Movement of radio-tagged anadromous sea lamprey during the spawning migration in the River Mondego (Portugal)

The available spawning habitat for the anadromous sea lamprey, Petromyzon marinus L., population that enters the River Mondego has been drastically reduced in the last 20 years. The installation of a fish passage in the first impassable dam, the Açude-Ponte, would enable sea lamprey to recolonise the 34.6-km river stretch between the Açude-Ponte and Raiva dams. In order to assess the suitability of the upstream river stretches for this species, 10 radio-tagged sea lamprey were released upstream of the Açude-Ponte dam and tracked continuously throughout the entire migratory path. Lamprey were unable to pass over intact weirs that had been built for recreational purposes. Sea lamprey movements were more frequent during dusk and night than other periods. Increased river discharge at night, resulting from the operation of the Raiva power station, stimulated lamprey movements but reduced ground speeds recorded. After reaching a certain location, some of the animals maintained their position for several weeks, before undergoing a new movement. Two of the main tributaries of this river stretch were used by some sea lamprey, indicating that the animals were able to find these historical spawning grounds.     

Foraging activity patterns in the goosander (Mergus merganser) and the red-breasted merganser (M. serrator) in relation to patterns of activity in their major prey species

Summary Diel and seasonal foraging activity patterns of goosanders (Mergus merganser L.) and red-breasted mergansers (M. serrator L.) were studied during the breeding season on the Rickleå River in northern Sweden (64°05N). In addition, the locomotor activity patterns of their most important prey species, the river lamprey (Lampetra fluviatilis (L.)) and the three-spined stickleback (Gasterosteus aculeatus L.), were recorded.During spring, as mergansers arrived in the breeding area, both species exhibited a bimodal, diurnal pattern of activity with morning and evening peaks. By June (the spawning period for the river lamprey and the migratory period for the three-spined stickleback), goosander activity had shifted to late in the evening. This new activity peak correlated well with the main activity period in the river lamprey. Red-breasted mergansers remained predominantly diurnal throughout the observation period. Their diurnal activity correlated with the activity of their major prey, the three-spined stickleback.Both merganser species utilize a specialized foraging technique, i.e. probing the river-bottom with the bill, to catch hiding fish more or less at random. This behaviour probably helps them to forage during the relatively bright summer nights and thus prey upon the abundant nocturnal river lamprey. The goosander preys upon the river lamprey to a greater extent than does the red-breasted merganser, thus leading to a temporal segregation in food resource utilization between the two duck species.     

Variability in migration timing of adult Pacific lamprey (<Emphasis Type="Italic">Lampetra tridentata</Emphasis>) in the Columbia River,U.S.A.

We examined the effects of river environment on the timing of spawning migrations by anadromous Pacific lamprey, Lampetra tridentata, in the Columbia River (U.S.A.). In a 41-year time series of adult lamprey counts, migration timing was earliest in warm, low-discharge years and latest in cold, high-flow years. Threshold temperatures associated with run timing were similar throughout the dataset despite significant impoundment-related warming, suggesting that temperature-dependent migration cues have been temporally stable. Within each year, migration rates of PIT-tagged lampreys were positively correlated with temperature and negatively correlated with discharge through multiple river reaches, offering additional evidence for environmental control of upstream movement. Both visual count and PIT-tag data indicated that there may be population-based differences in migration timing within the aggregate Columbia River lamprey run. These life history and behavioral results have potentially far-reaching implications for management of lamprey species.     

Potential changes to the biology and challenges to the management of invasive sea lamprey Petromyzon marinus in the Laurentian Great Lakes due to climate change

Control programs are implemented to mitigate the damage caused by invasive species worldwide. In the highly invaded Great Lakes, the climate is expected to become warmer with more extreme weather and variable precipitation, resulting in shorter iced‐over periods and variable tributary flows as well as changes to pH and river hydrology and hydrogeomorphology. We review how climate change influences physiology, behavior, and demography of a damaging invasive species, sea lamprey (Petromyzon marinus), in the Great Lakes, and the consequences for sea lamprey control efforts. Sea lamprey control relies on surveys to monitor abundance of larval sea lamprey in Great Lakes tributaries. The abundance of parasitic, juvenile sea lampreys in the lakes is calculated by surveying wounding rates on lake trout (Salvelinus namaycush), and trap surveys are used to enumerate adult spawning runs. Chemical control using lampricides (i.e., lamprey pesticides) to target larval sea lamprey and barriers to prevent adult lamprey from reaching spawning grounds are the most important tools used for sea lamprey population control. We describe how climate change could affect larval survival in rivers, growth and maturation in lakes, phenology and the spawning migration as adults return to rivers, and the overall abundance and distribution of sea lamprey in the Great Lakes. Our review suggests that Great Lakes sea lamprey may benefit from climate change with longer growing seasons, more rapid growth, and greater access to spawning habitat, but uncertainties remain about the future availability and suitability of larval habitats. Consideration of the biology of invasive species and adaptation of the timing, intensity, and frequency of control efforts is critical to the management of biological invasions in a changing world, such as sea lamprey in the Great Lakes.     

Reproductive ecology of the river lamprey

The reproductive ecology of river lamprey Lampetra fluviatilis was investigated during the spawning period 2003 in the River Derwent, north‐east England. Over this period 1199 ± 104 individuals day⁻¹(mean ±  s . d .) were counted on one spawning site (area c . 450 m²), but mark‐recapture estimates suggested that >5000 river lamprey used this site over the same period and egg deposition was estimated as 168 000 eggs m⁻². The operational sex ratio of river lamprey in spawning clusters changed between spawning phases, from domination by females during the nest‐building phase (male : female ratio, 1 : 3·46), to a preponderance of males during the spawning phase (male : female, 1 : 0·37), followed by a return to a majority of females after spawning (male : female, 1 : 3·74). Recapture data showed that >97% of recaptured, tagged males were recorded at two or more nests, whereas almost 50% of recaptured, tagged females were recorded at the same nest, suggesting a promiscuous mating system, with a tendency towards polygyny within the population. Within the lower 80 km of the River Derwent and its tributaries, evidence of river lamprey spawning was found at only six sites, and most spawning (>80% of the observed spawning population) was at one site.     

Availability of and access to critical habitats in regulated rivers: effects of low-head barriers on threatened lampreys

1.  Conservation of freshwater animal populations requires their access to, as well as sufficient availability of, critical habitats, such as those for reproduction. Abundant small-scale barriers may cause extensive fragmentation of freshwater habitat but, by comparison to larger structures their effects are rarely considered by catchment managers. The relationship between the distribution of, and access to, spawning habitat in a regulated river, characterized by abundant small barriers, was examined for river lamprey Lampetra fluviatilis , a threatened migratory fish.
2.  Telemetry of adult lamprey in the River Derwent, North East England was used to quantify upriver migration and access to spawning habitat, together with surveys of spawning habitat availability and spawning activity between 2002 and 2007.
3.  Access in to the Derwent appeared severely restricted by a tidal barrage, beyond which lamprey migrated rapidly in unobstructed reaches. Of all lamprey tagged in the lower 4 km of river, or ascending the barrage, 64% and 17% passed the first and second weirs respectively, with high flows crucial for this. Although over 98% of lamprey spawning habitat occurred more than 51 km upstream, on average just 1.8% of river lamprey spawners were recorded there.
4.  In order to protect or rehabilitate species or species assemblages, greater attention needs to be paid to the relative spatial distribution of low-head barriers and the resultant availability of key habitats within individual catchments. This is particularly important given the renewed emphasis internationally on low-head hydropower solutions as a source of renewable energy, and the rapid growth in numbers of low-head barriers in many catchments.     

Pre-spawning migration of adult Pacific lamprey, <Emphasis Type="BoldItalic">Entosphenus tridentatus</Emphasis>, in the Willamette River,Oregon, U.S.A.

We describe the migration distances and timing of the adult Pacific lamprey, Entosphenus tridentatus, in the Willamette River Basin (Oregon, U.S.A.). We conducted aerial surveys to track radio-tagged fish upstream of a major waterfall and hydropower complex en route to spawning areas. We detected 24 out of the 43 fish that passed the waterfall-hydropower complex. Of the detected fish, 17 were detected multiple times. Their maximum migration distance upstream in the mainstem Willamette approximated a normal distribution. The maximum distance migrated upstream did not significantly correlate with total body length (r = −0.186, P = 0.385) or date that the fish passed Willamette Falls (r = −0.118, P = 0.582). Fish migrated primarily during the spring to early summer period before stopping during the summer, when peak river temperatures (≥20°C). However, at least three fish continued to migrate upstream after September. Behavior ranged from relatively slow migration, followed by holding; to rapid migration, followed by slow migration further up in the basin. This study provides a basis for informing more detailed research on Pacific lamprey in the future.     

Time-related predator/prey interactions between birds and fish in a northern Swedish river

Summary Seasonal and diel activity patterns of mergansers, gulls, and terns along a river in northern Sweden were documented, as were those of their fish prey. The seasonal and diel activity patterns of goosandersMergus merganser and gulls (Larus canus, L. argentatus, andL. fuscus) were closely related to that of the river lampreyLampetra fluviatilis. During the peak spawning of the river lamprey, birds showed a nocturnal peak in fishing activity. During the summer solstice, birds were active for 24 h. The activity patterns of red-breasted merganserMergus serrator, ternsSterna spp., and three-spined sticklebacksGasterosteus aculeatus were also similar. Activity pattern of the prey apparently influenced breeding time, diel activity and foraging area of the twoMergus species. Social relations between gulls probably corrdinated their peak in fishing, which coincided with the time lampreys were most efficiently exploited.     

Combining limnological and palaeolimnological approaches in assessing degradation of Lake Pskov

Historical spawning grounds for sea lampreys (Petromyzon marinus L.) in most Portuguese river basins are becoming inaccessible due to the construction of impassable dams and/or weirs. Studies like the one described in this paper are particularly important in areas like the Vouga river basin, where there is a considerable fishing effort from both professional fishermen and poachers. In fact, for management and conservation purposes, it is important to clarify several aspects of the sea lamprey spawning run in this particular watershed. Therefore, a total of 30 radio tagged, migrating sea lampreys were released in the River Vouga and some of its main tributaries during 2004 and 2005. Results from the tracking sessions were used to determine the effect of poaching on the spawners’ population and the characteristics of the resting sites used during the upstream movement. The rivers’ stretches were also characterized according to the type of substrate present in the riverbed and flow type, in order to determine its aptitude to constitute appropriate spawning habitats for sea lampreys. We have identified in the upstream stretches of River Vouga, and in the tributary River Caima, characteristics that are particularly suitable for the construction of nests by the spawners. Presence of larvae provided evidence that spawners migrated into the River Vouga’s upper reaches. However, abundance and age class diversity appeared to be higher downstream of Sernada and Carvoeiro weirs, corroborating the telemetry data which suggested difficulty in passing these obstacles during low precipitation years. In the River Caima, migration was most predictable, which might be related to daily water releases from a small hydropower dam at dusk, that stimulated the lampreys to resume migration. Poaching has had a considerable negative effect on the success of the tagged lampreys’ migration: 76% of the animals released during 2005 were captured. Electronic supplementary material  Supplementary material is available for this article at and accessible for authorized user     

Nutritional status of adult sea lamprey (Petromyzon marinus Linnaeus, 1758) during spawning migration in the Minho River,NW Iberian Peninsula

The anadromous sea lamprey (Petromyzon marinus) stop feeding during spawning migration; following the migration effort, the energy reserves of their tissues are expected to be mobilised and depleted. The present work aimed at testing if mobilisation of nutrients occurred in sea lampreys during the 2011 spawning run in the Minho River. Professional fishermen at three sampling sites captured the individuals used: two at the beginning of the freshwater spawning migration (one at the river mouth and one upstream the estuary) and one near the spawning grounds (35 km upstream the estuary limit). The total lipids (Folch extraction), protein (nitrogen conversion), energy content (direct calorimetry) and fatty acids (GC/EI‐MS‐SIM) were determined in the carcass (n = 19) and female liver (n = 8) and gonads (n = 8). The results indicated that a reduction of carcass dry matter during migration was mainly caused by a lipid decrease (51.0 ± 2.46% downstream and 38.0 ± 2.92% upstream, LSmean ± SE). In females, a decrease in the measured amounts of liver lipids was also observed (4.28 ± 2.637 g downstream and 0.64 ± 2.206 g upstream, LSmean ± SE) and the monounsaturated fatty acids consistently composed the larger fraction of lipids in all tissues (ranging between 42.9 ± 4.20% and 54.9 ± 3.43% of total fatty acids, LSMean ± SE). The results suggest a dynamic nutrient mobilisation and the major importance of liver fatty acids (such as 14:1n‐5 and 16:1n‐7) as possible energy sources for embryonic development or combustion during spawning migration. The P. marinus individuals captured at the intermediate sampling site (approximately 35 km upstream river mouth) in the middle of the season seemed as ready to spawn as the upstream sea lampreys.     

Spawning ecology of the American brook lamprey, <Emphasis Type="Italic">Lampetra appendix</Emphasis>

Synopsis We observed spawning American brook lamprey, Lampetra appendix, in coldwater streams in Minnesota to assess various aspects of their spawning behavior and spawning habitat requirements. Spawning occurred during April and May, at water temperatures ranging from 8.7 to 15.5°C. Average adult lamprey length and mass differed significantly among streams, but there were no significant differences in length or mass between males and females. Overall sex ratio was 1:1, although one stream had significantly more males than females and one stream held significantly more females. Lampreys spawned in groups of 2–14 individuals, averaging 4.2 adults per nest across all streams. Nests were constructed in gravel and cobble substrate just upstream of riffles, spaced at an average density of three nests m⁻². The typical nest was 16 cm in diameter in water 31 cm deep with a bottom current velocity of 14 cm s⁻¹, and was excavated to a depth of 4 cm below the stream bottom; however, some nest characteristics varied significantly in a few streams. Nests were larger in streams with larger spawning groups, deeper water, and slower current velocities. American brook lamprey exhibited spawning behaviors and spawning habitat requirements similar to those of other species of lamprey in North America.     

Morphological analysis of geographic variation of sea lamprey ammocoetes in Portuguese river basins

The main objective of this study was to compare the morphological variability of sea lamprey (Petromyzon marinus L.) larvae from the main Portuguese river basins. Samples were collected in rivers Minho, Lima, Cávado, Vouga, Mondego, Tejo and Guadiana. Specimens were analysed in terms of morphometric (linear body measures) and meristic (number of myomeres) characters to investigate the hypothesis of population fragmentation between river basins caused by some degree of homing behaviour. The discriminant analysis showed a morphological segregation of the studied populations based on the characters head, tail and branchial length. The discriminatory power of the meristic characters was comparatively weaker, with the number of trunk myomeres, and to some extent the head myomeres, being responsible for the reduced separation between groups. Both analyses were consistent in identifying the cephalic region as the most important morphological feature to discriminate populations of sea lamprey larvae in the Portuguese territory. The largest cephalic region of the ammocoetes sampled in the northern river basins may be responsible for a better feeding efficiency and, consequently, higher values of condition factor. Guest editors: S. Dufour, E. Prévost, E. Rochard & P. Williot Fish and diadromy in Europe (ecology, management, conservation)     

青海湖裸鲤自然产卵场的生境特征及无人机遥测判别——以泉吉河为例

自然产卵场是维持物种延续最关键的栖息地,青海湖裸鲤（Gymnocypris przewalskii）的自然繁殖栖息地状况和生境特征尚缺乏详细的定量研究。以青海湖入湖河流泉吉河为例,在平水期采用现场调查和无人机遥测的方法对青海湖裸鲤的自然产卵场分布及生境状况进行调查,确定其产卵场生境特征参数,建立基于无人机遥测识别产卵场的方法并进行复核验证。结果表明：泉吉河河道形态可分为弯曲型、分汊型和顺直型等三种典型河型,青海湖裸鲤自然产卵场主要分布在弯曲型和分汊型河道中,分汊型河道几乎100%都有产卵场分布,弯曲型河道有70%为产卵场;产卵场河道平均长度（135.13±61.13） m,平均宽度（30.01±17.51） m,平均曲折度1.09±0.07;平均面积（4586.6±4201.61） m²;产卵场常位于缓水浅滩处,平均水深（0.19±0.10） m （范围：0.03-0.44m）,平均流速（0.24±0.20） m/s （范围：0.01-0.81m/s）,河床质为含有沙粒的卵石（粒径：163-256mm）底质。河道形态、沙洲分布、水深特征等特征参数可作为无人机遥测识别产卵场的判断条件,并实现验证成功。研究结果可为开展整个流域的青海湖裸鲤自然产卵场现状评估及保护对策制定提供技术支撑。     

Stellate cells storing retinol in the liver of adult lamprey,Lampetra japonica

Summary Distribution, localization and fine structure of the stellate cells in the liver of lamprey, Lampetra japonica, were studied during the spawning migration by use of Kupffer's gold-chloride method, fluorescence microscopy for vitamin A (retinol) and electron microscopy. The stellate cells in the lamprey liver differ in some of their properties from those in mammalian livers. Stellate cells which store abundant retinol in lipid droplets, occur not only in the hepatic parenchyma, but also in the dense perivascular and capsular connective tissue of the liver and in the interstitium of pancreatic tissue. In the hepatic parenchyma these cells are located perisinusoidally or along thick bundles of collagen fibrils. The stellate cells display a number of large retinol-containing lipid droplets, granular endoplasmic reticulum, tubular structures, dense bodies, Golgi complex, microtubules, and microfilaments. In the space of Disse, the stellate cells and extracellular fibrilar components such as collagen fibrils and microfibrils (11–12 nm in diameter) are intervened between the two layers of basal laminae. Differentiation and possible functions of the stellate cells in the lamprey liver are discussed.     

Reproductive Biology of Three Commercially Important Hemiramphid Species in South-eastern Australia

Synopsis The reproductive biology of eastern sea garfish Hyporhamphus australis, eastern river garfish H. regularis ardelio, and snub-nosed garfish Arrhamphus sclerolepis were described throughout their respective ranges in the coastal waters of New South Wales (NSW), Australia. Peaks in gonadosomatic indices indicated that spawning of eastern sea garfish occurred in late spring and early summer (November–December) on the south coast of NSW, and in winter and early spring (June–September) on the north coast. Eastern river garfish spawned between July and December in NSW estuaries and snub-nosed garfish spawned between October and January in the Clarence River. The sex ratios in commercial catches of eastern sea garfish from the north coast of NSW were biased toward male fish, but approached equality for fish caught from the south coast. Sex ratios were significantly biased toward female snub-nosed garfish, and female eastern river garfish from all estuaries sampled. Mean (±SE) batch fecundity was 1498 ± 110 (range: 98 – 3449) ripe oocytes per female for eastern sea garfish, 917 ± 36 (range: 102 – 2268) ripe oocytes per female for eastern river garfish, and 716 ± 104 (range: 20 – 2956) ripe oocytes per female for snub-nosed garfish across the range of mature sizes examined. There was a linear relationship between batch fecundity and fish size for all three species of garfish. Eastern sea garfish approached 50% maturity at a larger size than snub-nosed, or eastern river garfish. Size at 50% maturity was similar for male and female eastern river and snub-nosed garfish, but male eastern sea garfish matured at a significantly smaller size than females. All three species appear capable of spawning in the spawning season immediately following the one in which they were born. Mature female fish of all three species had distributions of oocyte diameters consisting of three or four modes, which strongly suggests asynchronous oocyte development and a multiple spawning strategy during the spawning season. Implications for the management of garfish fisheries in NSW are also discussed.     

Long‐term studies on restoration of Connecticut River anadromous sea lamprey,Petromyzon marinus Linnaeus 1758: Trend in annual adult runs,abundance cycle,and nesting

This study is the first to evaluate the results of 60 years of restoring anadromous sea lamprey, Petromyzon marinus, to historical spawning and rearing habitats using fish passage at barrier dams in the Connecticut River, USA. We obtained counts of pre‐spawning adult P. marinus annually passed upstream at Holyoke Dam (river km 140), Connecticut River, MA, during 37 years (1978–2014), and we counted P. marinus nests during 25 years (1986–2010) in the Fort River, a tributary upstream of Holyoke Dam. These two data sets were used to study relationships between adult passage and subsequent nesting and to study nesting timing and ecology. During the 37 years, annual adult P. marinus abundance at Holyoke Dam ranged from 15,000 to 95,000, but regression analysis found no trend (p = .50) for increasing annual adult abundance with years. However, during the 37 years, adults gained access via fish passage at dams to an estimated double the amount of spawning and rearing habitat upstream compared to the 1970s. The lack of a trend for increased adult abundance is consistent with a hypothesis of non‐natal river homing by adults. However, the lack of a trend in adult abundance, when many more larvae are likely present in the watershed compared to the 1970s, is inconsistent with the hypothesis that greater numbers of larvae (and greater concentration of larval pheromone) results in greater number of adults attracted to a river. Instead of an abundance trend of adults with years, we found a rare life history phenomenon occurs in anadromous adult P. marinus ─ an abundance cycle with peaks at 6 year intervals (autocorrelation analysis, p = .04). Comparison of passage timing with nesting timing found passage did not affect nesting initiation or duration (p = .61). Annual date of nesting initiation strongly affected the duration of nesting with earlier nesting resulting in longer nesting (p = .001). Time series comparing Fort River temperature and discharge with nesting found these factors did not clearly predict annual initiation of nesting. This suggests a role for day length (photoperiod) as the trigger for nesting initiation (most nesting began annually during 1–14 June, all year mean, 7 June), regardless of river conditions. However, river discharge may affect nesting ecology because most nesting occurred during decreasing discharge when variability in daily discharge was small (stable discharge). The present research on passage and nesting contributes to a new Connecticut River restoration program for P. marinus, which is a keystone fish species in the watershed.     

Diel activity and thermoregulatory behavior of a fully aquatic frog: Xenopus laevis

Ten adult Xenopus laevis were tested individually for 48-hr periods, following an initial 24-hr introductory period, in electronic shuttleboxes which allowed them to control water temperatures without operant conditioning. Locomotor activity was recorded via photocell-monitored light beams. The frogs were nocturnal, being nearly twice as active at night as during the day. The mean preferred temperature was 22.4°C, with no significant difference between night (22.5°C) and day (22.3°C), although the modal preferendum shifted from 24°C by day to 22°C at night, with a corresponding change in skewness. The range of voluntarily occupied temperatures was 14–32°C by day and 14–29°C at night. The median thermal preferendum was 22°C both day and night.     

Spawning activities and physical characteristics of the spawning ground of Lethenteron reissneri at the headstream of the Himekawa River, central Japan

 The spawning period of the Far Eastern brook lamprey, Lethenteron reissneri, in the headstream of the Himekawa River is estimated to be between mid-March and late May with the peak of spawning activity between early April and early May. The sex ratio (female:male) in 1999 ranged from 1 : 2.5 to 1 : 3.0 (mean 1 : 2.8) and in 2000 from 1 : 0.8 to 1 : 4.0 (mean 1 : 2.4). In >90% of the observations of spawning nests, males outnumbered females. The construction area of spawning nests tended to shift upstream during the spawning period. The nests were constructed at water depths between 5 and 70 cm, water velocity between 10 and 30 cm/s, and on substrate with pebbles of 5–20 mm in diameter. Lethenteron reissneri constructed nests on substrate similar with Petromyzon marinus, but at shallower points and in areas with a slower water velocity. Received: April 2, 2001 / Revised: December 12, 2001 / Accepted: December 27, 2001     

三峡蓄水以来葛洲坝下中华鲟产卵场河床质特征变化

中华鲟是国家一级保护水生动物,是产底层产粘性卵鱼类。河床质构成了中华鲟受精卵和早期胚胎发育的物理环境,其变化可能直接影响中华鲟自然繁殖的规模和效果。基于水声学和水下视频技术对葛洲坝下现存唯一已知中华鲟自然产卵场的河床质特征进行了连续观测,对三峡水库蓄水以来中华鲟自然产卵场的河床质特征变化进行了研究。水声学分析结果显示,2004-2012年间,中华鲟产卵场区域内河床硬度未有明显变化,但粗糙度显著增加 (P < 0.05)。对产卵位点的河床质特征分析表明,下产卵区的硬度增加(2012年显著高于2008和2004年 (P < 0.05)),上产卵区硬度呈明显下降趋势(2004年显著高于2008和2012年(P < 0.05));上产卵区的河床粗糙度均呈不显著上升趋势(P > 0.05);下产卵场区的河床粗糙度呈显著上升趋势(P < 0.05)。水下视频观测结果显示,三峡蓄水导致的水体含沙量明显减少,对河床的冲刷日益明显,表现在产卵场江段沉积细砂和粗砂区域面积显著减少,河床卵石缝隙充塞度明显下降 (P < 0.05)。下产卵区在2007-2012年视频观察过程中发现河床卵石缝隙充分暴露,几乎没有任何细砂或粗砂填充,与上产卵区河床卵石缝隙充塞度特征明显不同。长期观测表明,2004-2012年期间中华鲟自然产卵位点发生了明显的改变,2004-2007年均发生在下产卵区,而2008-2012年均发生在上产卵区,自然繁殖规模和效果也明显下降。综合分析显示,中华鲟产卵场河床质特征的变化可能是导致中华鲟自然产卵位点的改变和迁移的原因,进而影响中华鲟自然产卵场的繁殖适合度,影响中华鲟自然繁殖的规模和效果。对三峡蓄水清水下泄的生态影响评估以及中华鲟自然产卵场的改良或修复有重要借鉴意义。     

Metabolic responses to exhaustive exercise change markedly during the protracted non-trophic spawning migration of the lamprey <Emphasis Type="Italic">Geotria australis</Emphasis>

Adults of the Southern hemisphere lamprey Geotria australis were subjected to an exercise/recovery regime at the commencement and end of their 12–15 month non-trophic, upstream spawning migration. In early (immature) migrants and pre-spawning females, muscle glycogen was markedly depleted during exercise, but became rapidly replenished. As muscle lactate rose during exercise and peaked 1–1.5 h into the recovery period, and therefore after muscle glycogen had become replenished, it cannot be the direct source for that replenishment. However, both plasma lactate and glycerol (but not muscle glycerol and glucose) rose sharply during exercise and then declined markedly during the first 0.5 h of recovery and thus exhibited the opposite trend to that of muscle glycogen, implying that these limited pools of glycogenic precursors contribute to glycogen replenishment. Although plasma glucose rose following exercise, and consequently could also be a precursor for muscle glycogen replenishment, it remained elevated even after muscle glycogen had become replenished. While resting pre-spawning females and mature males retained high muscle glycogen concentrations, this energy store became permanently depleted in females during spawning. In mature males, muscle glycogen remained high and lactate low during the exercise/recovery regime, whereas muscle glycerol declined precipitously during exercise and then rose rapidly. In summary, vigorous activity by G. australis is fuelled extensively by anaerobic metabolism of glycogen early in the spawning run and by pre-spawning females, but by aerobic metabolism of its energy reserves in mature males.