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Peter B. Adams Churchill Grimes Joseph E. Hightower Steven T. Lindley Mary L. Moser Michael J. Parsley 《Environmental Biology of Fishes》2007,79(3-4):339-356
North American green sturgeon, Acipenser medirostris, was petitioned for listing under the Endangered Species Act (ESA). The two questions that need to be answered when considering an ESA listing are; (1) Is the entity a species under the ESA and if so (2) is the “species” in danger of extinction or likely to become an endangered species in the foreseeable future throughout all or a significant portion of its range? Green sturgeon genetic analyses showed strong differentiation between northern and southern populations, and therefore, the species was divided into Northern and Southern Distinct Population Segments (DPSs). The Northern DPS includes populations in the Rogue, Klamath-Trinity, and Eel rivers, while the Southern DPS only includes a single population in the Sacramento River. The principal risk factors for green sturgeon include loss of spawning habitat, harvest, and entrainment. The Northern DPS is not considered to be in danger of extinction or likely to become an endangered species in the foreseeable future. The loss of spawning habitat is not large enough to threaten this DPS, although the Eel River has been severely impacted by sedimentation due to poor land use practices and floods. The two main spawning populations in the Rogue and Klamath-Trinity rivers occupy separate basins reducing the potential for loss of the DPS through catastrophic events. Harvest has been substantially reduced and green sturgeon in this DPS do not face substantial entrainment loss. However there are significant concerns due to lack of information, flow and temperature issues, and habitat degradation. The Southern DPS is considered likely to become an endangered species in the foreseeable future. Green sturgeon in this DPS are concentrated into one spawning area outside of their natural habitat in the Sacramento River, making them vulnerable to catastrophic extinction. Green sturgeon spawning areas have been lost from the area above Shasta Dam on the Sacramento River and Oroville Dam on the Feather River. Entrainment of individuals into water diversion projects is an additional source of risk, and the large decline in numbers of green sturgeon entrained since 1986 causes additional concern. 相似文献
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The primary objective of this study was to determine the reproductive structure of the adult green sturgeon population in
the Rogue River. Green sturgeon were captured by gillnet in the lower 11.6–68.4 river kilometers in April to July 2000–2003
and September and October 2002–2003. Gonadal tissue, collected by biopsy, was processed histologically, blood was collected
from the caudal vasculature, and fork length (FL) and total length (TL) (±0.5 cm) were measured for each individual. Sex steroids,
testosterone (T), 11-ketotestosterone (11-KT), and estradiol-17β (E2), were measured by radioimmunoassay. Biological samples
were collected from a total of 88 green sturgeon of which 37 females and 41 males were confirmed by histological analysis.
Four gravid females, captured in the spring, were visually identified, and oocyte polarization index and ovarian follicle
diameter indicated that these females were in spawning condition. Gonadal samples collected from six individuals did not contain
gonial cells, hence the sex and stage of maturity in these individuals remains unknown. Of the 20 females captured in the
spring, 1 was vitellogenic, 4 were post-vitellogenic, and 15 were post-ovulatory. Twenty-one females were captured in the
fall of which 6 were pre-vitellogenic, 7 vitellogenic, and 8 post-ovulatory. Of the 16 males captured in the spring, 2 were
pre-meiotic, 8 were ripe or actively spermiating, and 6 were post-spermiation. Twenty-five males were captured in the fall:
11 pre-meiotic males and 14 post-spermiation. The majority of green sturgeon captured in the Rogue River were reproductively
active or had recently spawned indicating the importance of this river for the preservation of green sturgeon. 相似文献
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We reared shortnose and Atlantic sturgeons at different temperatures after hatch and measured yolk utilization rate and efficiency
(YUE), maximum standard length, survival and development of escape response. Newly hatched Atlantic sturgeon, were smaller
in size, more efficient at utilizing yolk (incorporating yolk to body tissue) and reached developmental stages sooner than
shortnose sturgeon reared at the same temperatures (13–15°C). Within each species, decreasing temperature delayed yolk absorption,
escape initiation, time to reach maximum size, and time to 100% mortality. However, YUEs and the size of the larvae at these
'stages' were independent of rearing temperature for both species. These results suggest that even as temperature drives metabolic
processes to speed up development, these two species are still extremely efficient at transferring yolk energy to body tissues.
The lower efficiencies experienced by larval shortnose may reflect difference in yolk quality between the two species and/or
the Atlantic sturgeon's higher conversion efficiency. The ability of these two sturgeon species to develop successfully and
efficiently under a wide range in temperatures may provide a competitive advantage over more stenothermic species and explain
their persistence through evolutionary time. 相似文献
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Ryan L. Benson Scott Turo Barry W. McCovey Jr. 《Environmental Biology of Fishes》2007,79(3-4):269-279
Green sturgeon, Acipenser medirostris, movement and migration within the Klamath and Trinity rivers were assessed using radio and sonic telemetry. Sexually mature
green sturgeon were captured with gillnets in the spring, as adults migrated upstream to spawn. In total, 49 green sturgeon
were tagged with radio and/or sonic telemetry tags and tracked manually or with receiver arrays from 2002 to 2004. Tagged
individuals exhibited four movement patterns: upstream spawning migration, spring outmigration to the ocean, or summer holding,
and outmigration after summer holding. Spawning migrations occurred from April to June, as adults moved from the ocean upstream
to spawning sites. Approximately 18% of adults, those not out mignation in the spring, made spring post-spawning outmigrations.
The majority of adults, those not outmigrating in the spring, remained in discrete locations characterized as deep, low velocity
pools for extended periods during the summer and early fall. Fall outmigration occurred when fish left summer holding locations,
traveled rapidly downstream, and exited the river system. High river discharge due to the onset of winter rainstorms and freshets
appear to be the key environmental cue instigating the fall outmigration. 相似文献
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The Rogue River, Oregon represents one of three important spawning systems for green sturgeon, Acipenser medirostris, in North America. In this paper we describe the spawning migration, spawning periodicity, and size at maturity for green
sturgeon caught in the Rogue River during 2000–2004. Green sturgeon were caught by gill net or angling; 103 individuals were
tagged with radio or sonic transmitters (externally or internally). Green sturgeon caught by gill net and angling ranged from
145 cm to 225 cm total length. Histological and visual examinations of gonad tissues indicated that most green sturgeon were
spawning or post-spawning adults that entered the Rogue River to spawn. Ripe individuals were caught when water temperature
was 10–18°C. Specimens carrying transmitters migrated 17–105 km up river; reaches consisting of likely spawning sites were
identified based on sturgeon migratory behavior. Most green sturgeon remained in the Rogue River until late fall or early
winter when flows increased, after which they returned to the ocean. Eight green sturgeon (males and females) returned to
the Rogue River 2–4 years after leaving, entering the river during March, April, and May when water temperatures ranged from
9°C to 16°C. None of the 103-tagged individuals entered the Rogue River during successive years. There appear to be few known
natural threats to adult green sturgeon in the Rogue River. However, our data suggest that a high percentage of adults that
spawn in the Rogue River (particularly males) were susceptible to harvest by commercial, Tribal, and sport fisheries after
leaving the system because they were not adequately protected by maximum size limits during the period of this study. The
implications of maximum size limits (or lack of size limits) to green sturgeon are discussed, and recent actions taken by
Oregon and Washington Fish and Wildlife Commissions to manage green sturgeon more conservatively are presented. 相似文献
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Synopsis We conducted laboratory trials to test the vulnerability of young white sturgeon, Acipenser transmontanus, to predation when an alternative prey was available. In trials with two species of predators, we observed two feeding patterns.
When equal numbers of white sturgeon and goldfish, Carassius auratus, were available, prickly sculpins, Cottus asper, ingested more white sturgeon. Conversely, northern pikeminnow, Ptychocheilus oregonensis, ate more juvenile coho salmon, Oncorhynchus kisutch, than white sturgeon in three out of four sets of trials, but ate more white sturgeon in one set of trials. White sturgeon
size and the availability of cover did not affect the proportions of prey species ingested. Our results indicate that predation
may be affecting survival of white sturgeon larvae and juveniles in the wild and could be one factor limiting recruitment
of young-of-the-year white sturgeon in some locations. 相似文献
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Khalil Eslamloo Bahram Falahatkar 《Journal of applied animal welfare science : JAAWS》2014,17(1):29-42
This study was carried out to investigate the effect of an acute stressor on the variation of some physiological and immunological parameters of Siberian sturgeon (Acipenser baerii) juveniles. Fish, reared in 3 tanks for 10 weeks, were used for this study. The acute stress of fish consisted of 2 min of air exposure stress. Plasma levels of cortisol, glucose, and lactate as well as lysozyme activity in plasma were measured before stress and 1 hr, 3 hr, 6 hr, 9 hr, 12 hr, and 24 hr after stress. The plasma cortisol significantly increased in the highest level 1 hr after stress, yet it gradually declined after 3 hr. The glucose significantly increased only 1 hr after stress. There was no significant difference between plasma lactate prestress and poststress. Moreover, lysozyme activity was enhanced by stress, thus reaching the highest level 9 hr after stress. The results of this study indicate that Siberian sturgeon not only have a rapid response to acute stress, but also a great capacity for recovery from stress, thus returning physiological parameters to prestress levels after 6 hr. 相似文献
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Jon C. Svendsen Janet Genz W. Gary Anderson Jennifer A. Stol Douglas A. Watkinson Eva C. Enders 《PloS one》2014,9(4)
Animal metabolic rate is variable and may be affected by endogenous and exogenous factors, but such relationships remain poorly understood in many primitive fishes, including members of the family Acipenseridae (sturgeons). Using juvenile lake sturgeon (Acipenser fulvescens), the objective of this study was to test four hypotheses: 1) A. fulvescens exhibits a circadian rhythm influencing metabolic rate and behaviour; 2) A. fulvescens has the capacity to regulate metabolic rate when exposed to environmental hypoxia; 3) measurements of forced maximum metabolic rate (MMRF) are repeatable in individual fish; and 4) MMRF correlates positively with spontaneous maximum metabolic rate (MMRS). Metabolic rates were measured using intermittent flow respirometry, and a standard chase protocol was employed to elicit MMRF. Trials lasting 24 h were used to measure standard metabolic rate (SMR) and MMRS. Repeatability and correlations between MMRF and MMRS were analyzed using residual body mass corrected values. Results revealed that A. fulvescens exhibit a circadian rhythm in metabolic rate, with metabolism peaking at dawn. SMR was unaffected by hypoxia (30% air saturation (O2sat)), demonstrating oxygen regulation. In contrast, MMRF was affected by hypoxia and decreased across the range from 100% O2sat to 70% O2sat. MMRF was repeatable in individual fish, and MMRF correlated positively with MMRS, but the relationships between MMRF and MMRS were only revealed in fish exposed to hypoxia or 24 h constant light (i.e. environmental stressor). Our study provides evidence that the physiology of A. fulvescens is influenced by a circadian rhythm and suggests that A. fulvescens is an oxygen regulator, like most teleost fish. Finally, metabolic repeatability and positive correlations between MMRF and MMRS support the conjecture that MMRF represents a measure of organism performance that could be a target of natural selection. 相似文献
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Use of non‐island,shallow nearshore beach environments by Gulf Sturgeon (Acipenser oxyrinchus desotoi) within the Mississippi Sound,USA 下载免费PDF全文
M. S. Peterson W. T. Slack P. O. Grammer J.‐M. Havrylkoff 《Zeitschrift fur angewandte Ichthyologie》2018,34(1):3-11
Large sub‐adult/adult western population Gulf Sturgeon move to barrier islands in winter to feed whereas eastern fish move offshore or to nearshore non‐island environments; most small sub‐adults/juveniles remain in the estuarine system during winter. To test this, we used an acoustic data set deployed around the Port of Gulfport (hereafter Port footprint, east gate, west gate) within Mississippi Sound. We documented between three and six fish on each receiver totaling 12,285 detections for all 19 receivers between September 2012–May 2013. Only 30% of fish had both a high number of overall detections and a high number of detection days. In contrast, from October 2013–May 2014, between three and nine fish were detected on each receiver but with only 2,371 detections. Five fish (29.4%) had a high number of detections but a reduced number of detection days in the acoustic array; all fish appeared to be transients. Adults, unexpectedly, had the most prevalent occurrence and number of detection days in these shallow, non‐island beach environments contrary to our initial hypothesis. Our data suggests annually variable, regional‐scale use of beach environments not associated with barrier islands that likely serve as a travel corridor between drainages/offshore barrier islands, or as feeding zones; these movements may enhance the potential for mortality in Mississippi Sound. 相似文献