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1.
The effect of freezing and frozen storage of threadfin bream fish (Nemipterus japonicus) meat on the setting and gel-forming ability has been evaluated. The dynamic viscoelastic properties of fish meat during setting and thermal gelation process were evaluated using Controlled Stress Rheometer under oscillatory mode. A sharp decrease in setting ability was recorded immediately after freezing as revealed by storage modulus (G?) values. The transglutaminase (TGase) enzyme activity of fish meat decreased from the initial value of 81.09 to 51.46 U/g meat/min at the end of 200 days of frozen storage. A decrease in setting ability of fish meat beyond 160 days of frozen storage is probably related to lower TGase enzyme activity. The gel-forming ability was related to setting ability during the frozen storage period. Although the protein solubility showed a decreasing trend during 200 days of frozen storage, the decrease was not significant. The effect of freezing and frozen storage on calcium-activated adenosine triphosphatase (Ca2+-ATPase) enzyme activity of fish mince was significant (P < 0.05). A reduction in protein solubility and Ca2+-ATPase enzyme activity is an indication of aggregation/denaturation of myofibrillar proteins.  相似文献   

2.
Abstract:   The question of whether the ovulation and spawning time in chub mackerel Scomber japonicus is entrained by a circadian rhythm was raised by our previous experiments. Further questions were also raised about whether the time course of human chorionic gonadotropin (hCG)-induced final oocyte maturation (FOM) and ovulation reflected the natural time course induced by endogeneous pituitary gonadotropin (GtH). To address these questions, hCG and gonadotropin-releasing hormone analog (GnRHa) were administered at two 'opposite' times, 14:00 and 02:00 hours, and the time courses of FOM and ovulation were compared. When hCG was injected, ovulation occurred 33 h post-injection in both groups, regardless of the timing of the hCG injection. The timing of ovulation in chub mackerel depends on the timing of hCG injection, but apparently not on circadian rhythms. When GnRHa was injected, ovulation began at 36 h post-injection of GnRHa, regardless of the timing of injection. These results indicate that the time course of FOM and ovulation in the chub mackerel followed a similar pattern whether stimulated by hCG injection or spontaneous luteinizing hormone (LH) surge because GnRHa induces the secretion of endogenous GtH (primarily LH) from the fish pituitary. Thus, it is concluded that the time course of hCG-induced FOM and ovulation in chub mackerel follows the natural time course induced by endogenous pituitary LH.  相似文献   

3.
Abstract

Modification of pH during washing showed a beneficial effect on the composition, color and gel-forming ability of Monterey sardine minced flesh. Further improvements in colorand gel-forming ability were achieved by washing under acidic conditions. The proposed washing procedures reduced water usage from 10 to 55% as compared to those used for the washing of dark fleshed fish. Final recoveries after washing were 52% and 49.5% for solids, and 57.4% and 55.8% for protein for acidic and alkaline processes, respectively. Gel-forming ability of mince was compromised as a result of pH modifications. Further studies are required to improve the gel-forming ability of mince by adjusting pH above 6.7 during sol/gel preparation.  相似文献   

4.
Research into artificial reproduction of chub was studied during three subsequent reproductive seasons. Chub reproduction was conducted in two different variations. In the first experiment different hormonal agents were given to fish, such as CPE, hCG, or an analogue of GnRH with dopamine antagonist (ovopel). In the second one, the optimum moment of applying of artificial reproduction was sought and the fish were only obtained an analogue of GnRH in different periods. The results obtained in two first seasons indicated that ovopel is the most effective agent for the artificial reproduction of chub. Consequently, it was decided that the fish would obtain only this agent in the final year of research. In last year (experiment II), chub spawners were taken to the hatchery under controlled conditions every few weeks from February to the beginning of June. Periodically, the maturity of oocytes was checked. As soon as the oocytes had achieved stage 2–3 of maturity, fish were obtained ovopel. It was noted that there was no problem with collecting semen. Obtaining oocytes was much more difficult. Most frequently, they were not obtained at all or obtained in very small amounts. It was also observed that the administration of hormones caused a very quick maturation of gonads and their over-maturation.  相似文献   

5.
Abstract –  We examined macrohabitat patch level assemblage composition and habitat use patterns of fishes over four seasons in a second-order submontane stream (Danube drainage, Hungary). Rainfall data indicated that our study included both high- and low-water periods, and hence our results may be applicable to broader time scales. Principal component analysis of physical habitat data from 13 macrohabitat patches indicated that these patches represented a riffle-pool continuum. Correspondence analysis of fish assemblage structure data from these patches identified a continuum in assemblage composition that was positively correlated with the habitat continuum. The riffle fauna was dominated by stone loach ( Barbatula barbatula ), whereas chub ( Leuciscus cephalus ) were most abundant in pool patches. We detected little evidence of seasonality in either fish assemblage structure or habitat use. Fish density did not differ significantly among macrohabitat patches in two (summer and autumn 1999) of three seasonal samples, although riffle patches displayed significantly higher fish abundance in late spring 2000. This difference primarily was due to higher abundance of juvenile stone loach in riffles. Two species, stone loach and minnow ( Phoxinus phoxinus ), displayed generalized habitat use patterns, whereas chub and rare species (i.e., gudgeon, Gobio gobio ; dace, Leuciscus leuciscus ; Barbus petenyi ; and burbot, Lota lota ) were significantly over-represented in pool habitats. We hypothesized that pool specialists (i.e., chub and rare species) were responding primarily to the increased depth of these habitats. Nevertheless, our data did not demonstrate the presence of separate pool and riffle habitat guilds. In conclusion, we believe that our understanding of stream fish ecology will be greatly facilitated by use of a 'patch-based approach'.  相似文献   

6.
Abstract –  Movements of fish, in particular roach Rutilus rutilus , perch Perca fluviatilis, rudd Scardinius erythrophthalmus, bleak Alburnus alburnus and chub Leuciscus cephalus (age ≥ 1+) in relation to environmental variables were examined between the River Morava, Czech Republic, and a rehabilitated former meander. Data were taken over seven 24-h periods in April–June 1997 using two back-to-back traps. Of 170 fish captured, 70% moved from the backwater to the river. Diel activity differed between sampling dates, but overall bleak, roach and chub moved mainly between dusk and dawn, whereas perch moved throughout most of the day. Rudd showed bi-modal (mid-day, midnight) activity. However, avoidance behaviour could have biased results for species known to be wary of traps. Water level changes, temperature and illumination were among the main environmental factors influencing fish movement, along with spawning migrations relevant for most species. In all specimens, over 65% individuals captured were ready to spawn. Most of them, except for perch, were moving out of the backwater towards the river.  相似文献   

7.
A feeding trial was conducted to investigate the effects of dietary lipid level on growth and body composition of juvenile river chub, Zacco barbata (Regan). Juvenile river chub with 0.26 g body weight were given five isoenergetic and isonitrogenous purified diets containing 0–20% lipids in 5% increments for 8 weeks. The dietary lipid source was a 1:1 (w/w) mixture of menhaden fish oil and soybean oil. There was no significant difference on weight gain, feed conversion ratio, or protein efficiency ratio, among fish fed different experimental diets ( P  > 0.05). Body fat contents of both initial fish and fish fed the diet containing 20% dietary lipid were significantly greater than those fed other diets ( P  < 0.05). The percentage of total n -3 fatty acids in the body lipids of fish at the beginning of the trial was 12.34%. This value decreased to 3.83% by the end of the trial for fish fed a control diet with no supplemented lipid. Similar trends were observed in linoleic acid contents that were 6.11% and 3.09%, respectively, for initial fish and the fish fed the control diet for 8 weeks. However, the absolute amount of these fatty acids stayed the same in the initial and in the control group. Meanwhile, as dietary lipid level increased, the percentages of these fatty acids in body lipids of fish at the end of the trial also increased.  相似文献   

8.
Abstract –  Leatherside chub ( Snyderichthyes copei Jordan & Gilbert) comprises two lineages (northern and southern) whose centres of geographical range differ by about 3° latitude corresponding to about 30% shorter growing season and about 2 °C lower mean temperature during the growing season. We document patterns of variation in size-at-age among populations of leatherside chub in nature, and we test for variation in intrinsic growth rate of juvenile chub in a common-environment experiment to determine if lineages exhibit different intrinsic growth rates. Northern leatherside chubs at ages 1–3 were about 15% shorter in length compared with southern populations. Variation in hatching date or age at maturity could not account for differences in growth and body size, suggesting that temperature-specific intrinsic growth rates differed among populations. Based on a common environment experiment, we found that reaction norms for temperature-specific growth in length and mass were crossed. At the lower temperature, individuals from the north exhibited higher intrinsic growth in length, and at the higher temperature individuals from the south exhibited higher intrinsic growth in mass. Crossing reaction norms for temperature-specific intrinsic growth rates support a model of local adaptation to thermal regime.  相似文献   

9.
Diet interactions between native and non‐native fishes may influence the establishment of native species within their historical range (i.e., reintroduction). Therefore, we illustrated the food web structure of and followed the transition of the federally endangered humpback chub Gila cypha into a novel food web following translocation and determined the potential for a non‐native species, rainbow trout Oncorhynchus mykiss, to influence translocation success. Humpback chub and rainbow trout used resources high in the food web and assimilated similar proportions of native fishes, suggesting non‐native rainbow trout may occupy an ecological role similar to humpback chub. Subsequently, humpback chub may be well suited to colonise tributaries because of their ability to consume resources high in the food web. Additionally, diet partitioning may occur between all members of the fish community as indicated by separation in trophic niche space and little trophic overlap; although all species, particularly bluehead sucker Catostomus discobolus, used a broad range of food resources. Rainbow trout stomach content analysis corroborated stable isotope analysis and suggested rainbow trout diet consisted of aquatic and terrestrial macroinvertebrates, while larger rainbow trout (>120 mm total length) consumed a greater proportion of fish (incidence of piscivory = 5.3%). Trophic interactions may reveal an underutilized niche space or biotic resistance to the establishment of translocated native fishes. Continued translocation of humpback chub into tributaries appears to be one option for conservation. However, successful establishment of humpback chub may depend on continued removal of non‐native trout, increasing availability of diet sources at higher trophic levels.  相似文献   

10.
Xin  GAO  Yuri  TASHIRO  Hiroo  OGAWA 《Fisheries Science》2002,68(3):499-508
ABSTRACT: Changes in tissue structures, rheological properties, and water content of abalone meat were studied in relation to boiling and steaming time. The adductor muscle of abalone Haliotis discus, which was removed directly from the shell, was boiled or steamed for 1 h, 2 h, and 3 h. When observed under a light microscope and by scanning electron microscopy, structural changes in the myofibrils were greatest in the boiled abalone meat compared with the steamed meat. When heating time was increased from 1 h to 3 h, the instantaneous modulus E 0 of boiled abalone meat decreased gradually with increased heating time, whereas the E 0 of steamed abalone meat was reduced when heated for 2 h. When heated for 1 h, the relaxation time of steamed abalone meat was much longer than that of boiled meat. There were no significant changes in the relaxation time of abalone meat among the different boiling times, but the relaxation time of steamed abalone meat was reduced gradually with increasing heating times. The study's results confirmed that the difference in rheological properties between the boiled and steamed meats was due mainly to the denaturation level of myofibrils when heated for 1 h, as well as due to the changes in water and solid content and the manner in which the inner water was exchanged after heating time was increased from 1 h to 3 h.  相似文献   

11.
ABSTRACT:   Final oocyte maturation and ovulation of captive chub mackerel Scomber japonicus with fully yolk-accumulated oocytes were induced by a single injection of human chorionic gonadotropin. Reproductive parameters, including spawning frequency and batch fecundity, which are required to estimate spawning biomass in pelagic fish by the daily egg production method, were analyzed. Germinal vesicle migration (GVM) occurred at 18–24 h post-injection, and the hydration and ovulation of oocytes were completed at 30 and 36 h post-injection, respectively. The results of the maturation process suggest that fish with GVM-stage ovaries captured in the daytime from the field are capable of spawning on the night following their capture. The oocytes used in the oocyte size-frequency distribution method for batch fecundity estimates should be at late GVM and more advanced stages. The results of sequential artificial insemination showed that the quality of ovulated eggs held in the ovarian lumen rapidly deteriorated as time progressed after ovulation. This indicates that the fertilization window for the ovulated eggs of chub mackerel lasts only a few hours, and spawning behavior should be performed within a few hours after ovulation in the wild population.  相似文献   

12.
ABSTRACT:   In order to understand the characteristics of burnt meat in cultured yellowtail Seriola quinqueradiata , fish were kept at two different temperatures (13 and 30°C) and slaughtered by either spinal cord destruction (SCD) or suffocation in air (SA). Early postmortem changes during storage at 32°C were analyzed by rheological, biochemical, and histological methods. The burnt meat (with lightness parameter, L* ≥ 55) was observed at 1-h storage in the SA 30°C group, at 2 h in SCD 30°C, and at 4 h in SA 13°C; meat was normal for the SCD 13°C group until 6 h of storage. Breaking strength scores were higher for the normal meat (200 g/cm2) than burnt meat (70 g/cm2) at 4 h of storage. Expressible water content was higher for the burnt meat than for the normal meat. Adenosine triphosphate concentrations for the SCD groups were higher than for the SA counterparts. Moreover, pH decrease was much faster in the 30°C groups, showing pH 5.6 at 2 h of storage. A negative correlation between the pH and lactic acid contents in muscle ( P  < 0.001) was found. Histological analysis evidenced a larger pericellular area (40%) in the burnt samples than in the normal samples (16%). It was confirmed that a higher fish-keeping water temperature and a stressful slaughter method (faster glycolytic process) were determinative factors that influence the occurrence of burnt muscle in yellowtail, and that the effect of the former is larger than the latter.  相似文献   

13.
Swimming ability and differential use of velocity patches by 0+ cyprinids   总被引：1，自引：0，他引：1  
Abstract– The ability of chub, dace and roach to resist displacement in a laboratory channel was not only controlled by species-specific swimming ability, but also by the fishes'ability to locate areas of reduced velocity. Dace were better able to withstand high velocities than roach. Chub were better at locating slow flowing patches than either roach or dace throughout their early development. Only chub larvae shifted towards slower flowing patches as velocity increased. All juveniles shifted to slower flowing patches at high velocities.  相似文献   

14.
Activity patterns of largemouth bass in a subtropical US reservoir   总被引：1，自引：0，他引：1  
Abstract  Nine largemouth bass, Micropterus salmoides Lacepède, >1.5 kg were implanted with radio tags and tracked for 1 year in an embayment of Lake Seminole, Georgia, USA. Most largemouth bass movement was <50 m h−1 in all seasons and at all times of day. During the day largemouth bass were offshore in deeper water near large woody structures and moved little. Movement was lower during dusk and night periods, and a general movement towards shoreline areas was evident. Water depths where largemouth bass were located had bimodal distributions in all seasons and diel periods, with one mode typically at depths <1 m and another around 3 m. Home ranges were typically largest in the summer and smallest in the winter. Largemouth bass appeared to divide their time between an offshore resting area, primarily occupied during the day, and a near-shore area, where foraging presumably occurred, primarily used during low-light periods. The largemouth bass population in Lake Seminole consists of multiple overlapping subpopulations, offering the opportunity for embayment-specific management.  相似文献   

15.
杨宪时  许钟 《海洋渔业》1996,18(1):13-16
根据我国消费、生产现况和鲐鱼的加工特性，在国内外现有的调味煮品加工技术基础上进行了改进，研制出一种新型调味煮干品－鲐鱼鱼肉干。改进后的工艺特点：（１）将采肉后漂洗改为去皮和去皮下脂肪后采肉，避免了鱼皮、皮下脂肪的混入，省去了漂洗、脱水等复杂的工序和设备；避免了水溶性蛋白质等的流失，提高了成品率。（２）产品熬煮后烘干至水份活度０．７０左右，能在常温下保质四个月以上，避免了传统调味煮熟品高糖高盐、容易  相似文献   

16.
The effect of two commercial preparations containing different GnRH analogues with dopamine antagonists on quantitative and qualitative parameters of semen from chub Leuciscus cephalus L. collected in artificial conditions were examined. Semen was collected after the application of [(D‐Ala6, Pro9 NEt)‐mGnRH + metoclopramide] (Ovopel, n = 9), [(D‐Arg6, Pro9 Net)‐sGnR + domperidone] (Ovaprim, n = 9) and from the control group (0.9% NaCl, n = 9). Afterwards, semen volume, sperm concentration, total sperm production and semen pH were determined. Osmolality and pH of seminal plasma were also determined. Using the Computer‐assisted sperm analysis system (CASA), selected sperm parameters such as sperm motility (MOT %), progressively motile sperm (PRG, %), curvilinear velocity (VCL, μm s?1), straight‐line velocity (VSL, μm s?1), movement linearity (LIN, %), wobbling index (WOB, %), amplitude of lateral head displacement (ALH, μm) and beat cross frequency (BCF, Hz) were analysed. While Ovopel can also be used to stimulate chub spermation, the application of Ovaprim was much more effective for obtaining higher amounts of semen.  相似文献   

17.
Oyster processing sometimes requires determining if the shucking process has been completed. One application of this requirement is in the automated Wheaton oyster shucking machine where one oyster shell valve is removed and it is necessary to determine before the oyster proceeds through the remaining machine components whether the valve has been removed. Failure to remove the valve will cause the oyster meat to be destroyed downstream in the processing system. Thus, an automated sensor was developed to view the oyster and determine automatically if the valve was removed. The sensor is based on the difference in light absorption between the oyster meat and shell. Light reflected from the oyster passing beneath the sensor enters the sensor and passes through a beam splitter. Each light beam passes through a different narrow band filter and into a photocell. The output difference between the two photocells was used to determine if an oyster meat or shell was passing beneath the sensor. The sensor output for the 875 nm shell sensor varied from 0.143 to 0.305 mV and for the 975 nm shell sensor varied from 0.27 to 0.615 mV. When looking at meat the 875 nm sensor output varied from 0.157 to 0.305 mV and the 975 nm sensor varied from 0.307 to 0.622 mV. Results show the sensor will detect the difference between the oyster shell and the meat as long as there are readings for both sensing elements for both the meat and the shell. With the Wheaton shucking machine the design configuration will provide only a wavelength readings for either the meat or the shell but not both. Suggestions are presented to modify the system to allow the sensor to differentiate between the oyster meat and shell.

Because the study was designed to determine if the sensor would perform as designed data on the sensor speed was not available. However, the sensor was designed as part of a shucking machine with a design shucking rate of 60 oyster/min. With the electronic processing needed and the available computer processing power today the sensor should be able to meet the 60 oyster/min for which the shucking machine was designed.  相似文献   


18.
Gelation is an important functional property of protein in meats. In this study, we prepared actomyosin from scallop Patinopecten yessoensis adductor muscles and studied the effects of pH on the physicochemical properties of the actomyosin preparation and on its heat-induced gel-forming properties. The results showed that the turbidity and surface hydrophobicity of scallop actomyosin increased with increases in the heating temperature, while the α-helical content concomitantly decreased. Higher turbidity and surface hydrophobicity and lower α-helical content were found to be easily obtained at lower pH values. A high water-holding capacity, strong gel strength, fine gel network and uniform ice crystals were all clearly observed at pH 7.0, indicating that a neutral pH was most beneficial for formation of the heat-induced scallop actomyosin gel. We therefore conclude that both the physicochemical properties of scallop actomyosin and its gel-forming ability during the heating process are pH dependent.  相似文献   

19.
Small-scale mud carp (SC, Cirrhina microlepis) and common carp (CC, Cyprinus carpio) are underutilized freshwater fish. The objective of this study was to elucidate the gel-forming ability of mince and washed mince from these species in relation to washing cycles and CaCl2 addition. Protein loss of up to 67% was observed after three-washing cycles of both species, rendering relatively low yield. About 85–90% of total fat was removed from SC flesh after three-washing cycles, but only two-washing cycles were sufficient for fat removal in CC mince. Mince and washed mince of both species did not exhibit severe proteolysis with low autolytic activity at 65°C. SC exhibited superior gel-forming ability to CC. Two- and three-washing cycles in conjunction with a 40°C-preincubation resulted in the highest textural properties of SC and CC, respectively. CaCl2 increased the breaking force of CC and SC mince gels up to 65 and 95% at 0.3 and 0.5% CaCl2, respectively, as compared to without CaCl2. However, it showed negative effects on surimi gels of both species. Both SC and CC are potential freshwater fish resources for mince and washed mince production with reasonable good gel-forming ability.  相似文献   

20.
Abstract –  Antipredator defences in prey species are moulded largely by predation. One general expectation is that an organism's size, shape or morphology determines the optimal set of corresponding behavioural antipredator responses. We test the hypothesis that species with similar morphology and ecology exhibit similar antipredator responses by quantifying and comparing avoidance and escape responses of two similar species, leatherside chub and redside shiner. We also examine how antipredator responses of these two species translate into mortality using experimental stream enclosures. In the presence of brown trout, redside shiner increased activity level, responded to a simulated attack sooner, quicker and had a more manoeuvrable escape than leatherside chub. Predation by brown trout decreased survival of both species, but caused higher levels of mortality in leatherside chub compared with redside shiner. Similar morphology and ecology of these two prey species does not correspond to similarity in avoidance and escape responses, and this difference has consequences for the long-term survival of these species in the presence of introduced brown trout.  相似文献   

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