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1.
A. L. Moran 《Marine Biology》1997,128(1):107-114
An understanding of spawning and larval development can be fundamental to interpreting the abundance, distribution, and population
structure of marine invertebrate taxa. Tegula funebralis (A. Adams, 1855), the black turban snail, has been the focus of numerous ecological studies on the Pacific coast of North
America. To date, there are only conflicting and anecdotal reports of spawning, and there is no information on larval or juvenile
development for this conspicuous and abundant species. On 19 September 1995, two individuals of T. funebralis were observed free-spawning gametes into seawater in tanks at the Oregon Institute of Marine Biology. Embryos and larvae
were subsequently reared to metamorphosis and beyond. Development was pelagic and similar to development described for other
trochids, and larvae were observed not to feed at any stage. Larvae began to metamorphose at 5.7 to 6.7 d and settled at 260
μm shell length. Juveniles grew ≃ 10 μm in shell length per day and appeared to feed on detritus. Juveniles lacked some adult
diagnostic shell characters, including two columellar nodes and a closed umbilicus. In the field, small (<3 mm) juveniles
occurred in the adult habitat on all sampling dates between October and March. Small juveniles were found only under rocks
and were most abundant under rocks partially buried in coarse sand, suggesting that juveniles may utilize a specific microhabitat
within the adult T. funebralis habitat.
Received: 7 October 1996 / Accepted: 17 October 1996 相似文献
2.
Michael P. Harris Francis Daunt Mark Newell Richard A. Phillips Sarah Wanless 《Marine Biology》2010,157(4):827-836
Most seabirds die outside the breeding season, but understanding the key factors involved is hampered by limited knowledge
of nonbreeding distributions. We used miniature geolocating loggers to examine the movements between breeding seasons of Atlantic
puffins Fratercula arctica from a major North Sea colony where numbers have declined in recent years, apparently due to increased overwinter mortality.
The most intensively used region was the northwestern North Sea but most puffins also made excursions into the east Atlantic
in the early winter. Ringing recoveries previously indicated that adults from British east coast colonies remained within
the North Sea and hence were spatially segregated from those breeding on the west throughout the year. Updated analyses of
ringing recoveries support results from geolocators suggesting that usage of Atlantic waters is a recent phenomenon. We propose
that the increased adult mortality is related to changes in distribution during the nonbreeding period and reflects worsening
conditions in the North Sea. 相似文献
3.
Seagrass beds are often considered to be important nurseries for coral reef fish, yet the effectiveness of these nursery functions
(refuge and food availability) at different juvenile stages is poorly understood. To understand how the demands of juvenile
fish on seagrass nursery functions determines the timing of ontogenetic habitat shifts from seagrass beds to coral reefs,
we conducted visual transect survey and field tethering and caging experiments on three different sizes of the coral reef
fish Pacific yellowtail emperor (Lethrinus atkinsoni) during its juvenile tenure in seagrass beds at Ishigaki Island, southern Japan. The study showed that although the number
of individual L. atkinsoni juveniles decreased by >90 % during their stay in the seagrass nursery, the shelter and/or food availability functions of
the nursery, at least for a juvenile size of approximately 5 cm total length (TL), provided the best survival and growth option.
The timing of ontogenetic migration to coral reefs of larger fish (>8 cm TL) was attributed to foraging efficiency for larger
food items in different habitats. Overall, the function of the seagrass bed nursery changed with juvenile body size, with
marginally higher survival and significantly greater growth rates during early juvenile stages in seagrass beds compared to
coral reefs. This would contribute to the enhancement in the number of individuals eventually recruited to adult populations. 相似文献
4.
Mitochondrial DNA and electronic tracking reveal population structure of Atlantic bluefin tuna (Thunnus thynnus) 总被引:1,自引:0,他引:1
Population subdivision was examined in Atlantic bluefin tuna (Thunnus thynnus) through sequencing of the control region of the mitochondrial genome. A total of 178 samples from the spawning grounds in
the Gulf of Mexico, Bahamas and Mediterranean Sea were analyzed. Among the samples from these locations were 36 electronically
tagged bluefin tuna that were tagged in the North Atlantic and subsequently traveled to one of these known spawning grounds
during the spawning season. Bluefin tuna populations from the Gulf of Mexico and the Mediterranean Sea were found to be genetically
distinct based on Φst, and sequence nearest neighbor analyses, showing that these two major spawning areas support independent stocks. Sequence
nearest neighbor analysis indicated significant population subdivision among the Gulf of Mexico, western Mediterranean and
eastern Mediterranean Sea. However, it was not possible to find significant pairwise differences between any sampling areas
when using all samples. If only samples that had a high likelihood of assignment to a specific spawning site were used (young
of the year, spawning adults), the differentiation increased among all sampling areas and the Western Mediterranean Sea was
distinct from the Eastern Mediterranean Sea and the Gulf of Mexico. It was not possible to distinguish samples from the Bahamas
from those collected at any of the other sampling sites. These data support tagging results that suggested distinctness of
the Gulf of Mexico, Eastern and Western Mediterranean Sea spawning areas. This level of stock differentiation is only possible
if Atlantic bluefin tuna show strong natal homing to individual spawning grounds. 相似文献
5.
The feeding ecology of the green tiger shrimp Penaeus semisulcatus was studied in inshore fishing grounds off Doha, Qatar, using a combination of stable isotope (δ13C and δ15N) analysis and gut contents examination. Samples of post-larvae, juvenile and adult shrimp and other organisms were collected from intertidal and subtidal zones during the spawning season (January–June). Shrimp collected from shallow water seagrass beds were mostly post-larvae and juveniles and were significantly smaller than the older juveniles and adults caught in deeper macroalgal beds. Gut content examination indicated that post-larvae and juvenile shrimp in seagrass beds fed mainly on benthos such as Foraminifera, polychaetes, benthic diatoms and small benthic crustaceans (amphipods, isopods and ostracoda), whereas larger shrimp in the macroalgal beds fed mainly on bivalve molluscs and to a lesser extent polychaetes. In shrimp from both seagrass and algal beds, unidentifiable detritus was also present in the gut (18, 32%). δ13C values for shrimp muscle tissue ranged from −9.5 ± 0.26 to −12.7 ± 0.05‰, and δ15N values increased with increasing shrimp size, ranging from 4.1 ± 0.03 to 7.7 ± 0.11‰. Both δ15N values and δ13C values for shrimp tissue were consistent with the dietary sources indicated by gut contents and the δ13C and δ15N values for primary producers and prey species. The combination of gut content and stable isotope data demonstrates that seagrass beds are important habitats for post-larvae and juvenile P. semisulcatus, while the transition to deeper water habitats in older shrimp involves a change in diet and source of carbon and nitrogen that is reflected in shrimp tissue stable isotope ratios. The results of the study confirm the linkage between sensitive shallow water habitats and the key life stages of an important commercially-exploited species and indicate the need for suitable assessment of the potential indirect impacts of coastal developments involving dredging and land reclamation. 相似文献
6.
Use of sibling relationship reconstruction to complement traditional monitoring in fisheries management and conservation of brown trout 下载免费PDF全文
Mikhail Ozerov Tauno Jürgenstein Tutku Aykanat Anti Vasemägi 《Conservation biology》2015,29(4):1164-1175
Declining trends in the abundance of many fish urgently call for more efficient and informative monitoring methods that would provide necessary demographic data for the evaluation of existing conservation, restoration, and management actions. We investigated how genetic sibship reconstruction from young‐of‐the‐year brown trout (Salmo trutta L.) juveniles provides valuable, complementary demographic information that allowed us to disentangle the effects of habitat quality and number of breeders on juvenile density. We studied restored (n = 15) and control (n = 15) spawning and nursery habitats in 16 brown trout rivers and streams over 2 consecutive years to evaluate the effectiveness of habitat restoration activities. Similar juvenile densities both in restored and control spawning and nursery grounds were observed. Similarly, no differences in the effective number of breeders, Nb(SA), were detected between habitats, indicating that brown trout readily used recently restored spawning grounds. Only a weak relationship between the Nb(SA) and juvenile density was observed, suggesting that multiple factors affect juvenile abundance. In some areas, very low estimates of Nb(SA) were found at sites with high juvenile density, indicating that a small number of breeders can produce a high number of progeny in favorable conditions. In other sites, high Nb(SA) estimates were associated with low juvenile density, suggesting low habitat quality or lack of suitable spawning substrate in relation to available breeders. Based on these results, we recommend the incorporation of genetic sibship reconstruction to ongoing and future fish evaluation and monitoring programs to gain novel insights into local demographic and evolutionary processes relevant for fisheries management, habitat restoration, and conservation. 相似文献
7.
Three congeneric species of fiddler crabs, Uca pugilator (Bosc, 1802), U. pugnax (Smith, 1870), and U. minax (LeConte, 1855), co-occur in estuaries along the east coast of North America, from Cape Cod to northern Florida. Although U. minax adults are generally found at lower salinities than the other two species, the distributions of all three species overlap to some degree. The distribution of megalopae and juvenile fiddler crabs (from first crab stage to those with a carapace width of 3.0 mm) was examined at four sites along a salinity gradient (from 35.0±2.0 to 3.0±3.0;
) in the North Inlet Estuary, South Carolina, USA, in August 2002. A PCR-RFLP technique was developed to identify individuals from the genus Uca to species from first zoea through the early crab stages. An examination of the distribution of early life stages showed that U. minax reinvades low-salinity adult habitats at settlement, following planktonic larval development in the coastal ocean. Also, juveniles of U. pugilator were found to occupy Spartina alterniflora stands, where adult conspecifics rarely occur. Species frequencies were different for adults compared to early life stages in low-salinity areas of the marsh, where populations overlap. Settlement and survival dynamics of early life-history stages in wet and dry years likely determine the distribution of adult Uca spp. populations along salinity gradients in estuarine ecosystems.Communicated by J.P. Grassle, New Brunswick 相似文献
8.
We examined site differences in the elemental composition of the primordium and ontogenetic variability of Sr in otoliths
of fish from Australia and New Zealand and, as an out-group, the North Atlantic. Differences among sites in primordium composition
are slight, but significant for all five elements assayed (Sr, Pb, Cu, Zn and Hg), but principally reflect differences between
the North Atlantic and SW Pacific specimens, do not replicate for independent samples in the SW Pacific and constitute a poor
“natural tag” in roughy, with <25% of fish successfully assigned to source location. However, mean Sr weight-fractions at
the primordium showed similar latitudinal variation across sites in Australia, New Zealand and the Tasman Sea, indicating
both spatially structured populations and a common structuring process across the region. Comparisons of ontogenetic variability
of Sr in otoliths from juveniles and young adults within and between sites in the SW Pacific strongly support the hypothesis
that variability in this element is site-specific and environmentally sensitive, although the environmental factors involved
are not obvious. The otolith analysis confirms previous suggestions that juvenile and adult Hoplostethus atlanticus are relatively sedentary, but also indicates that the population sub-structuring by age within sites is more complex and
there are likely to be more spawning areas in Australian waters than previously thought. More broadly, although single point
analysis of otolith composition at the primordium resolves a population structure in roughy, alone it is not precise enough
to test hypotheses about the processes causing this structure. Ontogenetic variability in Sr provides better resolution of
spatial structure, even in a relatively homogenous marine environment like the deep ocean, and also provides insight into
behavioural and ecological factors. Ontogenetic analyses of Sr in otoliths are expensive to obtain, require more effort in
specimen preparation than single point analyses, and are difficult to compare statistically, but the increased information
they yield warrants their broader consideration in marine species. 相似文献
9.
Detailed inventories of the benthos and field studies of the settlement and recruitment processes of marine benthic invertebrates
require accurate identification of newly settled larvae and early juvenile stages. We provide morphological criteria, visible
under a good quality dissecting stereomicroscope, by which to discriminate between species of the settling larval and early
postlarval stages (∼250 to 700 μm shell length) of mussels of the genus Mytilus on the west coast of Vancouver Island and Southern California. Compared to the bay mussel (M. trossulus), the sea mussel (M. californianus) has: (i) a shallower and flatter umbo, the latter corresponding to a significantly less pronounced prodissoconch I (PI)
curvature and (ii) a greater PI length; as well as (iii) a wider separation between the provincular lateral teeth (PLT). The
PLT distance is a new term denoting the separation between the midpoint of two reddish pigment spots of the provinculum (larval
hinge apparatus) region of settling larvae and early postlarvae of Mytilus spp. from the East Pacific Coast. These spots mark the larger provincular lateral teeth, situated at either end of the provinculum.
We confirmed the validity of morphological criteria by comparing PCR products of genomic DNA of provisionally identified postlarvae.
Furthermore, measurements of PI lengths and PLT distance from well-preserved postlarvae of sea mussels (M. californianus) and of bay mussels (M. galloprovincialis) from Southern California indicate that the PI morphology and morphometry, and PLT distance criterion apply for that region
as well. The criteria presented here can also apply to the advanced (competent) veliger stages, as the latter may settle (i.e.
become the “settling” stage) upon encountering a suitable substrate. Our present and previously published work provide economical
and effective identification methods that can be used to discriminate among early life history stages (∼250 μm to 5.0 mm shell
length) of Mytilus spp. along the west coast of North America.
Received: 10 November 1999 / Accepted: 6 September 2000 相似文献
10.
The aim of this study was to determine whether the composition of the demersal fish fauna in coastal marine waters in temperate
Australia changes markedly with increasing water depth and distance from the shore and whether the composition of the fish
fauna in water depths of 5 to 35 m undergoes cyclic, seasonal changes. Samples of demersal fishes were therefore collected
by trawling over the predominantly sandy substrate at nine sites located in water depths of 5 to 15 m or 20 to 35 m and within
20 km of the shore in four regions along ∼200 km on the lower west coast of Australia. The sampling regime involved trawling
for fishes at each site at night in seven consecutive seasons between the summer of 1990/1991 and winter of 1992. A total
of 72 435 fishes, representing 77 families, 143 genera and 172 species was caught. The compositions of the fish faunas in
offshore waters with depths of 5 to 35 m were shown to differ markedly from those previously recorded for nearshore marine
waters in the same regions. However, as some species, such as Sillago burrus, S. vittata, S. bassensis and Rhabdosargus sarba, increase in size, they move out from their nursery areas in nearshore waters into deeper and more offshore waters, where
spawning occurs. Ordination showed that, in each of the four regions, the composition of the fish fauna in depths of 5 to
15 m differs from that in depths of 20 to 35 m. This difference is attributable to the fact that some species, such as S. burrus, S. vittata and Upeneichthys lineatus, are far more abundant in depths of 5 to 15 m, whereas other species, such as S. robusta, U. stotti and Lepidotrigla modesta, occur predominantly in depths of 20 to 35 m. However, the samples collected from the single site that was inshore but in
deeper water demonstrate that the composition of the fish fauna is influenced by distance from shore as well as by water depth.
The compositions of the fish faunas differed with latitude, largely due to the fact that some subtropical species, such as
Polyspina piosae, S. burrus and S. robusta, did not extend down into the more southern regions. Ordination also showed that the composition of the fish faunas at all
but one of the nine sites underwent pronounced and consistent cyclic, seasonal changes. This seasonal cyclicity at the different
sites was attributable to sequential patterns of immigrations and emigrations by a number of fish species during the course
of the year. These seasonal migrations involved, inter alia (1) movements of certain species from their nursery areas into
these deeper waters, e.g. S. bassensis and Scobinichthys granulatus; (2) migrations into and off the sandy areas of the inner continental shelf, e.g. Arnoglossus muelleri; (3) migrations to spawning areas, e.g. Sillago robusta; and (4) movements into areas where detached macrophytes accumulate in winter, e.g. Cnidoglanis macrocephalus and Apogon rueppellii.
Received: 21 August 1998 / Accepted: 9 February 1999 相似文献
11.
To date, movement patterns of juvenile sand tigers (Carcharias taurus) along the east coast of the USA have been loosely defined. Given the magnitude of the purported decline in the sand tiger population in the western North Atlantic (WNA), characterization of the species’ movement patterns throughout this broad area is essential for the effective management and recovery of this population. Using passive acoustic telemetry, pop-up satellite archival transmitting tags, and conventional fishery-dependent tag/recapture data, seasonal movements of juvenile sand tigers (ages 0–2 years; <125 cm fork length) were monitored between Maine and Florida along the US east coast from 2007 to 2013. Collectively, tag data indicated that juvenile sand tigers undergo extensive seasonal coastal migrations moving between summer (June–October) habitat (Maine to Delaware Bay) and winter (December–April) habitat (Cape Hatteras to central Florida) during the spring (April–June) and fall/early winter (October–December). Juvenile sand tigers occurred in a wide range of temperatures (9.8–26.9 °C) throughout the year, but spent the majority of their time in water from 12 to 20 °C. Given the extensive movements and continuous utilization of relatively shallow (<80 m) nearshore waters exhibited by these relatively small individuals throughout their first years of life, it is imperative that precautions be taken to limit negative effects of anthropogenic interactions on this species (i.e., fisheries bycatch, coastal degradation) in an effort to rebuild and sustain the WNA population. 相似文献
12.
R. W. Brill B. A. Block C. H. Boggs K. A. Bigelow E. V. Freund D. J. Marcinek 《Marine Biology》1999,133(3):395-408
We measured the horizontal and vertical movements of five adult yellowfin tuna (Thunnus albacares, estimated body mass 64 to 93 kg) near the main Hawaiian Islands, while simultaneously gathering data on oceanographic conditions
and currents. Fish movements were recorded by means of ultrasonic depth-sensitive transmitters. Depth–temperature and depth–oxygen
profiles were measured with vertical conductivity–temperature–depth (CTD) casts, and the current-velocity field was surveyed
using an acoustic Doppler current profiler (ADCP). Large adult yellowfin tuna spent ≃60 to 80% of their time in or immediately
below the relatively uniform-temperature surface-layer (i.e. above 100 m), a behavior pattern similar to that previously reported
for juvenile yellowfin tuna, blue marlin (Makaira nigricans), and striped marlin (Tetrapturus audax) tracked in the same area. In all three species, maximum swimming depths appear to be limited by water temperatures 8 C°
colder than the surface-layer water temperature. Therefore, neither large body mass, nor the ability to maintain elevated
swimming-muscle temperatures due to the presence of vascular counter-current heat exchangers in tunas, appears to permit greater
vertical mobility or the ability to remain for extended periods below the thermocline. In those areas where the decrease in
oxygen with depth is not limiting, the vertical movements of yellowfin tuna, blue marlin and striped marlin all appear to
be restricted by the effects of water temperature on cardiac muscle function. Like juvenile yellowfin tuna, but unlike blue
marlin and striped marlin, adult yellowfin tuna remained within 18.5 km of the coast and became associated with floating objects,
including anchored fish-aggregating devices (FADs) and the tracking vessel. Like juvenile yellowfin tuna, large adult yellowfin
repeatedly re-visit the same FAD, and appear able to navigate precisely between FADs that are up to 18 km apart. The median
speed over ground ranged from 72 to 154 cm s−1. Neither speed nor direction was strongly influenced by currents.
Received: 27 March 1998 / Accepted: 13 November 1998 相似文献
13.
Summary This paper documents differences in seasonal time of river ascent and descent, and instream behavior of adult wild and sea-ranched Atlantic salmon (Salmo salar) of the Norwegian River Imsa stock during the period 1981–1989. Wild fish use River Imsa as a nursery, and at an age of 2 years most of them migrate to the sea as smolts. The sea ranched fish are hatchery reared offspring of the River Imsa stock and are released as smolts at the mouth of the river. They are thus deprived of juvenile river life and a downstream smolt migration. Wild and sea ranched salmon feed for 1 or more years in the Norwegian Sea before homing as spawners. Both groups returned simultaneously to coastal Norway, but sea ranched fish ascended the river later and descended sooner after spawning than wild fish. All wild females and almost all wild males (96.2%) spawned in the river, whereas 13.5% and 36.7%, respectively, of the mature sea-ranched females and males left the river unspawned. The annual number, but not the proportion, of unspawned fish increased with increasing density of adult salmon in the river. Unspawned females were medium sized and small (45–70 cm); unspawned males were medium sized and large (50–90 cm). Independent of the density of spawners in the river, sea ranched fish moved up- and downstream the river more often than wild fish. More than 20% of the sea-ranched salmon and less than 1% of the wild salmon passed a trap 100 m above the river outlet more than once in each direction during the same spawning reason. Moreover, sea-ranched salmon were about twice as often seriously injured during spawning as wild fish. Lack of juvenile experience from the river may be the main reason for the behavioral differences between sea-ranched and wild fish.
Offprint requests to: B. Jonsson 相似文献
14.
Growth and reproduction were compared among six geographically and genetically distinct intertidal populations of the annual,
semelparous, dorid nudibranch Adalaria proxima (Alder & Hancock) to evaluate variation in fitness-related traits. The six populations spanned the geographic range in the
northern British Isles: NE England (Cowling Scar), E Scotland (Kinkell Braes), NW Scotland (Loch Eriboll), W Scotland (Cuan
Ferry), Northern Ireland (Portaferry), and N Wales (Menai Bridge). Nudibranchs from five sites were collected in July to August
1992 as post-metamorphic juveniles and were laboratory-reared under the same conditions of ambient temperature and photoperiod
for up to 10 months and the completion of spawning. Individuals from the sixth site were added to the experiment in December
1992. Growth was monitored every 2 weeks, and reproductive performance was expressed as a weight-adjusted dimensionless index
(ΣRI) of each individual's spawnings summed over the reproductive period. In general, larger nudibranchs produced larger first
spawn masses and more total spawn than did smaller nudibranchs, but these size-related trends were observed only in some populations.
The patterns of energy partitioning to spawnings varied significantly among populations, from allocations of a large number
of eggs to few spawn masses (Loch Eriboll) to production of many small spawnings over a long spawning period (Portaferry).
There was no relationship between maximum body size and the amount of spawn produced after the first spawning, nor to the
length of the spawning period or the number of spawn produced. Both Menai Bridge and Kinkell Braes had low mean population
ΣRI, reflecting a very poor reproductive performance, given their large maximum (pre-spawning) body sizes. By contrast, the Loch
Eriboll, Cuan Ferry, and Portaferry populations all displayed high mean population ΣRI, albeit as a result of differing combinations of numbers and sizes of spawn masses and duration of the spawning period. This
high variance of reproductive allocation among populations, and previous evidence of relatively stable among-population differences
in allozyme frequencies, adult color, and embryo characteristics suggest very restricted larval transport of lecithotrophic
larvae of A. proxima.
Received: 10 December 1998 / Accepted: 23 March 2000 相似文献
15.
The reproductive biology of female Penaeus japonicus Bate was investigated in the Ariake Sea and Tachibana Bay (located outside the Ariake Sea), Japan from 1994 to 1996. Interannual,
seasonal, individual female body size and spatial influences on the incidence of spawning were examined. The proportion of
inseminated females, increased with increasing body size up to 170 mm body length (BL) and decreased thereafter. The minimum
size at maturity was similar between years; 130 to 140 mm BL. The minimum size of individuals with developing ovaries or spermatophores
differed from that of ripe females by 20 to 25 mm. Spawning occurred in the central part of the Ariake Sea and Tachibana Bay
but rarely in the inner part. P. japonicus had a clear reproductive cycle. Spawning started earlier and ended later, occurring from mid-May to mid-October, in the eastern
central part of and outside of the Ariake Sea compared with the western central part, where spawning occurred from mid-June
to mid-September. Spawning dynamics differed across seasons, body sizes and areas but not across years. The seasonal peak
in the proportion of ripe females varied with body size. In small individuals (130 to 169 mm BL), no peak was observed, whereas
in large individuals (>170 mm BL) the proportion of ripe individuals peaked in June. The proportion of ripe individuals increased
with increasing body size and was high outside the Ariake Sea. Factors causing the variation in spawning dynamics are discussed.
Received: 30 November 1998 / Accepted: 12 October 1999 相似文献
16.
Lingcod, Ophiodon elongatus Girard, have a 3-month pelagic larval stage and are an important recreational and commercial species on the west coast of
North America. Cytochrome-c oxidase I sequences from tissue samples were used to characterize population structure and infer
patterns of gene flow from California to Alaska. No significant genetic structure was found when estimates of Wright’s F
ST (i.e., ΦST) were generated among all populations sampled. Nesting populations within regions, however, indicated that the inner coast
of Washington State is distinct, a result corroborating previous allozyme work. Coalescent-based estimates of gene flow indicate
that although migration can be high from an evolutionary perspective, nearly half of all comparisons among populations showed
no gene flow in at least one direction. From an ecological perspective, moderate migration rates (Nm < 10) among most populations provide surprisingly limited connectivity at large (∼ 1,000 km) and small (∼100 km) spatial
scales. Coalescent-based estimates also show that gene flow between the inner and the outer coasts is asymmetric, a result
consistent with prevailing surface currents. Because the expected inter-locus variances for coalescent-based estimates of
gene flow are likely large, future work will benefit from analyses of nuclear DNA markers. However, limited demographic connectivity
on large spatial scales may help explain why stock recovery has been uneven, with greater recovery in the northern (87% rebuilt)
than in the southern (24% rebuilt) fishery region, supporting a regional management strategy. These results suggest that despite
a 3-month pelagic larval stage, some areas may be effectively closed with respect to both population dynamics and fishery
management issues. 相似文献
17.
Juvenile gray snapper, Lutjanus griseus, are believed to use bays and estuaries in southern Florida as nurseries before moving out to the adjoining reef tract as
adults. Using high-resolution sector field-inductively coupled plasma-mass spectrometry (SF-ICP-MS), the elemental chemistry
of the otoliths of juveniles from five nursery regions was resolved by establishing elemental “signatures” for each region.
In this study we simultaneously analyzed 32 elements including a suite of rare earth elements. A stepwise variable selection
procedure retained a subset of eight elements that contributed substantially to separating otolith samples, including two
rare earth elements; this is one of the first studies in which rare earth elements in otoliths have contributed to separation
of fish stocks. The classification success rate in assigning fishes to the correct region of origin was 82%. Resolution of
sites less than 10 km apart suggested high site fidelity in juvenile gray snapper and little mixing of water masses between
sites. The juvenile nursery signatures will be used to determine the relative contribution of different nurseries to the adult
population on an adjoining reef tract. 相似文献
18.
Paolo Casale Marco Affronte Dino Scaravelli Bojan Lazar Carola Vallini Paolo Luschi 《Marine Biology》2012,159(7):1527-1535
Knowledge about migratory routes and highly frequented areas is a priority for sea turtle conservation, but the movement patterns of juveniles frequenting the Adriatic have not been investigated yet, although juveniles represent the bulk of populations. We tracked by satellite six juvenile and one adult female loggerhead from the north Adriatic. The results indicated that loggerhead juveniles (1) can either show a residential behaviour remaining in the Adriatic throughout the year or perform seasonal migrations to other areas, (2) can remain even in the coldest, northernmost area during winter, (3) can frequent relatively small foraging areas, (4) mostly frequent the eastern part of the Adriatic, and (5) follow preferred migratory routes along the western and eastern Adriatic coasts. The movements of the adult turtle also revealed (6) a behavioural polymorphism in Mediterranean adults, which included a lack of area fidelity and connection between distant neritic foraging grounds. 相似文献
19.
Otolith chemistry can be used to assess pelagic larval fish connectivity by comparing spatially variable otolith edge chemistry (corresponding to the site of collection) to otolith core chemistry (corresponding to the site of hatching). However, because the otolith’s edge and core represent different life stages, the deposition of elements may differ, thus complicating direct comparisons of edge and core chemistry to investigate connectivity. Here we present data from a field experiment in which otoliths from embryos (3 days post-fertilization) and juveniles of Stegastes partitus were collected at the same site and time, and chemically analyzed to assess whether elemental concentrations of otoliths vary ontogenetically. Separate multivariate analyses, each investigating the spatial/temporal variability in the chemistry of either embryo otoliths or the edges of juvenile otoliths, revealed significant differences, suggesting an environmental influence to the chemical signals of otoliths. A nested multivariate analysis assessing whether otolith chemistry varied with life history stage (i.e., ontogenetic variability) indicated that elemental concentrations of embryo otoliths were significantly greater than that of juvenile otolith edges. Specifically, embryo elemental concentrations of Mn, Zn, Sn, Ba, Ce, and Pb were between 2 and 163 times greater than those of the corresponding juvenile otoliths, and thus the environment was not the primary determinant of embryo otolith chemistry. Consequently, caution is warranted when interpreting environmental patterns of otolith cores, particularly when using them as a proxy for natal signatures. 相似文献
20.
The annual occurrence of hypoxia (<25% oxygen saturation) in the bottom waters along the Swedish west coast coincides with
the postlarval settlement of Norway lobster, Nephrops norvegicus (L.). This study investigates behaviour and the experimental effects of low oxygen concentrations in juvenile N. norvegicus of different ages. All experimental individuals were reared to the juvenile (postlarval) stage in the laboratory and then
given sediment as a substratum. Behavioural responses to low oxygen concentrations were tested in early and late Postlarvae
1 exposed to normoxia (>80% oxygen saturation, pO2 > 16.7 kPa), moderate hypoxia (30% oxygen saturation, pO2 = 6.3 kPa) and hypoxia (25% oxygen saturation, pO2 = 5.2 kPa). The experiments were run for a maximum period of 24 h or until individuals died. Behaviour was studied using
sequential video recordings of four behavioural activities: digging, walking, inactivity or flight (escape swimming up into
the water column). Behaviour and mortality changed with lowered oxygen concentrations; energetically costly activities (such
as walking) were reduced, and activity in general declined. In normoxia, juveniles initially walked and then burrowed, but
when exposed to hypoxia they were mainly inactive with occasional outbursts of escape swimming. To increase oxygen availability
the juveniles were observed to raise their bodies on stilted legs (similar to adults in hypoxic conditions), but oxygen saturations
of 25% were lethal within 24 h. The results suggest that the main gas exchanges of early postlarval stages occur over the
general body surface. Burrowing behaviour was tested in Postlarvae 1 and 2 of different ages held in >80% oxygen saturation
for 1 wk. The difference in time taken to complete a V-shaped depression or a U-shaped burrow was measured. The results showed
a strong negative relationship between postlarval age and burrowing time, but all individuals made a burrow. Juveniles were
more sensitive to hypoxia than adults. Thus, the possible consequences of episodic hypoxia for the recruitment of Nephrops norvegicus and for the recolonization of severely affected areas are discussed.
Received: 4 August 1996 / Accepted: 11 October 1996 相似文献