活鱼近距离转运称重计量系统设计及应用

装运、称重是水产品交易过程中一个重要环节,设计了活鱼近距离转运称重计量系统,分析和叙述了系统总体结构设计和工作原理。该系统由电动提升装置、气动装卸装置和自动称重计量装置、控制装置组成。控制部分以可编程逻辑控制器(PLC)为核心,驱动电动卷扬机和气缸分别进行活鱼提升和装卸,并依靠鱼体自重沿倾斜主滑槽输送至岸上运输车,转运至目的地。软件部分基于LabVIEW可视化平台设计了转运系统显示界面,界面具有系统通讯和数据存储操作等功能。系统应用效果表明,活鱼近距离转运称重计量系统单次传输量300kg,转运量2t/h ,提高了活鱼转运效率,减少了大量人力,降低了活鱼的机械损伤率,提升了渔业生产机械化水平。     

Effects of water flow velocity and fish culture on net biofouling in fish cages

The effects of water flow, fish feed and cage position on net biofouling was examined in a floating cage fish farm. Fouling of 16 mm mesh net panels suspended inside and outside net cages and exposed to different treatments were monitored weekly until net apertures were completely occluded by the fouling organisms (8 weeks). Results indicate a dramatic reduction in water flow velocity throughout the fish farm due to the cage units themselves and net biofouling. The reduced water flow (<10 cm s^?1) inside net cages promoted rapid net biofouling, while rapid water flow outside the net cages (>25 cm s^?1) kept the net fouling organisms at bay. Although fish rearing in net cages with inputs of commercial pellet feed increased sessile biofouling (222% higher than outside the net cages) and non‐sessile biofouling (570% higher), the type of fish feed used did not significantly affect biofouling development. The study recommends that the geometry of serially arranged net cages, as commonly deployed in tropical tidal estuaries, be reconfigured to improve flow through in order to minimize the impact of fouling.     

A microcomputer program for stimulating effects of physical transport processes on fish larvae

A simple microcomputer program uses Lagrangian particle tracking to simulate the fates of individual larvae subject to wind- and tide-driven advection fields and diffusion. Space/time advection patterns are provided to the program as inputs; thus, the program can use results from various hydrodynamic models. The program can simultaneously track several groups of larvae that are assigned varying attributes, including (1) body size, to allow simulation of effects of variation in growth rates; (2) spawning locations and times; (3) vertical migration behavior; and (4) settlement strategy (duration of larval period, depth conditions for settlement). The model is intended as an exploratory tool to help identify alternative hypotheses that might explain observed life history patterns and causes of inter-annual variation in recruitment rate. For English sole in the Hecate Strait, B.C., the model leads us to hypothesize that observed spawning locations have resulted from a tradeoff between places that would provide the best feeding opportunities and places that would minimize risk of advective export to unfavorable rearing habitats.     

冷水鱼循环水养殖中的低温氨氮处理技术研究

为解决冷水鱼养殖过程中养殖水体中的氨氮累积问题,根据低温生物滤器及臭氧催化氧化处理氨氮的特点,设计了冷水鱼工厂化养殖氨氮处理系统并进行了试验。试验基于以臭氧氧化为主、低温生物处理为辅的处理工艺,试验鱼为虹鳟鱼,养殖密度为23 kg/m3,试验水体约为10 m3,试验周期为7 d。结果表明,该系统能够满足冷水鱼工厂化养殖过程中有关氨氮处理的水质指标要求,处理后的养殖池进水口的水质指标总氨氮≤0．18 mg/L,硝酸盐氮氮≤29．43 mg/L,亚硝酸盐氮氮≤0．1 mg/L;养殖水体氨氮浓度监测表明,臭氧在水中残留低于0．008 mg/L,符合养殖鱼类对水体臭氧浓度的安全要求。     

Effect of gelatinized wheat and maize in diets for large Atlantic salmon (Salmo salar L.) on glycogen retention, plasma glucose and fish health

This publication reports on analytical data from a large-scale experiment, using 3360 Atlantic salmon, Salmo salar L., distributed into 12 sea cages. Salmon were grown from an average 600 g to an average 3.5 kg. Samples for analyses were taken when fish were in the range of 1.8 and 3.5 kg. Dietary changes between groups were increased starch from 24 to 230 g kg^?1 and balanced with protein. The diets were isolipic. All salmon showed small stores of glycogen in all analysed organs, and only in heart, gills and kidney of large fish (3.5 kg) were the levels correlated with dietary starch. Minor differences between groups were found in liver NADPH production, but with substantially decreased NADPH production per g protein as the fish grew from 1.8 to 3.5 kg, indicating that increasing dietary starch did not lead to induction of liver hexokinase, and that the activity of this enzyme may decline as fish size increases. An increase in plasma glucose concentrations was found as dietary starch increased, but all levels were moderate and ranged within reference values. Plasma total protein concentrations did not, however, vary according to decreased dietary protein, but increased substantially in all groups as the fish grew from 1.8 to 3.5 kg. Dietary treatments had no influence on haematological parameters, except for decreased haemoglobin concentrations as dietary starch increased in large fish (3.5 kg). No impared liver function was detected, evaluated by activities of ASAT, ALAT and LDH, and by histological analyses. Low serum lysozyme activities were recorded in all groups, and were not correlated with plasma glucose or liver glycogen concentrations.     

Effect of handling and fish size on secondary changes in carbohydrate metabolism in Atlantic salmon, Salmo salar L.

Two size groups (0.5 and 3 kg) of Atlantic salmon, Salmo salar L., were stressed by netting and transport from sea cages into land-based tanks. Handling lasted for 1 h. Before onset of stress, basal concentrations of haematocrit and haemoglobin, plasma cortisol and glucose, and liver and muscle glycogen were measured. All levels were within ranges reported for salmon. After handling and at chosen time intervals during recovery, samples were taken to judge the impact of handling and whether secondary changes in carbohydrate metabolism were related of fish size. A low cortisol peak indicated a mild stress reaction after handling independent to fish size. Plasma glucose peaked as cortisol declined, and returned to basal levels within 48 h. Liver glycogen seemed to be the main source of plasma glucose. No changes were measured in muscle glycogen concentrations. The results indicate a high tolerance to handling stress in Atlantic salmon independent of fish size.     

A delay-differential model for representing small pelagic fish stock dynamics and its application for assessing alternative management strategies under environmental uncertainty

We present a novel adaptation of the classic discrete delay-difference model, a continuous delay-differential model (cDDM), which can adequately represent population dynamics of stocks that turn over rapidly and continuously over time (e.g., small pelagic fish, small tunas, and shrimps). We used the Northern-Central Peruvian anchoveta stock (Engraulis ringens, Engraulidae) as a case study for implementing the cDDM and conducted a management strategy evaluation (MSE) through stochastic optimization in policy space (SOPS). Our results showed that cDDM integrated with SOPS efficiently searches optimum and near-optimum harvest control rules (HCR) and is an alternative to pre-setting arbitrary HCRs as in traditional MSE. The cDDM showed comparable stock biomass and recruitment estimate reconstructions to more complex stock assessment models described for anchoveta. We concluded that the anchoveta stock is sustainably managed and is an example of adaptive fisheries management under high ocean-climate variability and uncertainty. Contrary to fishery textbooks, the anchoveta's collapse was not entirely due to the 1972 El Niño (EN) but a recruitment failure preceding EN. Our reconstructions revealed that low recruitment (or recruitment failure) could still occur at high stock biomass. Anchoveta's stock biomass is larger than pre-collapse, likely due to favourable environmental conditions (a cooling trend) and management, despite more frequent and stronger EN events. SOPS quickly revealed that harvest strategies with large base biomass (>5 mmt) lead to higher interannual stock variability and would not produce substantial increases in long-term yield. Alternative HCRs with lower base biomass, while adjusting for productivity regimes, have similar long-term yields without affecting the long-term average stock.     

东海区夏、秋季大型水母分布区渔业资源特征分析

本文根据1999～2004年的夏季和秋季东海区大型水母和渔业资源的状况,分析了大型水母分布区内的渔业资源特征。结果表明大型水母夏季主要分布于30°30′～33°00′N间,秋季主要分布于32°00′N以北海域,并呈现由夏季到秋季逐渐往北转移的趋势;2003年是大型水母数量最高的年份,该年水母主要分布区内的渔业资源种类数最少,CPUE最低,Margalef种类丰富度指数也最低;2003年夏季水母高发区内渔获种类的优势度也较其它年份发生了显著变化,优势种变为黄;2003年水母高发区内带鱼、小黄鱼和银鲳的当龄鱼较少,银鲳的肥满度增加,小黄鱼的肥满度降低,而带鱼的肥满度未发生显著变化。本文对水母高发区内渔业资源变化的原因进行了初步解释,并对水母的防治措施提出了初步的建议。     

Effect of sorbitol on moisture transportation and textural change of fish and squid meats during curing and drying processes

SUMMARY: Atka mackerel (Am) and Japanese common squid (Sq) meats were cured in 0.5–1.5 M sorbitol solutions (pH 7.0) and dried at 30°C (relative humidity, 60%), and the effect of sorbitol on the moisture transportation and textural change during the curing and drying processes was investigated. With an increase in sorbitol permeated through samples, the moisture contents decreased by 52% (Am) and 42% (Sq) by curing in 1.5 M sorbitol solution. When the cured meats were dried, slow moisture vaporization occurred at the initial drying period, and the critical moisture content significantly decreased with an increase in the sorbitol content of the cured meats. Further, the hardening of the dried products was effectively suppressed by sorbitol curing. These effects of sorbitol would contribute to the reduction of drying time and particularly the elimination of the excess hardening of dried fish products.     

Effect of fish feed processing conditions on digestive protease activities, free amino acid pools, feed conversion efficiency and growth in Atlantic salmon (Salmo salar L.)

The responses of the digestive proteases trypsin and chymotrypsin and protein metabolism to differences in feed protein quality were investigated in Atlantic salmon (Salmo salar L.). Two sets of experimental feeds were produced. Each set of high and low quality feeds was provided to either 150 g or 2 kg salmon. Protein in the high quality feeds had significantly higher percentages of free (reactive) sulphydryl (SH) groups than the corresponding feeds based on low quality meals. After 90 days feeding, groups given high and low quality feeds did not differ in their specific growth rates (SGR) in either experiment. However, feed conversion efficiency (FCE) was significantly different between the high and low quality feed groups in 2 kg salmon, where the difference between the high and low feed protein qualities was larger, 10% versus 4% SH/[SH + (S–S)] in 150 g salmon. Higher FCE was preceded by significantly higher trypsin and chymotrypsin specific activities on day 60. SGR, in general, changed after the first month and was stable during the last 2 months in both experiments. Concurrently, both trypsin (T) and chymotrypsin (C) decreased with an increased activity ratio of trypsin to chymotrypsin (T/C ratio), and resulting in significantly lower T/C ratio on day 90 in salmon feeding on high quality feeds in both sizes of fish. Differences in FCE were associated with significant differences in levels of total free amino acids (TFAA) in the plasma and the white muscle, as well as in the ratio of essential to non‐essential free amino acids (EAA/NEAA ratio), free hydroxyproline, and RNA in the white muscle. Interestingly, after 3 days starvation (day 93), 5–7 h postprandial EAA/NEAA ratio in the plasma was significantly lower in the high quality diet groups in both experiments. Trypsin specific activity inversely correlated with muscle TFAA levels in 2 kg salmon, concurrent with higher muscle levels of RNA, lower free hydroxyproline and higher FCE in fish fed higher quality diets.     

Effect of protein hydrolysate from Antarctic krill meat on the state of water and denaturation by dehydration of lizard fish myofibrils

ABSTRACT: To utilize Antarctic krill as functional food, protein hydrolysates were prepared by enzymatic hydrolysis. Their effects on the state of water in myofibrils of lizard fish and dehydration-induced denaturation were compared with those from two species of shrimp, glucose, and sodium glutamate. Peptides are major components in hydrolysates, occupying approximately 85–93% of the total materials. The Antarctic krill protein hydrolysates stabilized the bonding of water molecules, leading to suppressed denaturation of myofibrils during the dehydration process. Similar effects were observed for shrimp protein hydrolysates. The effect of the hydrolysate was less than that by glucose and sodium glutamate.     

Effect of dietary replacement of fish meal by soybean protein concentrate on growth performance and phosphorus discharging of juvenile black sea bream,Acanthopagrus schlegelii

The 8‐week experiment was conducted to evaluate the effects of partial replacement of fish meal (FM) with soybean protein concentrate (SPC) on juvenile black sea bream, Acanthopagrus schlegelii (10.70 ± 0.04 g). Diets were formulated to replace FM protein by SPC at 0, 8, 16, 24, 32 or 40% (designated as T1, T2, T3, T4, T5 and T6, respectively). Diets except T1 were supplemented with phytase at 2000 phytase activity U kg^?1. The results showed that survival rate, growth performance and feed utilization were not significantly affected by increasing dietary SPC. Fish fed diet T3 had higher feed intake compared to those fed T1, T2 and T5 diets. Whole body compositions of black sea bream were significantly influenced by SPC replacing FM except for protein, ash and phosphorus content. Condition factor of fish was significantly lower in T2 than that of fish in T3 group. Apparent digestibility coefficients (ADCs) of dry matter was higher in fish fed T6 diet than those of fish fed T1 and T2 diets, ADCs of phosphorus increased with dietary SPC level up to T3 and then decreased. The results obtained in this study indicate that FM protein could be effectively replaced by SPC protein with phytase in diet of black sea bream.     

Effect of shrimp head protein hydrolysates on the state of water and denaturation of fish myofibrils during dehydration

ABSTRACT:   To utilize fisheries waste products as food materials with functional properties, shrimp head protein hydrolysates (SHPH) from three species of shrimp, that is, Northern pink shrimp ( Pandalus eous ), Endeavour shrimp ( Metapenaeus endeavouri ) and Black tiger shrimp ( Penaeus monodon ), were produced by enzymatic hydrolysis using endopeptidase derived from Bacillus subtilis and exopeptidase derived from Aspergillus oryzae at a level of 0.1% (w/w). SHPH were rich in protein (90–91%) and amino acids (71–84%) but little fat (0.01–0.02%). The average molecular weight of SHPH was 300–1400. The effect of 5% SHPH (dry basis) addition on the state of water and denaturation of lizard fish myofibrils (Mf) during the dehydration process was evaluated by the desorption isotherm and the Ca-ATPase activity, and compared with the effect of sodium glutamate (Na-Glu). SHPH decreased the water activity and the Ca-ATPase inactivation, and increased monolayer sorbed water and multilayer sorbed water of Mf, although these effects of SHPH were smaller than those of Na-Glu. These findings suggest that the SHPH suppressed dehydration-induced denaturation of myofibrillar protein by stabilizing the hydrated water surrounding myofibrils.     

Effect of fish density and number of infectious fish on the survival of rainbow trout fry, Oncorhynchus mykiss (Walbaum), during epidemics of infectious pancreatic necrosis

Two laboratory studies compared the effect of fish density and number of infectious fish on characteristics of survival of rainbow trout fry during controlled epidemics of infectious pancreatic necrosis (IPN). Analyses of hazard functions and survivor functions were used to determine whether peak death rate, time at which the peak death rate occurred and probability of survival to the end of the experiment were associated with fish density and number of infectious fish added (i.e. pathogen concentration). When number of infectious fish was low and fish density increased, the peak death rate increased, time of the peak death rate decreased and the probability of survival to the end of the experiment decreased. When number of infectious fish was high, the effect of density diminished. Loglogistic regression of survival data revealed that fish density, number of infectious fish and interaction between these two variables significantly affected time to death from IPN (P < 0.01).     

Effect of density on survival,physiological parameters and water quality during pirarucu transportation in open system

The loading density of pirarucu Arapaima gigas transported for 6 hr in open system was assessed on survival, physiological parameters (blood hematocrit, cortisol, lactate and glucose concentrations) and water quality (temperature, pH, ammonia, dissolved oxygen and carbon dioxide). No mortality was observed after fish transportation at 80, 120 and 160 kg/m³, although ammonia and carbon dioxide concentrations increased and dissolved oxygen decreased. Physiological parameters were not affected by loading density but significant differences were observed between sampling periods (immediately before transport, immediately after transport, 24 and 96 hr after transport), except glucose. Hematocrit values increased with time, whereas lactate concentration decreased. No significant differences were observed in blood cortisol levels before and after transport, but concentration increased gradually for 96 hr after transport. According to the results, 9 kg pirarucu may be transported for up to 6 hr at a loading density of 160 kg/m³.     

Effects of fish size and water temperature on the acute toxicity of boron to Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> and red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis>

ABSTRACT:     The acute toxicities of boron were examined for Japanese flounder Paralichthys olivaceus and red sea bream Pagrus major in terms of fish size and water temperature. Japanese flounder of 0.1–70.0 g and red sea bream of 0.6–20.3 g were exposed to different concentrations of boron for 96 h at 20°C under semi-static conditions. In both fish species, the median lethal concentration (LC₅₀) for 96 h of boron increased linearly with increasing fish size, ranging from 108 to 252 mg B/L for the flounder, and from 97 to 172 mg B/L for the sea bream. The effect of water temperature on acute toxicity was examined for Japanese flounder of 0.6 and 1.5 g at 10, 15, 20 and 25°C, and for red sea bream of 0.6 and 2.4 g at 12, 15, 20 and 25°C. The toxicity of boron for the flounder increased linearly with increasing water temperature. The 96 h LC₅₀ values ranged from 299 to 108 mg B/L for the 0.6 g flounder and from 350 to 113 mg B/L for the 1.5 g flounder. A similar trend was shown for the 2.4 g red sea bream; however, the relationship for the 0.6 g red sea bream was not significant.     

Geographic influences on and the accuracy and precision of age estimates for the red bass, Lutjanus bohar (Forsskal 1775): A large tropical reef fish

The red bass is a large tropical reef fish (Lutjanidae, tropical snappers) that is harvested to varying extents throughout a widespread Indo-Pacific distribution. The aims of this study were to investigate the accuracy and precision of age estimates from transverse sections of sagittal otoliths and to assess effects on these of the geographic area of collection and otolith preparation method. Two independent validation studies suggested an approximately annual formation of annuli in otoliths, predominantly for otoliths with 4–10 annuli but also for one otolith with 29 annuli. Otolith sections produced exceptionally high annulus counts: up to 56 annuli for samples from the Great Barrier Reef (GBR), Australia; and up to 55 annuli from the Seychelles, indicating a high longevity for this species. The precision of otolith readings from the GBR (index of average percent error, IAPE = 3.21 ± 0.26 S.E.) was within commonly accepted bounds for age estimation (IAPE up to 5%) but precision of readings from the Seychelles was significantly lower (IAPE = 9.18 ± 0.47 S.E.) and outside of this “acceptable” range. Age-based biological parameters for red bass from the Seychelles should thus be applied with greater caution than those for red bass from the GBR. If basic demographic properties are assumed relatively constant across the wide geographic range sampled, however, results from the GBR could be used as more reliable preliminary data for precautionary management strategies in the Seychelles and elsewhere.