Effect of Light Intensity on Color Performance of False Clownfish,Amphiprion ocellaris Cuvier

Color performance of false clownfish, Amphiprion ocellaris Cuvier, was examined under three levels of light intensity (20–50 , 600–850 , and 2700–3500 lx) for 5 wk. The experiment was conducted in nine rectangular glass aquaria (25 × 25 × 20 cm) with three replicates. Each aquarium was stocked with 36 fish, and 3 fish were randomly sampled from each aquarium every other week. Digital images were taken weekly on each individual fish after it was anesthetized in MS‐222. The color performance in hue, saturation, and brightness was quantified using image analysis. In addition to the whole‐body analysis, each fish image was divided into ventral and dorsal parts to assess the body position‐dependent effect. Furthermore, color differences between dorsal fin, anal fin, ventral fin, and caudal fin were also quantified. The whole body was brighter at low light than at medium or at high light intensity. Irrespective of light intensity, the dorsal side was more orange but less bright than the ventral side. Brighter light strengthened overall orange color on fish fins. The dorsal fin and ventral fins appeared more orange than the anal and caudal fins regardless of light intensity and exposure duration. Similar to body color, low light also led to brighter fins, especially for caudal and dorsal fins. Our results indicate that ambient light could regulate fish color performance but could not change the pigment dominance by β‐carotene. Light intensity is unlikely to change the contrast between dorsal and ventral sides, but dim light tends to make fish body brighter, and bright light strengthens orange color on fins.     

Effects of background colour on growth performance,skin pigmentation,physiological condition and innate immune responses of goldfish,Carassius auratus

A study was carried out to investigate the effects of background colour on the growth performance, skin colour, haematology, physiological condition and non‐specific immune responses of goldfish, Carassius auratus. Goldfish were reared in tanks with four different background colours (white, black, blue and red) for 8 weeks. Fish growth performance markedly rose in white background compared with the other treatments. There was no significant difference in haematological parameters or plasma proteins concentrations between treatments. Plasma cortisol of fish reared in red background was significantly higher than that in black and white backgrounds. Plasma antiprotease and lysozyme activities were more than doubled in white and black treatments compared with the red and blue groups. The other immune parameters tested (plasma peroxidase, complement and bactericidal activities) did not significantly change between treatments. Skin carotenoid content and the intensity of fish skin colour extremely diminished in white background. This study revealed that red and blue backgrounds are chronically stressful and immunosuppressive in goldfish. White backgrounds will preferably be used for the culture of goldfish for best fish growth. However, a way to revert the colour loss of goldfish skin reared in white backgrounds remains to be investigated.     

中国南海银鲈科鱼类——新记录

2008年11月在广西北海市侨港镇码头采获银鲈科Gerreidae、银鲈属Gerres鱼类标本两尾,经鉴定为大棘银鲈Gerres macracanthus Bleeker,1854,系我国南海鱼类一新记录。其主要特征为：体长卵圆形,侧扁,体长为体高的2.2～2.3倍;体背腹缘均呈弧状隆起,体高以背鳍起点处最高。口小,能活动,伸出时略向下倾斜。体被薄圆鳞,易脱落;侧线鳞41～43枚。背鳍鳍棘部与鳍条部相连;背鳍IX-10,第2鳍棘延长呈丝状,压倒时末端伸达尾柄;臀鳍Ⅲ-7,以第3鳍棘最长;胸鳍长,末端可达臀鳍起点上方;尾鳍叉形。新鲜标本体背部银灰色,腹部银白色,体侧有7～10条青灰色横带;背鳍灰白色,第2鳍棘黑色;臀鳍、胸鳍和腹鳍淡黄色;尾鳍灰黄色,上、下叶内缘暗色,下叶外缘白色。     

Effects of tank color on the growth,stress responses,and skin color of snakeskin gourami (<Emphasis Type="Italic">Trichogaster pectoralis</Emphasis>)

The effects of tank color on the growth, stress responses, and skin color of snakeskin gourami (Trichogaster pectoralis) were investigated in this study. Fish with initial body weights of 5.03±0.00 g were reared in five experimental tank colors (white, red, green, blue, and black) for 8 weeks. Each tank color was tested in triplicate with an initial stocking density of 15 fish per tank. Fish were fed with commercial sinking pellets at 4% of the average body weight per day. Growth performance, feed utilization efficiency, stress indicators (hematocrit, blood glucose, plasma cortisol levels), and skin color parameters were investigated. The fish reared in blue tanks had a significantly higher average final body weight (9.73?±?0.14 g) and significantly lower average feed conversion ratio (3.42?±?0.12) than the fish reared in black tanks (P?<?0.05). The fish reared in black tanks exhibited higher average hematocrit (36.63?±?1.11%), blood glucose (48.33?±?1.45 mg dL^?1), and plasma cortisol (9.00?±?0.56 μg dL^?1) levels than those reared in the other tank colors. However, the blood glucose levels in only the fish reared in black tanks were significantly higher than those in the fish reared in the other tank colors. The fish skin color ranged from very pale (high skin lightness) in the white tanks to very dark (low skin lightness) in the black tanks, and 80% of the variation in skin lightness were explained by the tank lightness. The use of a blue tank resulted in normal skin color; hence, blue tanks will not affect the customer acceptance of the fish. Our study revealed that blue is the most appropriate tank color for culturing snakeskin gourami.     

美洲鲥仔稚鱼脊柱及附肢骨骼系统的早期发育

使用软骨-硬骨双染色技术,描述了美洲鲥(Alosa sapidissima)仔稚鱼(1~51日龄)脊柱、胸鳍、尾鳍、背鳍等附肢骨骼的形态发育特征。结果显示,脊柱的发育开始于10日龄仔鱼尾部的髓弓、脉弓和尾下骨的出现,16日龄髓弓和脉弓延伸形成髓棘和脉棘,19日龄脊柱出现分节的硬骨环,23日龄所有椎体形成。各附鳍支鳍骨发育顺序先后依次为胸鳍、尾鳍、背鳍、臀鳍和腹鳍。胸鳍在2日龄时出现乌喙骨,13日龄形成软骨质的胸鳍支鳍骨,19日龄仔鱼肩带和上匙骨开始骨化;尾鳍的尾下骨最早出现在5日龄,12日龄尾鳍形成2枚尾上骨、1枚尾杆骨和6枚尾下骨,19日龄仔鱼尾椎和尾鳍率先开始骨化,直至23日龄尾鳍骨骼系统钙化完全。最终背鳍和臀鳍分别形成18和22根鳍条。美洲鲥骨骼发育研究对其早期发育功能趋向、环境优化及分类鉴定有重要作用。     

A Survey of Trout Fin Erosion, Water Quality, and Rearing Conditions at State Fish Hatcheries in Utah

A total of 600 hatchery trout were examined for signs of fin erosion including rainbow trout Oncorhynchus mykiss , cutthroat trout O. clarki , brook trout Salvelinus fontinalis and brown trout Salmo trutta . A scoring system was used to evaluate erosion on all fins from 20 fish samples. Water quality and hatchery rearing variables were also determined for corresponding raceways or ponds. For rainbow trout groups ( N = 24), stepwise multiple linear regression was used to interpret the relationship between fin erosion and the other variables. These fish groups averaged between 92 and 243 mm in total length and no significant correlation was observed between length and a fin erosion index ( r = 0.045). The best-fit regression model (adjusted R² = 0.689) suggested that fin erosion was correlated with lower alkalinities, unnatural bottom substrates (concrete or steel), higher unionized ammonia levels, and higher fish densities. Despite significant variation between hatcheries, fin condition was significantly better in rainbow trout than in cutthroat trout in three of four hatcheries containing both species and the same substrate. Fin erosion in rainbow trout occurred primarily on dorsal fins, followed in order of decreasing severity, by pectoral, caudal, anal, and ventral fins.     

Fin development in stream- and hatchery-reared Atlantic salmon

To determine the effect of development and environment on fin growth, we measured fin lengths of juvenile Atlantic salmon (Salmo salar) from two hatcheries (August, October and April–May), stream-reared fish (July and October) stocked as fry into two tributaries, and smolts from the main stem of the Connecticut River (May). For stream-reared parr, there was a linear relationship between the dorsal, caudal and anal fins with fork length, while the pectoral, pelvic and adipose fins exhibited a curvilinear relationship with fork length. Parr from a high gradient stream had larger caudal fins than fish from a low gradient stream, but other fins did not differ. Regression lines for the fins of stream-reared smolts were all linear when fin length was regressed against fork length. Stream-reared parr had larger pectoral, pelvic and anal fins than smolts of similar size while dorsal and caudal fin lengths did not differ. Regression equations formulated using the fins of stream-reared parr were used to calculate the percent difference (100×observed fin length/expected) in fin lengths between stream- and hatchery-reared parr. The pelvic, adipose, caudal and anal fins of hatchery-reared parr showed no signs of degeneration by the first sampling period 7 months after hatching, whereas degeneration in the pectoral (13–20%) and dorsal (15–18%) fins was evident at this time. By the end of the study, degeneration was present in every fin except the adipose, with the pectoral (35–65%) and dorsal (32–58%) fins exhibiting the greatest amount of fin loss. All fins of hatchery-reared parr became shorter with time. There were minor differences in fin degeneration among parr from the two hatcheries, but the overall pattern of decreasing fin size was similar, indicating a common cause of fin degeneration. Comparison of stream- and hatchery-reared fish is a valuable means of determining the impact of captive environments on fin growth.     

Optimal background colour for rearing Asian seabass (Lates calcarifer)

Background colour influences the growth performance and feed utilization of various fish species. In the current study, the effects of different aquarium backgrounds (transparent, white, black, red, green and blue) on growth performance, feed utilization, digestive enzyme activities, flesh quality, carcass composition and haematological parameters were investigated in Asian seabass (Lates calcarifer). The fish (16.17 ± 0.02 g initial body weight) were distributed into eighteen glass aquaria (6 treatments × 3 replications) with the various background colours and reared for 10 weeks. At the end of the experiment, positive growth performance and feed utilization were observed in fish reared against transparent, white, black or green backgrounds, while negative effects were noted for fish reared on the remaining treatments (p < .05). Modulation of the main digestive enzymes was observed across the six treatments, indicating different strategies for utilizing nutrients by the fish. The activity ratio of trypsin to chymotrypsin was highest in the fish reared against a black background, followed by a white background. Flesh quality, in terms of protein synthesis capacity and protein turnover rate, indicated a significant improvement in the fish reared against white, black and green backgrounds, while the contents of myosin and actin were similar across the six colour treatments. Carcass composition and haematological parameters showed no negative effects in either of the preferred treatments. These findings indicate that the most suitable background colours for rearing Asian seabass are black, followed by white and green, while transparent, red or blue backgrounds are unsuitable.     

Effects of baffles and isolation on dorsal fin erosion in steelhead trout, Oncorhynchus mykiss (Walbaum)

Abstract. Dorsal fin condition was evaluated in two groups of hatchery-reared steelhead trout, Oncorhynchus mykiss (Walbaum), and compared to wild fish. Hatchery fish were reared either in nursery tanks with baffles or in isolation (1 fish/rearing space). Evaluations were conducted to determine differences in dorsal fin condition between these groups and to monitor the progression and severity of fin damage. Isolated hatchery and wild steelhead trout maintained perfect dorsal fins with characteristic white margins. Hatchery fish reared in nursery tanks with baffles experienced dorsal fin erosion that started when the fish were about 40mm total length (30 days after being on feed). This erosion continued until dorsal fin length averaged only 2·3 mm in fish 161–200 mm total length in contrast to an average dorsal fin length of 20·9mm in wild fish of the same size.     

Effects of stocking density on haematological parameters,growth and fin erosion of great sturgeon (Huso huso) juveniles

The influence of stocking density (1, 2, 4, 6 and 8 kg m^?2) was investigated on haematological parameters, growth and fin erosion of great sturgeon (Huso huso) juveniles for a period of 8 weeks. The mean weight of fish at the start of trial was 93.13±1.04 g. After 8 weeks of rearing, the mean weight was 362.4, 319.7, 267, 242.1 and 211.1 in densities 1–8 kg m^?2 respectively. The results of this study showed that growth parameters, including condition factor, weight, weight gain, feed conversion ratio, specific growth rate and body weight increase, had a statistically significant difference among treatments (P<0.05). A significant difference (P<0.05) was observed in haematocrit, but the other haematological parameters, including red blood cells, white blood cells (WBC), haemoglobin concentration, mean corpuscular haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin concentration and differential WBC count, showed no significant effect with stocking density (P>0.05). At the end of the experiment, stocking density had no significant effect on plasma cortisol and glucose concentration. The fin length (dorsal, anal, ventral, pectoral and caudal) of fish was measured to calculate the fin index. According to this index, dorsal, anal, ventral and pectoral fins showed no significant difference among treatments (P>0.05), but the erosion of the caudal fin was significantly different between fish held on 6 and 8 kg m^?2 (P<0.05). These results showed that rearing density has a major effect on the growth indices of H. huso. Unlike many other fish, great sturgeon exhibited lower stress responses to high stocking density. This indicates that they are more tolerable to rearing conditions in high stocking densities. With respect to the various effects that density causes on growth, fin erosion and physiological and haematological parameters, better understanding of these phenomena considering different levels of density could have a beneficial impact on many rearing steps of this species.     

The Physical Condition and Welfare of Five Species of Wild‐caught Wrasse Stocked under Aquaculture Conditions and when Stocked in Atlantic Salmon,Salmo salar,Production Cages

Several indices were examined to assess the physical condition of wrasse stocked on Atlantic salmon, Salmo salar, farms as cleaner fish, and included examination of eye condition, snout erosion, skin hemorrhaging, and erosion and splitting of dorsal, pectoral, anal and caudal fins. Baseline values were determined for five wrasse species: goldsinny, Ctenolabrus rupestris; rock cook, Centrolabrus exoletus; corkwing, Crenilabrus melops; cuckoo, Labrus mixtus; and ballan, Labrus bergylta, held in a farm environment for 3 mo prior to transfer to salmon farms. The caudal fin was most affected by injury. The fin erosion index (FEI) was low in all species and below 0.6. The fin splitting index (FSI) was the most prominent index and was significantly higher in the caudal fin (FSI > 2) compared with other fins (FSI < 0.5), and also significantly higher in corkwing and rock cook compared with the other wrasse species. The FEI and FSI were also calculated for a group of ballan wrasse before stocking on a seawater farm, during the first winter and upon harvesting. There were no significant differences in the scores of fin erosion and fin splitting in any of the samples, although the indices were marginally poorer in winter.     

Niacin requirement for optimum growth, feed conversion and protection of rainbow trout, Salmo gairdneri Richardson, from ultraviolet-B irradiation

Triplicate groups of 75 rainbow trout, Salmo gairdneri Richardson, (mean weight 0–76 g) were fed a semipurified diet containing added niacinamide in amounts of 0.0, 1.25, 2.5. 5, 10, 20, 40, 80 or 160 mg/kg diet (ppm), for 16 weeks to determine the amount of niacinamide needed for optimum growth, feed conversion, and prevention of dermatopathy induced by UV light. At the end of the study, fish were exposed to a 275-W sun lamp limiting in the UV-B spectrum (280–360 UV) for 20h. Trout fed no supplemental niacinamide grew significantly slower than all other fish. Growth increased with each niacinamide increment through 10ppm. but not at higher increments. Feed conversion paralleled growth response to niacinamide. Exposure to UV light induced dermal lesions in trout fed less than 10ppm niacinamide. Initially, focal white spots appeared anterior to the dorsal fin, and caudal and pectoral fins became depigmented and translucent. Later, extensive erosion in caudal and pectoral fins was accompanied by desquamation of the epidermis and underlying tissues of the caudal peduncle, head and snout. Results indicated that rainbow trout need at least 10ppm niacinamide for optimum growth, feed conversion and protection against 'sunburn’caused by UV light.     

7种观赏性剑尾鱼品种间杂交子代的体色及鳍形研究

7种观赏性剑尾鱼的自交、杂交,对其子代的体色(包括眼睛色彩)及鳍形等性状进行统计分析。试验结果表明,黑眼为显性基因控制,红眼为隐性基因控制,体色与眼睛颜色有一定的连锁关系;推测剑尾鱼体色遗传由数量性状基因参与控制;尾鳍燕尾相对于正常尾为显性,而且雄性尾鳍的燕尾和长臀鳍具有连锁性;高背鳍由显性基因控制,正常背鳍由隐性基因控制,拥有正常背鳍的个体,其基因型是隐性纯合,拥有高背鳍的个体,其基因型为杂合,初步推断显性纯合为致死基因型。     

Pigment deposition and in vitro screening of natural pigment sources for enhancing pigmentation in male Siamese fighting fish (Betta splendens Regan, 1910)

Distribution in pigment deposition was studied in male Siamese fighting fish (Betta splendens Regan, 1910) of solid Blue and solid Red phenotypes. Growths were similar, and also indicated by similar activity ratio of trypsin to chymotrypsin. Growth strategy was different at maturing stage, whereas trypsin expression decreased in solid Blue while chymotrypsin expression decreased in solid Red (P ≤ 0.05). Ranking of total pigment contents was muscle > skin > caudal fin > anal fin > dorsal fin > pelvic fin > pectoral fin. Immature fish had similar total contents and concentrations of pigments, except solid Blue had higher total contents in dorsal fin than solid Red. At maturing stage, solid Blue showed higher total pigment contents than solid Red due to higher contents in the fins. Solid blue had higher concentration in pelvic fin, while solid Red had higher in pectoral and dorsal fins. Age, phenotype and their interaction influenced pigment deposition. Determinations of pigment levels, high temperature tolerant of pigments and in vitro digestibilities of pigments, protein and carbohydrate from twenty natural sources indicated that fermented red rice was the most suitable pigment source, following with Chlorococcum sp.     

豹纹鳃棘鲈(Plectropomus leopardus)早期形态与色素变化及添加剂对其体色的影响

为研究豹纹鳃棘鲈色素变化过程以及添加剂对其产生的影响,本研究在室内工厂化养殖条件下,对豹纹鳃棘鲈的早期色素积累、转变过程进行描述,并采用螺旋藻粉和虾青素两种添加剂对其仔、稚、幼鱼的生长及体色变化的影响进行观察。结果显示,从2 d仔鱼开始,眼点色素增多,并由透明转为黑色,摄食明显;3 d仔鱼其背部鳍褶上的树枝状黑色素扩大,脊椎下方出现1列黑色素细胞丛;22 d的鱼体脊椎上方出现1排黑色素斑点,下方黑色素斑点数量减少,此时口、各鳍基部及沿脊椎两侧黄色素增加;28 d的稚鱼体表黄色素与红色素进一步增多,各鳍沿鳍条均有红色素斑点分布,鱼体呈橘红色,颜色鲜艳;30–33 d的幼鱼体表两侧布满黑色与橘红色斑点,脊椎下方斑点消失,仅在尾椎下方存有1块黑色素斑点。增色剂实验结果显示,实验15 d时,螺旋藻粉组与虾青素组全长、体重差异不显著,但均显著高于对照组(P0.05),各实验组内梯度之间差异不显著(P0.05)。30 d时,3%和6%螺旋藻粉组较对照组的体重值高,但差异不显著(P0.05),9%螺旋藻粉组显著低于对照组(P0.05);虾青素组均高于对照组,除与0.6%组差异不显著(P0.05)外,其他组均差异显著(P0.05)。0.1%实验组体重高于对照组和螺旋藻粉组,并高于组内其他梯度组。经过15 d添加虾青素的幼鱼体色红色素有明显增加,与对照组差异显著;30 d时,螺旋藻组没有达到增色效果。结果表明,螺旋藻粉对幼鱼生长初期有促进作用,随着添加浓度与养殖时间的增加其效果不明显,出现负效应;添加浓度为0.1%的虾青素可使全长、体重增长率最高并具有明显增色效果。     

锦鲤墨蝶呤还原酶基因的克隆、表达和定位分析

为探究SPR在锦鲤体色形成中的作用,实验利用RACE技术获得spr cDNA全长序列,并分析其时空表达模式,同时利用Western blot和免疫组织化学方法检测SPR蛋白在皮肤、鳍条和鳞片中的分布和表达情况。结果显示,spr cDNA全长879 bp,包含132 bp和134 bp的5′和3′非编码区,开放阅读框510 bp,编码170个氨基酸残基。氨基酸序列比对和系统进化树分析显示,锦鲤SPR具有保守的adh_short_C2结构域,与金鱼相似性高达97.7%。spr在各组织中均有表达,其中皮肤的表达量最高。spr在锦鲤个体发育的4个阶段表现为先降后升。纯红、纯白及红白3种体色锦鲤皮肤、鳞片和鳍条中spr mRNA和蛋白表达水平基本一致,在纯红锦鲤皮肤中表达量最高,红白锦鲤白色皮肤、鳞片和鳍条的表达量最低。SPR组织定位分析显示,红色锦鲤和白色锦鲤皮肤中均检测到阳性信号,其中红色皮肤阳性信号强度高于白色皮肤。研究表明,spr可能与锦鲤红/黄色素细胞的分化和形成具有一定相关性,参与了锦鲤体色的形成。     

Repeatability of fin length measurements using digital image analysis and studies of fin erosion as indicator of social interactions in Atlantic cod (Gadus morhua)

The aims of this study were to examine fin erosion caused by social interactions between Atlantic cod (Gadus morhua) juveniles, and to evaluate the repeatability of recorded fin length using digital image analysis (DIA). Fin length of 2100 juvenile Atlantic cod was analysed using DIA, during a 6 weeks experiment. The lengths of the three dorsal fins and the caudal fin were measured by three different assessors (M, K, B) three times during the experiment. Repeatability was based on a sub set of data from 42 randomly chosen fish. Assessor M measured the length of the fins of the 42 fish three times (M1, M2, M3). M1 and M2 were done on the same day, while M3 was conducted 2 weeks later. Assessor K measured two times with a 2‐year interval, and assessor B measured the fin length only once. The correlations between replicated measurements within assessor were highest for assessor M measured on the same day indicating an effect of memory. Repeatability of fin length ranged from 0.57 to 0.73 for the four fins. Social interaction with respect to fin erosion was studied using data on the four fins from all 2100 fish. ‘Relative fin length’ (fin length/total body length × 100) was calculated to assess fin erosion. Results indicated that all four fins were eroded due to social interactions, but the caudal fin was most severely eroded. In conclusion, DIA can be used to measured fin length but the method could be improved by using chromatic pictures.     

中国产细纹狮子鱼的骨学和肌肉学研究

本研究解剖了中国产细纹狮子鱼(Liparis tanakae)标本,并详细描述了该物种的骨骼系统、骨骼肌系统及相关神经,包括围眶骨、脑颅、颌骨、悬器和鳃盖骨、舌弓、鳃弓、肩带、腰带、中轴骨架和奇鳍支鳍骨、尾部骨架的10个部分骨骼,以及颊肌、脑颅与悬器-鳃盖骨间肌肉、头部腹面肌肉、鳃弓肌肉、胸鳍肌肉、腹鳍肌肉、奇鳍相关肌...     

Environmental control of skin colour in the red porgy, Pagrus pagrus

Fish display sophisticated skin chromatic properties that are of considerable ecological, physiological and behavioural importance. The aim of study was to investigate the role of important physical parameters (background colour, lighting spectrum, light intensity and water temperature) on skin colour to gain better knowledge of the environmental factors that regulate pigmentation in cultured red porgy, Pagrus pagrus . All tested physical parameters had a significant effect on skin lightness, especially in the dorsal body area; low light intensity, blue spectrum, a water temperature of 19 °C and a white background significantly increased skin lightness. This effect was mediated through changes in melanophore motility and/or skin melanin concentration. None of the examined factors affected skin hue while a significant decrease in skin entire colour index (a combination of hue and chroma) was found only in white background-adapted fish. It is concluded that all tested physical factors are important regulators of skin lightness.     

Fin erosion in a feral population of goldfish, Carassius auratus (L.), exposed to bleached kraft mill effluent

Abstract. The prevalence of acute and healed fin erosion in goldfish, Carassius auratus (L.), from the Waikato River, New Zealand, peaked in the vicinity of a pulp and paper mill which utilized a kraft pulping process in association with chlorine bleaching, and decreased down the effluent gradient. About 49% of goldfish sampled from the Kopakorahi Stream. which is part of the effluent treatment system (site 1), displayed pathological signs of fin erosion, whereas about 9% of control fish from a reference site located upstream of the official effluent discharge point were similarly affected. Fin erosion was less prevalent in male than in female goldfish, and occurred with different frequencies on different fins, the pectoral (56%) and caudal fins (33%) being most affected. Both the pectoral and caudal fins also had significantly higher proportions of healed erosion rather than acute erosion. The prevalence of acute and healed fin erosion increased significantly with increasing fish length (age). Physical deformities, predominantly in the form of eroded or otherwise malformed opercula, were found in nearly 5% of fish caught at site 1, but were not observed at the reference site. Changes in processing and bleaching technology at the pulp and paper mill in question have since been carried out, and long-term studies arc planned to monitor any subsequent improvements in fish health.