea turtles elsewhere in the northern hemisphere; however, foraging ground distributions
were most similar to adult female loggerhead sea turtles in this region. 相似文献
14.
Reproduction and recruitment of scleractinian corals in a high-latitude coral community, Amakusa, southwestern Japan 总被引:1,自引:0,他引:1
Reproduction and recruitment in high-latitude coral populations in Japan have been little studied. A comprehensive study of the reproduction and early life history was conducted on nine common scleractinian coral species in Amakusa, southwestern Japan (32°N) from 2001 to 2003 including; (1) fecundity (the proportion of colonies with mature eggs), (2) timing and synchrony of spawning, (3) initial larval settlement pattern, (4) recruitment, (5) post-settlement mortality. The fecundity was high (76.7–100%) in six of seven species examined in 2002 and 2003. Annual spawning of the seven species occurred from mid July to August in 2001–2003, when seawater temperature was at the annual maximum. Spawning was highly synchronised among conspecific colonies and species in 2002 and 2003, with five species spawning five to nine nights after the full moon and another two spawning around the new moon. Temporal patterns of larval settlement of three spawning species during the first 10 days after spawning were similar to those of other spawning species from low latitudes. The number of scleractinian recruits on settlement plates, deployed from July to October (the major recruitment period at the study site), was low (2 recruits/m2) for the three consecutive years. Post-settlement mortality of 1–1.5 month old spat of five species ranged between 88 and 100% over 3–10 months in the field, similar to the values reported for both high and low latitude species (>94–99%). Among the key stages examined, the low recruitment rate may be the most important step in limiting successful reproduction and recruitment of these high-latitude scleractinian populations. The low recruitment rate may be attributable to (1) the reduced influx of larval supply from other coral populations, which are smaller and more isolated at high-latitudes and (2) the longer precompetent larval phase of broadcast-spawning corals which results in an increased chance of larvae being dispersed away from parent populations. 相似文献
15.
Anne Marie Power Karen McCrann David McGrath Ruth M. O’ Riordan Christina Simkanin Alan A. Myers 《Marine Biology》2011,158(10):2149-2160
This study examined how the species composition of an intertidal barnacle guild varied according to physical gradients in
the environment at small scales governed by microclimates, medium scales of wave exposure and large scales of latitude. Barnacle
distributions at small and medium scales were sampled in Ireland between 51°29′ and 52°44′N and 6°50′ and 10°08′W. Sampling
on European shores spanned ~18° latitude from 37°05′ to 55°16′N. Barnacle surveys mainly took place in 2003–2004. An index
of wave fetch was calculated along the wave exposure gradient using a digital coastline-based model that was supported by
a biological exposure scale. A ‘dryness’ index was defined according to mean monthly wind speed, fetch along the average wind
direction and mean monthly air or sea surface temperatures for 2 years (January 2001–December 2002) which is the period when
the most recent adults in the barnacle community would have settled and grown to adulthood. The proportion of the dry-loving
barnacle Chthamalus montagui Southward increased within the barnacle guild at all scales as the habitat became warmer and drier. Barnacle densities were
high in all habitats, mean densities ranged from a minimum of 4.16 cm−2 on moderately exposed shores to a maximum of 6.27 cm−2 in sunlit or south-facing microclimates. Percentage cover of barnacles across the gradient of latitudes was usually >70%.
The results suggest that the distribution and abundance of interacting barnacle species on European coasts is strongly controlled
by abiotic factors, most likely temperature and desiccation. 相似文献
16.
17.
In this study, juvenile colonies of massive Porites spp. (a combination of P. lutea and P. lobata) from the lagoon of Moorea (W 149°50′, S 17°30′) were damaged and exposed to contrasting conditions of temperature and flow
to evaluate how damage and abiotic conditions interact to affect growth, physiological performance, and recovery. The experiment
was conducted in April and May 2008 and consisted of two treatments in which corals were either undamaged (controls) or damaged
through gouging of tissue and skeleton in a discrete spot mimicking the effects of corallivorous fishes that utilize an excavating
feeding mode. The two groups of corals were incubated for 10 days in microcosms that crossed levels of temperature (26.7 and
29.6°C) and flow (6 and 21 cm s−1), and the response assessed as overall colony growth (change in weight), dark-adapted quantum yield of PSII (F
v/F
m), and healing of the gouged areas. The influence of damage on growth was affected by temperature, but not by flow. When averaged
across flow treatments, damage promoted growth by 25% at 26.7°C, but caused a 25% inhibition at 29.6°C. The damage also affected
F
v/F
m in a pattern that differed between flow speeds, with a 10% reduction at 6 cm s−1, but a 4% increase at 21 cm s−1. Regardless of damage, F
v/F
m at 21 cm s−1 was 11% lower at 26.7°C than at 29.6°C, but was unaffected by temperature at 6 cm s−1. The lesions declined in area at similar rates (4–5% day−1) under all conditions, although the tissue within them regained a normal appearance most rapidly at 26.7°C and 6 cm s−1. These findings show that the response of poritid corals to sub-lethal damage is dependent partly on abiotic conditions,
and they are consistent with the hypothesis that following damage, calcification and photosynthesis can compete for metabolites
necessary for repair, with the outcome affected by flow-mediated mass transfer. These results may shed light upon the ways
in which poritid corals respond to biting by certain corallivorous fishes. 相似文献
18.
Although mysids play important roles in marine food chains, studies on their production are scarce, especially for warm-water
species. We investigated life history and production of Orientomysis robusta in a shallow warm-temperate habitat of the Sea of Japan. Its spawning and recruitment occurred throughout the year; 19 overlapping
cohorts were recognizable over an annual cycle. The summer cohorts recruited in July–September exhibited rapid growth, early
maturity, small brood size, and small body size. A converse set of life history traits characterized the autumn–winter cohorts
recruited in October–March. The spring cohorts recruited in April–June had intermediate characteristics of both cohorts. Life
spans were 19–33, 21–48, and 69–138 days for summer, spring, and autumn–winter cohorts, respectively, and mortality rates
were high for spring and summer cohorts, especially during June–August but were low for autumn–winter cohorts. Production
calculated from the summation of growth increments was 488.8 mg DW m−2 year−1 with an annual P/B ratio of 21.26. The short life span seems to be responsible for such an extremely high P/B ratio. A method not requiring recognition and tracking cohorts gave similar values (534.0 mg DW m−2 year−1 and 20.49). The close agreement in production values between the two methods indicates our estimates are valid. 相似文献
19.
Bivalves are important in shallow marine habitats, not at least being the major food resource for seaducks such as the common
scoter (Melanitta nigra), thousands of which are wintering on the Western Coastal Banks, near the Belgian-French border (North Sea). Next to this
ecological importance, fishable stocks of one of these bivalves, Spisula subtruncata, occur in the area. This study aimed at investigating S. subtruncata’s spatial distribution, population dynamics and productivity and its implications for a sustainable Spisula fishery in seaduck wintering areas. The spatial distribution of S. subtruncata was studied in 1994 and 1997 in two areas of the Belgian Western Coastal Banks. The population dynamics and production were
investigated by monthly sampling of two stations between April 1995 and April 1996 and a seasonal sampling between April 1996
and April 1998. Spisula subtruncata had a patchy distribution in the deeper (6 m), fine sandy (200 ± 20 μm) sediments of the Abra alba community, mainly found in the western most part of the Western Coastal Banks. In August 1995, an overwhelming and successful
recruitment was observed in this area: local densities were as high as 150,000 ind m−2. Minor, non-successful recruitments were detected in August 1996 and 1997. Due to space limitation, high densities of S. subtruncata are hypothesized to be responsible for the occurrence of aberrant shapes as observed from August 1996 onwards. Growth was
described by a seasonally oscillating version of the von Bertalanffy growth function (VBGF): a growth stop was observed from
late autumn till early spring. The VBGF parameters K (growth constant) and L
∞ (asymptotic length) were estimated at 0.7–0.9 and 31–33 mm. A combination of length and individual biomass increment showed:
(1) a faster length increment of smaller individuals during the second growing period (catching-up phenomenon), (2) a constant
length combined with a decreasing individual biomass during the suboptimal winter periods (except for the first winter, when
the individual biomass slightly increased), (3) a positive relationship between the individual biomass decrease and the seawater
temperature during the winter periods, and (4) a strong increase of the individual biomass in early spring (April 1997 and
1998) because of gametogenesis, followed by a decrease because of spawning (August 1997). The extremely high total production
of the 1995 year class in the tidal gully (Potje) during the study period was estimated at approximately 1,500 g ash-free
dry weight (ADW) m−2 or 600 g ADW m−2 on average per year. Shellfisheries for S. subtruncata within seaduck wintering areas, such as the Western Coastal Banks, should be carefully deliberated since (1) an important
food resource for the seaducks will decrease, (2) the ecologically most diverse and rich macrobenthic A. alba community will be heavily affected, and (3) the recovery of Spisula populations after depletion is expected to be erratic. 相似文献
20.
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