甘露醇和甘油对白斑狗鱼精子活力的影响

为了提高白斑狗鱼精子的受精能力,采用载玻片悬滴法探讨了甘油和甘露醇对白斑狗鱼精子活力的影响。结果表明,白斑狗鱼精子在甘油和甘露醇溶液中活动的最适渗透压在411~616kPa。在411~616kPa甘油溶液中白斑狗鱼精子的快速运动时间最高为85.01±5.09s,寿命时间最高为116.12±7.39s。在411~616kPa甘露醇溶液中白斑狗鱼精子的快速运动时间最高为75.59±3.67s,寿命时间最高为120.33±17.27s。在甘油和甘露醇溶液中,白斑狗鱼精子FT和LT的变化规律基本一致。     

Changes in the flagellum morphology of intact and frozen/thawed Siberian sturgeon Acipenser baerii (Brandt) sperm during motility

Morphological investigations on the changes in flagellar beating was carried out on native (taken from the milt) and thawed sperm of the Siberian sturgeon Acipenser baerii (Brandt). Immediately after activation, the pattern of flagellar wave formation and distribution was the same in native and thawed sperm but, after 27–42 s, depending on the samples, the thawed flagella showed asymmetric and poorly developed waves. The swimming trajectories recorded during 1‐s exposure were much shorter in thawed than in native sperm after 26–28 s motility. In native sperm, the flagella remained in the same axis as the head during the entire motility course, while the head of thawed sperm showed a right angle after 47 s. It is concluded that the freezing/thawing procedure induces some alteration in the dynamics of flagellar beating in many sperm, but these sperm still show progressive displacement. Therefore, the change in morphology of the flagellum during motion is a parameter that should be taken into account in the evaluation of the impact of various treatments on sperm motility.     

Changes in Atlantic cod (Gadus morhua L.) sperm quality during the spawning season

The biology of cod reproduction is well described in the scientific literature. However, sperm biology and spermatozoa management are poorly studied in this species. Because of its recent farming expansion, a better knowledge of cod gametes is becoming especially useful. This work aimed at establishing tools to study sperm biology in cod, and also investigated the existence of changes in cod sperm quality during the spawning period. We showed that sperm concentration could be assessed using spectrophotometry at 260 nm. Sperm motility significantly decreased after a 168‐h storage at 4 °C. A 1:9 dilution of sperm in a non‐activating medium (1/3 seawater and 2/3 freshwater, osmotic pressure: 360 mOsm kg^?1) improved sperm storage. Sperm concentration, sperm velocity and storage capacity at 4 °C peaked during the medium period of the spawning season and then decreased to values close to those observed at the beginning of the reproductive period. The measured values of osmotic pressure, pH, protein, Na⁺, Cl^? and Ca²⁺ concentrations of the seminal fluid were modified along the spawning period. Cell damage was noted at the end of the spawning period: local blebs were observed on the flagellum but also loops at its distal part. On the other hand, spermatocrit did not vary with the sampling date. In conclusion, cod sperm quality is modified during the spawning period, the highest‐quality samples being collected during the medium part of this season.     

Effect of individual male variability on cryopreservation of northern pike, Esox lucius L., sperm

Milt from individual males of northern pike, Esox lucius L., was separately cryopreserved. Concentration of spermatozoa in fresh milt and spermatozoa motility before freezing and after thawing was evaluated. Activity of aspartate aminotransferase (AspAT, E.C. 2.6.1.1.) and acid phosphatase (AcP, E.C. 3.1.2.2.) in fresh and thawed sperm were determined. In comparison with the control group, egg fertilization with cryopreserved milt varied from 6.6% to 96.0%, depending on the donor male. Fertilization success with cryopreserved pooled milt was 71.8%. Freezing and thawing procedure caused loss of proteins from injured spermatozoa, resulting in significantly lower enzymatic activity in spermatozoa. Intensity of enzyme leakage in thawed milt correlated negatively with fertilization success. Concentration of spermatozoa could be a possible accessory quality indication, useful when selecting sperm samples appropriate for cryopreservation.     

Protracted spawning of St Lawrence River northern pike (Esox lucius): simulated effects on survival, growth, and production

Abstract –  An individual-based early life history model demonstrated that the timing and distribution of St Lawrence River northern pike ( Esox lucius ) spawning could affect subsequent young-of-year (YOY) production during nursery and influence year-class formation. Three different spawning patterns have emerged from empirical studies, where egg deposition occurred along the entire littoral gradient beginning in seasonally flooded emergent habitats in tributaries, progressing to submerged aquatic vegetation in shallow bays, and ending in deep water littoral habitats (up to 6 m). The spawning period is protracted, and typically lasts 6–8 weeks due to the presence of a strong thermal gradient. The model used temperature as the driving variable to predict egg abundance, stage-specific development, growth, survival, and ultimately relative production of YOY northern pike within 1-ha plots representative of the three habitats. Earlier spawning (mean 21 days) and higher mean daily survival and growth yielded higher YOY net production for tributaries (mean = 3095.4 g ha⁻¹, SD = 2028.6) relative to the shallow bay habitat (202.5 g ha⁻¹, SD = 125.7). In contrast, deep littoral habitat represented an ecological sink with little production (<0.9 g ha⁻¹). The results demonstrate the importance of the linkage between spawning and nursery processes in determining reproductive success.     

Hatching time effect on the intra‐spawning larval morphology and growth in Northern pike (Esox luciusL.)

Based on the analysis of 11 morphometric variables of body (total length, body area and perimeter, myotome height and eye diameter) and yolk sac (length, height, area, perimeter and volume) of pike larvae, the aim of this study was to evaluate how larval size at hatching and growth of larvae hatched from single egg batches vary according to three hatching times: early, mid and late. Hatching time structures strongly pike larval morphometrics. Early hatched larvae have smaller body sizes at hatch, faster growth and higher yolk use efficiency than late hatched ones. Early hatched larvae seem to be premature and hatch at precocious developmental stage whereas late hatched individuals continue their growth within the egg shell and hatch at larger size but with lower reserves (yolk). A compensatory growth phase was observed for the early hatching pike larvae particularly during the first 5 days post hatch. Consequently, no significant difference in body parameters was recorded from day 10 post hatching whatever the hatching time. The higher growth accomplished by early hatched larvae may be related to a particular metabolic activity that converts more efficiently yolk into body tissues.     

A study of the dynamics of volume changes during the period of active motility in carp, Cyprinus carpio L., spermatozoa

Carp, Cyprinus carpio L., spermatozoa swelling in NaCl hypotonic solutions (18.8, 37.5, 75, 100 mM) was studied by the methods of photometry and resistance impulses spectroscopy (RIS). The possibility of application of the value of relative optical density of cell suspension, as a qualitative characteristics of the extent of spermatozoa swelling in the period of their movement, was demonstrated. It has been noted, that the moment when swelling starts coincides with the moment of the start of sperm motility. Movement duration, extent and time of swelling depend on the osmotic pressure of the activation solution and moreover the maximum motile period is observed during the activation by 75 mM NaCl solution.     

Changes in northern Tanzania coral reefs during a period of increased fisheries management and climatic disturbance

• 1. Surveys of coral reefs in northern Tanzania were conducted in 2004/5 with the aim of comparing them over an～8‐year period during a time of increased efforts at fisheries management and the 1998 El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) coral mortality event that caused 45% mortality in northern Tanzania and much of the Indian Ocean.
• 2. Changes associated with both management, its absence, and the ENSO were found but changes were generally small and ecological measures indicated stability or improvements over this period, particularly when compared with reports from much of the northern Indian Ocean.
• 3. Fisheries management in two areas increased the biomass of fish and benthic communities. A small fisheries closure (0.3 km²) displayed little change in the coral community but ecological conditions declined as measured by sea urchins and fish abundances. This change may be associated with its small size because similar changes were not measured in the large closure (28 km²).
• 4. The few sites without any increased management were still degraded and one site had experienced a population explosion of a pest sea urchin, Echinometra mathaei.
• 5. The lack of significant changes across this disturbance indicates that these reefs are moderately resilient to climate change and, therefore, a high priority for future conservation actions.

Copyright © 2009 John Wiley & Sons, Ltd.     

The effects of mechanically reducing northern pike density on the sport fish community of West Long Lake, Nebraska, USA

Abstract  Removal of piscivores may affect population size structure, abundance and growth rates of the remaining fish community. A total of 572 northern pike, Esox lucius L., was removed from 25-ha West Long Lake, Nebraska from 2003 to 2006. The northern pike population was reduced from 36 fish ha⁻¹ and 22 kg ha⁻¹ in 2002 to 20 fish ha⁻¹ and 9 kg ha⁻¹ in 2006. The northern pike population shifted to dominance by smaller individuals. Relative abundance increased for bluegill, Lepomis macrochirus Rafinesque, but remained similar between years for largemouth bass, Micropterus salmoides (Lacepède), and yellow perch, Perca flavescens (Mitchill). Bluegill and yellow perch size structure increased probably because of reduced predation by northern pike. The effects of reduced northern pike density on largemouth bass were less evident. The largemouth bass population may be returning to higher density with smaller size structure observed before pike were introduced. The sport fish community responded positively to the removal of northern pike in this small lake.     

Vegetative substrates used by larval northern pike in Rainy and Kabetogama Lakes,Minnesota

Our objective was to identify characteristics of aquatic vegetative communities used as larval northern pike nursery habitat in Rainy and Kabetogama lakes, glacial shield reservoirs in northern Minnesota. Quatrefoil light traps fished at night were used to sample larval northern pike in 11 potential nursery areas. Larval northern pike were most commonly sampled among floating‐leaf burreed Sparganium fluctuans, common burreed Sparganium eurycarpum, sedges Carex spp., hybrid cattail Typha × glauca and wild rice Zizania palustris. A negative binomial model of light‐trap catches using the presence/absence data for 2012 from all 11 bays included water elevation and the presence of cattail as significant variables. Ultimately, the species of vegetation may not be as important as the physical quality or form of the vegetation in supplying feeding and hiding cover. The aquatic plant species and structural forms encountered by larval northern pike suggest they use nearly any vegetated cover available in early spring. Water‐level regulations that change availability of aquatic vegetation are likely to influence recruitment of northern pike to larger sizes.     

Habitat of pike gudgeon Pseudogobio esocinus esocinus in Nakagawa River, northern Kyushu, Japan

ABSTRACT:   Habitat selection of the pike gudgeon Pseudogobio esocinus esocinus (Cyprinidae) was examined in the Nakagawa River in northern Kyushu, Japan. The study area was 80 m long with two meanders comprising three riffles and two pools, located 20 km upstream from the river mouth. The pike gudgeon were visually counted underwater. Larvae and juveniles were observed in the shallow and slow-flowing water near the shores. Simultaneously, young and adult individuals were observed to inhabit the river bed. Principal component analysis and cluster analysis were applied to estimate the microhabitat selections of the larvae, juveniles and other individuals by using four variables (water depth, current velocity, particle size of substrate and amount of organic matter). The larvae and juveniles inhabited the shallow (<30 cm) and slow-flowing waters (<6.5 cm/s) near the shore; habitat selection was independent of particle size of the substrate and the amount of organic matter present. Young and adult individuals inhabited the river bed independent of the four variables.     

Mitochondrial DNA variation in two samples of northern pike, Esox lucius L.

The mitochondrial genotype of northern pike, Esox lucius L., was characterized by restriction analysis performed over the entire mtDNA molecule (33 fish) and over a ～1.4-kb PCR-amplified segment of a mitochondrial non-coding control region (six fish). Out of eight restriction endonucleases used in the present study of the entire mitochondrial genome, the Nco I and Pst I enzymes produced variant fragment patterns which allowed identification of three mitochondrial genotypes. Low mtDNA diversity was shown by estimates of pairwise nucleotide substitution values (d; mean ± SE = 0.49 ± 0.43%), haplotype diversity (h= 0.16) and the nucleotide diversity index (π= 0.06%). The present authors developed a PCR protocol for mitochondrial DNA non-coding control region to search for more variation. Whereas the PCR assays revealed distinct length variation in this mtDNA segment, restriction analysis performed with three additional restriction enzymes showed no variability which could be attributed to a gain or loss of a particular restriction site. Although the mtDNA analysis proved ineffective in genetic discrimination between the two northern pike samples studied, fish with rare mtDNA genotypes could be used for conducting experimental genome engineering or stocking studies with this species.     

Protease in sturgeon sperm and the effects of protease inhibitors on sperm motility and velocity

In mammals, proteases are present in sperm acrosome and play key role in fertilization. Sturgeon sperm has an acrosome, but its physiology, biochemistry, and potential role in fertilization are unknown. In the present study, we have observed high protease activity in acidic extract of intact sperm compared to that of seminal plasma in sterlet (Acipenser ruthenus). The protease activity was decreased and increased in acidic extract of motility-activated sperm and in the activation medium, respectively. Molecular analysis revealed total protease and serine (acrosin) protease activities in sperm acidic extract which was accumulated in a protein band with relative molecular mass of 35 kDa. Immunoelectron microscopy using an affinity-purified polyclonal antibody for boar acrosin localized the protease at the acrosome region. Moreover, initiation of sperm motility was inhibited after activation in the presence of inhibitors for both trypsin-like and chymotrypsin-like proteases, while the effects of protease inhibitors on sperm velocity were uncertain. Our results indicate similarities in physiology and biochemistry of acrosome between sturgeon and mammals and suggest potential role of protease in the initiation of sperm motility in sturgeon.     

Short-term salinity tolerance of northern pike, Esox lucius, fry, related to temperature and size

Abstract  The short-term tolerances of northern pike, Esox lucius L., fry reared in a freshwater hatchery, to salinity were examined in the laboratory. Survival of two size groups of pike fry (mean length 21 ± 2 mm SD and 37 ± 4 mm SD) was examined over 72- to 96-h periods at 9–14 ppt salinity in combination with temperatures of 10, 14 and 18 °C. A parametric survival model found a significant correlation between survival of pike fry and temperature and salinity, respectively. L _C50 values after 72 h were between 11.2 and 12.2 ppt, being lowest at 10 °C. Pike fry did not survive more than 13 ppt. Mortality at 12 ppt was significantly faster at 18 °C than 10 or 14 °C. Moreover, mortality was higher and faster for large than for small pike fry at 12 ppt and 14 °C. These results imply that pike raised in fresh water can survive stocking into brackish waters below 11 ppt at least for a short time.     

不同密度白斑狗鱼受精卵孵化率及初孵仔鱼成活率比较

2009年4-5月在河北省赞皇县正和水产良种有限公司,进行了白斑狗鱼规模化全人工繁育技术研究。对不同密度受精卵孵化率及初孵仔鱼成活率进行了比较研究,结果表明:受精卵孵化密度在8 000~15 000粒/槽较为适宜,最佳密度为10 000~13 000粒/槽;初孵仔鱼培育密度10 000~15 000尾/m3水体较为适宜,最佳密度为11 000~13 000尾/m3水体。     

Oocyte and embryo quality in Crassostrea gigas (Portuguese strain) during a spawning period in Algarve,South Portugal

Egg quality is one of the most important factors determining larval viability. The study of oocytes released by `wild' broodstock will contribute to the definition of quality criteria applied to hatcheries as well as being an indicator of the oyster reproduction potential and aquaculture ongrowing systems. The aim of this study was to determine the relationship between condition of Crassostrea gigas spp. angulata (Portuguese strain) from `wild' broodstock (condition index, gonadal maturity and number of oocyte released), oocyte biochemistry and hatching rate of eggs during the spring/summer of 1995. Stages of gonadal maturity and condition index indicated that natural spawning of this species occurred between April and August with the highest spawning intensity occurring in June. Analyses demonstrated that C. gigas oocyte organic matter consist of 44–74 % proteins, 16–38 % lipids and 7–12 % carbohydrates. A significant relationship was observed between some biochemical parameters – organic matter and lipid content – and broodstock condition index and hatching rate. It seems that these two oocyte parameters (organic matter and total lipids) could be used to define quality of oocyte and thus larval viability. The oocyte protein content was also found to be associated with broodstock and larval quality. In summary, these data are a contribution to the knowledge of the reproductive cycle of oysters in Europe and may be useful in improving hatchery management of this species.     

An efficient method for cryopreservation of testicular sperm from the Northern pike, Esox lucius L.

The cryopreservation of semen from the Northern pike, Esox lucius L., was investigated with a method that was originally developed for the Salmonidae. Because the amounts of semen obtained by stripping were insufficient, the suitability of testicular sperm was tested for cryopreservation. Frozen-thawed testicular sperm had fertilization rates similar to frozen-thawed semen obtained by stripping (74.2-84.7%), and at sperm to egg ratios of S= 4.5 × 10⁵ spermatozoa per egg, the post-thaw fertilization rates were also similar to fresh, untreated semen controls. Out of all the fertilization solutions investigated, a 100-mm NaCl, 10-mm Tris (pH 9) solution resulted in the highest post-thaw fertilization rates. To facilitate the fertilization of large egg batches, 1.2-mL straws were used for cryopreservation with a similar efficiency to 0.5-mL straws.     

Physiological effects of ice‐angling capture and handling on northern pike,Esox lucius

Understanding how released fish recover following capture is vital information for researchers examining the effects of angling on exploited populations. This information is virtually non‐existent for fish angled through the ice in winter, despite the popularity of ice‐angling in many northern areas. To address this gap, 60 northern pike, Esox lucius L., were angled through the ice from an impoundment in eastern Wisconsin, USA, and subjected to one of ten combinations of handling and recovery duration. Plasma samples were collected and analysed for cortisol, lactate and glucose. The results showed a delayed response in the elevation of plasma variables, and a significant interaction between air exposure and recovery time for plasma lactate. No fish suffered mortality during the period of holding. Collectively, these data suggest that northern pike are physiologically resilient to ice‐angling capture stress as long as air exposure times are kept at 4 min or less.     

黄鳝精子活力检测和精子入卵早期过程观察

采用Olympus3×51相差系统显微镜和SQIAS—1000彩色精液质量图文分析系统检测黄鳝精子活力。结果表明,在NaCl溶液浓度为0～0.3%时,黄鳝精子激活比例随溶液浓度升高而极显著增加(P<0.01);当NaCl浓度达到0.7%时,精子激活比例、直线运动速度和鞭毛摆动频率均显著(P<0.05)或极显著(P<0.01)降低。扫描电镜观察显示:黄鳝成熟卵卵壳膜上的精孔区呈漏斗状凹陷,其底部中央可见一精孔管外孔,口径约4.22±0.66μm;黄鳝精子入卵速度缓慢,受精过程较长,从精子附着于卵球表面到精孔管完全堵塞,约30s～5min。     

High variability in spawning migration of sea trout,Salmo trutta,in two northern Swedish rivers

Abstract Telemetry was used to examine spawning migration of sea trout, Salmo trutta L. (n = 126), in two rivers in northern Sweden. The spawning areas defined by radio‐tagged fish differed between the river systems. In the River Vindelälven, sea trout spawned in the main stem and 80% of tagged individuals returned to areas where hatchery‐reared juveniles had been previously stocked. In the River Piteälven, 74% of tagged sea trout ascended tributaries for spawning. Tagged fish were categorised into three groups of migratory pattern. cart (classification and regression tree) analysis indicated that distance from tagging location to spawning site (S_dist) explained the migratory patterns. Large S_dist separated fish with stepwise upstream migration from those with up‐ and downstream migrations and one‐directional direct migration. Fish tagged early in the season migrated the longest distance to spawning areas. Stocking locations and sex explained the large search behaviour up‐ and downstream in the rivers. The findings are important for the sustainable management of sea trout in the Gulf of Bothnia.