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Geriatric Veterinary Care for Fish Patients
Abstract
There is little evidence-based research and scientific literature available for providing geriatric care for fish patients. Fish can have tremendous longevity. Although the average life span for most fish species can be only a few days to weeks for the beginning hobbyist, it is becoming more common for clients to have animals for several decades with the advent and continued development of improved life-support systems, husbandry, water quality additives, and fish nutrition. This article discusses fish longevity for several popular species, addresses environmental quality issues for geriatric patients, and provides information on the most common challenges, from a veterinary perspective, to maintain fish over the years.
... The objective of environmental enrichment is often to make the enclosure resemble the natural habitat of the animals. This can be difficult with fish due to the wide range of species, combination of species kept, limited information about wild fish habitats (Williams et al. 2009), and changing habitat requirements as fish age (Weber 2010). ...
... Fish that can live for decades often survive for only a few weeks when kept by beginners (Weber 2010). ...
... Nitrates, a by-product of fish excretion, slow fish growth and reduce their resistance to disease . It is probable that many owners attribute fish deaths caused by poor water quality to illness or old age (Weber 2010 aquarium fish welfare to date, so there are no compounding effects from previous campaigns that participants could have been exposed to. ...
More than 1.5 billion fish are traded internationally each year. Fish are the most numerous type of pet and are kept in approximately 10% of Western households. Several studies indicate that most people do not consider fish welfare to be important, although scientific evidence shows that fish are behaviourally complex and feel pain.
The aim of this thesis is to develop pathways for improving the welfare of pet fish.
The welfare of captive fish is influenced by factors contributing to fish health (such as water quality, stress and behavioural needs) as well as factors contributing to the owner’s provision of care (such as knowledge, attitudes, social norms and media coverage). The relationships between these factors were explored using three methods: a survey of fish owners; an intervention using a short film to improve owner attitudes and behaviour; and the development of preference and motivational testing for determining the value of enrichment for fish.
The survey identified fish owners’ perceptions of the main welfare issues affecting pet fish and helped model the attitudes that underlie aquarist behaviour. Fish owners responding to the survey (n = 534) reported that disease and old age were the most common causes of death for their pet fish, although it is likely that many of them underestimated the role of water quality in fish health. The majority of respondents (73%) reported that they are knowledgeable about fish care and actively share and seek information about their fish. However, more than a quarter of respondents (27%) admitted that they had limited knowledge of fish care and rarely sought information or social support for their hobby. Almost all respondents provided structural enrichment such as gravel and shelters for their fish, but less knowledgeable owners were more likely to provide artificial plants than real ones.
Providing fish owners (n = 195) with a short film encouraging them to clean their aquaria weekly did increase the frequency of tank cleaning, but only if they already intended to do so. There was no measurable change in attitudes after watching the film, but using a positively framed film appeared to increase recall of the key message compared to the negatively framed film.
... Despite this considerable life span, very little has been published regarding any diseases or conditions present in these species, with the exception of some parasites [11,12]. Numerous species of fish are known to be particularly long-lived, with wild and captive species being known to live for many decades to over a century [13,14]. Environmental quality and, in the case of captive animals, husbandry practices influence longevity, with water quality having a critical influence on physiological parameters including immune function in fish [15]. ...
... Round cell, epithelial and mesenchymal tumors have all been described in fish, with ectoderm-and endodermderived epithelial tumors being the most commonly occurring and the skin being the most commonly observed site of occurrence [19,21,22]. While cutaneous fibromas are not uncommon in fish, fibrosarcomas, which are common skin tumors in domestic animals like dogs and cats, are reportedly less common in fish, having been documented in the oral cavity, operculum, and caudal peduncle of a catfish (Hemiarius dioctes), the skin of the lateral body wall of a goldfish (Carassius auratus) and a hooknose (Agonus cataphractus), and on the flank near the dorsal fin of a perch (Perca flavescens) [13,17,19,[22][23][24][25][26][27][28]. Herein, we report on surgical anaesthetic considerations and the clinicopathological features of a cutaneous fibrosarcoma in the gular region of a saddled bichir (Polypterus endlicheri endlicheri) in Trinidad and Tobago. ...
Bichirs (Polypterus spp.) have frequently been studied with regard to comparative and developmental anatomy; however, very little information has been published regarding diseases, aging changes, and medical and surgical management in these species. Neoplasia represents one such example of conditions for which a dearth of information in these species exists. There has been increasing recognition of various types of neoplasms, including cutaneous tumors, particularly in ornamental fish; some of which may be related to environmental or to infectious causes. When excision of such tumors is indicated, surgical anaesthesia is required. However, special considerations may be warranted when employing immersion anaesthesia protocols in facultative air-breathing fish that can utilise the lungs for respiration. This anatomophysiological feature of Polypterus spp. may not only influence induction and maintenance of surgical anaesthesia but may theoretically have implications for drowning. Herein, we describe the management of a case of a rapidly growing gular neoplasm in a juvenile saddled bichir and considerations for surgical anaesthesia in this “lunged” species. Induction and maintenance of surgical anaesthesia using tricaine methanesulfonate (MS-222) in this species were found to be effective at significantly lower concentrations than standard recommended doses. Histopathological analysis identified the mass as a fibrosarcoma. To the best of our knowledge, this is the first report of a cutaneous fibrosarcoma in a bichir, representing the first report of neoplasia in Polypterus spp. and the first description of surgical anaesthesia in this amphibious fish.
... Several veterinary texts on fish medicine are now available (Gratzek 1992;Brown 1993;Stoskopf 1993a;Noga 1996Noga , 2010Wildgoose 2001;Roberts 2010) most of which include chapters on anesthesia and/or surgery of fish. Major zoological medicine texts contain chapters on fish medicine, anesthesia and surgery (Harms 1999(Harms , 2003Harms 2003;Neifer 2007;Stamper 2007), and nearly every issue of The Veterinary Clinics of North America-Exotic Animal Practice includes a review article on fish medicine in line with the theme of the issue, even a recent one on geriatrics (Weber 2010). All major national veterinary continuing education meetings include lectures and often practical instructional laboratories on fish medicine, and there are several standalone fish medicine continuing education courses (Hartman et al. 2006). ...
The current role of veterinarians participating in the intracoelomic surgical implantation of electronic tags in fisheries
research projects with researchers is limited, but could be expanded. Veterinary training is broadly applicable to conducting
surgeries on any species, and there are increasing numbers of veterinarians with fish-specific experience. A few of the roles
veterinarians can play include advising on surgical instrument selection and acquisition, interfacing with Institutional Animal
Care and Use Committees, devising strategies for anesthesia, providing direction on disinfection and sterilization, complying
with regulatory requirements, providing individualized surgery instruction, and occasionally performing field surgeries. Veterinarians
and fish researchers bring different strengths and deficits to bear in a fish surgery project, and it is helpful to recognize
these for successful collaborations. Engaging veterinary consultation for electronic tag implantation surgeries in fish can
be a mutually beneficial experience for the researcher and the veterinarian, with dividends in data quality and welfare of
the research subjects.
KeywordsFish–Surgery–Telemetry–Veterinarian
Dietary sources of thiamine (vitamin B(1)) and thiamine-degrading enzymes (thiaminases) are thought to be primary factors in the development of thiamine deficiency among Great Lakes salmonines. We surveyed major forage fish species in Lake Michigan for their content of thiamine, thiamine vitamers, and thiaminase activity. Concentrations of total thiamine were similar (P <= 0.05) among most forage fishes (alewife Alosa pseudoharengus, bloater Coregonus hoyi, spottail shiner Notropis hudsonius, deepwater sculpin Myoxocephalus thompsonii, yellow perch Perca flavescens, ninespine stickleback Pungitius pungitius, and round goby Neogobius melanostomus) and slightly lower in rainbow smelt Osmerus mordax. Concentrations of total thiamine were all above the dietary requirements of coldwater fishes, suggesting the thiamine content of forage fish is not the critical factor in the development of thiamine deficiency in Lake Michigan salmonines. Thiamine pyrophosphate was the predominant form of thiamine in most species of forage fish, followed by free thiamine and thiamine monophosphate. Total thiamine was slightly greater in summer collections of alewife and rainbow smelt than in spring and fall collections, but the same was not true for bloater. Thiaminase activity varied among species and was greatest in gizzard shad Dorosoma cepedianum, spottail shiner, alewife, and rainbow smelt. Thiaminase activity in alewife varied among collection locations, season (greatest in spring), and size of the fish. Size and condition factors were positively correlated with both total thiamine and thiaminase activity in alewife. Thus, thiamine and thiaminase activity in forage fishes collected in Lake Michigan varied among species, seasons, year caught, and size (or condition). Therefore, multiple factors must be considered in the development of predictive models for the onset of thiamine deficiency in Great Lakes salmonines. Most importantly, thiaminase activity was great in alewives and rainbow smelt, suggesting that these prey fish are key causative factors of the thiamine deficiency in Great Lakes salmonines.
The relationship was examined between the occurrence of M74 syndrome (abnor-mally high yolk-sac fry mortality in the Baltic salmon) and the thiamine (B 1 vitamin) concentration in the eggs, liver and white muscle of female salmon broodfish and in the fry. Newly stripped eggs with total thiamine concentrations of ca. 0.35 mg kg –1 or lower were shown to develop into M74 offspring. M74 syndrome was not found to exist in the Teno river Atlantic salmon or in the Daugava river Baltic salmon, but was prevalent in 1994–1996 in the Finnish rivers flowing into the Gulf of Bothnia. This is thought to be a result of the low reserves of thiamine in the broodfish during maturation in these rivers. It was shown that sexual maturation of female salmon broodfish entails the transport of a large amount of thiamine to the ovaries. The total thiamine content of the liver was only a fraction of that needed in the eggs, but white muscle tissue may act as a reserve for this purpose.
Thiamine pyrophosphate, thiamine monophosphate, and thiamine were measured by reversed phase high-performance liquid chromatography in tissues of lake trout Salvelinus namaycush and alewife Alosa pseudoharengus. Mean assay sensitivity for thiamine and its phosphates was 0.012 pmol. Average recoveries of low and high doses of thiamine compounds added to tissue samples ranged from 91.4 to 104.5%. Average coefficients of variation for between assay reproducibility ranged from 4.8 to 12.8%. The predominant form of vitamin B1 was unesterified thiamine in eggs and plasma of lake trout. Thiamine pyrophosphate was the predominant form in red blood cells, liver, muscle, and kidney, The stability of thiamine forms in fish tissues was temperature and species dependent. Thiamine levels were markedly depressed in lake trout collected from Lake Ontario relative to levels in fish captured from Lake 468 at the Experimental Lakes Area in northwestern Ontario.
Captive whitetip reef sharks, Triaenodon obesus,at Sea Life Park (SLP) Hawaii, Waimanalo, Hawaii develop goitre, whereas, T. obesus at the Waikiki Aquarium (WAQ), Honolulu,Hawaii do not develop goitre. To determine theeffects of natural concentrations of iodine on thereduction of goitre, two sharks from SLP with goitrewere placed in an enclosed coastal lagoon with naturalseawater. Using ultrasound measurements the twogoitres were initially 11.4 cm and 14.6 cm in depthand after 3 months decreased to 4.7 cm and 5.7 cm. Radioimmunoassay analysis of the thyroid hormoneT3 sera concentrations were initially 0.22 ng/mland 0.33 ng/ml and increased to 1.84 ng/ml after beingplaced in the lagoon. Sera T4 were initially0.93 ng/ml and 0.99 ng/ml and increased dramaticallyto 17 ng/ml and 56 ng/ml. Over the six month samplingperiod, two resident sharks in the lagoon with normalthyroids had sera T3 concentrations from 0.89ng/ml to 1.1 ng/ml, and sera T4 concentrationsfrom 3.1 ng/ml to 7.9 ng/ml. The hypothyroidcondition in the SLP goitred-sharks is likely linkedto the low environmental iodide (
Dietary sources of thiamine (vitamin B1) and thiamine-degrading enzymes (thiaminases) are thought to be primary factors in the development of thiamine deficiency among Great Lakes salmonines. We surveyed major forage fish species in Lake Michigan for their content of thiamine, thiamine vitamers, and thiaminase activity. Concentrations of total thiamine were similar (P ≤ 0.05) among most forage fishes (alewife Alosa pseudoharengus, bloater Coregonus hoyi, spottail shiner Notropis hudsonius, deepwater sculpin Myoxocephalus thompsonii, yellow perch Perca flavescens, ninespine stickleback Pungitius pungitius, and round goby Neogobius melanostomus) and slightly lower in rainbow smelt Osmerus mordax. Concentrations of total thiamine were all above the dietary requirements of coldwater fishes, suggesting the thiamine content of forage fish is not the critical factor in the development of thiamine deficiency in Lake Michigan salmonines. Thiamine pyrophosphate was the predominant form of thiamine in most species of forage fish, followed by free thiamine and thiamine monophosphate. Total thiamine was slightly greater in summer collections of alewife and rainbow smelt than in spring and fall collections, but the same was not true for bloater. Thiaminase activity varied among species and was greatest in gizzard shad Dorosoma cepedianum, spottail shiner, alewife, and rainbow smelt. Thiaminase activity in alewife varied among collection locations, season (greatest in spring), and size of the fish. Size and condition factors were positively correlated with both total thiamine and thiaminase activity in alewife. Thus, thiamine and thiaminase activity in forage fishes collected in Lake Michigan varied among species, seasons, year caught, and size (or condition). Therefore, multiple factors must be considered in the development of predictive models for the onset of thiamine deficiency in Great Lakes salmonines. Most importantly, thiaminase activity was great in alewives and rainbow smelt, suggesting that these prey fish are key causative factors of the thiamine deficiency in Great Lakes salmonines.
Twelve thyroid glands from free-living (n = 3) and captive (n = 9) elasmobranch fishes were investigated. Histological observation of the thyroids revealed two euthyroid glands, one case of mild chronic thyroiditis, three diffuse hyperplastic goiters, three diffuse colloid goiters, and three multinodular colloid goiters. The term goiter best describes the thyroid enlargement that results from hyperplasia and hypertrophy. Although elasmobranch goiters are typically linked to low aquatic iodine concentrations, iodine deficiency alone does not explain all of the observed thyroid conditions. Diffuse hyperplastic goiters typically result from either iodine deficiency or goitrogenic release of thyroglobulin from the follicle. Colloid goiters result from fluctuating iodine concentrations or goitrogenic agents that block the release of iodine from the thyroid gland. Although nitrate is a potential goitrogenic agent in aquaria, research indicates that nitrate interferes with the uptake and retention of iodide. This interference is not directly related to iodide storage in colloid goiters. Elasmobranchs and humans appear to have similar patterns in goiter development and in the etiology of the disease.
Captive whitetip reef sharks, Triaenodon obesus, at Sea Life Park (SLP) Hawaii, Waimanalo, Hawaii develop goitre, whereas, T. obesus at the Waikiki Aquarium (WAQ), Honolulu, Hawaii do not develop goitre. To determine the effects of natural concentrations of iodine on the reduction of goitre, two sharks from SLP with goitre were placed in an enclosed coastal lagoon with natural seawater. Using ultrasound measurements the two goitres were initially 11.4 cm and 14.6 cm in depth and after 3 months decreased to 4.7 cm and 5.7 cm. Radioimmunoassay analysis of the thyroid hormone T 3 sera concentrations were initially 0.22 ng/ml and 0.33 ng/ml and increased to 1.84 ng/ml after being placed in the lagoon. Sera T 4 were initially 0.93 ng/ml and 0.99 ng/ml and increased dramatically to 17 ng/ml and 56 ng/ml. Over the six month sampling period, two resident sharks in the lagoon with normal thyroids had sera T 3 concentrations from 0.89 ng/ml to 1.1 ng/ml, and sera T 4 concentrations from 3.1 ng/ml to 7.9 ng/ml. The hypothyroid condition in the SLP goitred-sharks is likely linked to the low environmental iodide (<0.005 µM), and high nitrate (111 µM) of SLP water. The WAQ well-water facility was characterized by anoxic water with high iodide (0.60 µM), total iodine (1.90 µM), and typical nitrate (24.6 µM) concentrations of interstitial groundwater. The difference of iodide concentration of SLP and WAQ tank water (<0.005 µM versus 0.60 µM) was directly related to the hydrogeology of the well-water sources. To avoid goitre in marine aquarium systems, we recommend maintaining iodide concentrations of at least 0.15 µM.
The aim of the present study was to determine the combined effect of both stress and EFA deficiency on several biological and biochemical parameters. Fish were fed during 15 weeks two isocaloric and isoproteic diets: a control diet based on fish oil and formulated to meet the n-3 HUFA requirements for this species (1.5% of n-3 HUFA) and a deficient diet containing beef tallow and formulated to be deficient in n-3 HUFA. Each experimental diet was evaluated both at high and low stocking densities (10 and 3.2 kg m−3 of initial density, respectively).
High stocking density produced a chronic stress situation with elevation of plasma cortisol levels. It also caused a reduction in hepatosomatic index and liver lipid contents, increasing the oleic acid/n-3 HUFA ratios in the polar lipids. Fish fed the EFA deficient diet at low stocking density showed common deficiency symptoms. High stocking density in fish fed the EFA deficient diet induced a higher degree of EFA deficiency symptoms leading to mortality, liver steatosis, liver lipid deposition, reduced muscle lipid and reduced n-3 HUFA contents, which particularly affected EPA, but not DHA, suggesting a preferential retention of the latter fatty acid, specially in the phosphoglycerides fraction.
Bacterial and parasitic diseases are very common problems in pet fish. Diagnostic testing for bacterial and parasitic diseases is simple to do; many tests can be done on ambulatory visits. When logical treatment strategies are initiated and supported by diagnostic testing, a successful outcome is possible. Identification of the correct pathogens also allows an educational opportunity for discussions on prevention and biosecurity practices with clients and although fish are poikilothermic, there are some bacterial and parasitic pathogens that are zoonotic.
The objective of this study was to compare the occurrence of toxicopathic liver lesions in brown trout (Salmo trutta fario) from Tinhela River near the Jales Mine, both before implementation (2002) and after completion of the governmental mitigation program (2006). Fish were caught in April 2002 and May 2006, using an electrofishing system at four sites: S0, reference station; S1, S2 and S3 as contaminated stations. In 2002, the hepatosomatic index (HSI) was significantly higher for trout captured at the contaminated sites S2 and S3 than in S0. After the rehabilitation program, the HSI of fish sampled at the contaminated sites did not differ from the reference group. The liver of trout caught at S0 exhibited the normal parenchymal and stromal architecture described for the species and there were no pathological abnormalities. In contrast, fish sampled at S3 and S2 sites had diverse toxicopathic alterations. Specifically, livers from the two contaminated sites showed bile duct hyperplasia, often with mild epithelial dysplasia and fibrotic adventitial sleeve, foci of smaller and more basophilic hepatocytes and foci of hepatocellular necrosis; the latter conditions were frequently associated. Compared with the reference animals, increased hepatocellular vacuolization was found in livers from the polluted sites. Histopathological examination revealed differences among sampling sites in the severity and diversity of hepatic lesions clearly related to the proximity of the tailings. No pathological alterations were observed in the livers of brown trout caught in the same four areas of the Tinhela River after the mitigation program in 2006. In conclusion, our results supported that drainage from the abandoned Jales Mine had deleterious toxicological effects in brown trout. Our data suggested that the governmental mitigation program may have reduced the impact of Jales tailings.
Anesthesia, diagnostic imaging, and surgery of fish have become routine parts of aquatic animal medicine. Anesthesia may be required for simple clinical procedures, diagnostic testing, or more involved surgery. Diagnostic modalities, including radiology, ultrasonography, and endoscopy, can be readily applied to fish and may provide valuable information. Despite some unique challenges, surgery can be performed in fish using basic surgical skills and principles and should be considered as a valid treatment option.
Parasitic diseases are common in fish. Diagnosis can be made through gill biopsy, skin cytology, fecal examination, or necropsy. Common parasites include protozoa, helminths, and crustaceans. Determining the cause of death in a fish is important for maintaining the health of other fish in the same environment. Due to rapid autolysis, fish necropsies should be performed promptly after death. Samples should be preserved in 10% neutral buffered formalin. Squash preparations, tissue imprints, microbiology, and virology are also useful in obtaining a diagnosis.
The thyroid glands of coho salmon collected at different stages of their anadromous migration exhibited progressive and extensive hyperplasia and hypertrophy. The incidence of overt nodule formation rose from 5% in fish collected in August to 24% in fish collected in October. The histological picture of the goiters was similar to that found in thiourea-treated teleosts and thiouracil-treated mammals. There was a concomitant, significant decrease in serum thyroxine and triiodothyronine values between September and October (thyroxine, 1.0+/-0.3 mug/100 ml and 0.4 mug/100 ml in September and October, respectively; triiodothyronine, 400.3+/-51.6 ng/100 ml and 80.2 ng/100 ml in September and October, respectively) and marked hypertrophy and hyperplasia of thyrotrophs. These data indicate a progressive hypothyroid condition which, although it may be linked to iodide deficiency, may well be enhanced by other environmental factors. The evidence for involvement of other factors is discussed.
A female, sunset, thick-lipped gourami (Colisa labiosa) that weighed 8 g and was 5.4 cm from the snout to the end of the vertebral column was examined because of a 5-mm-diameter, midventrally located mass that had developed suddenly 1 month earlier. Cytologic examination of a sample obtained by use of fine-needle aspiration, survey radiography, positive-contrast radiography of the gastrointestinal tract, and Doppler ultrasonography were performed to evaluate the mass. These procedures were not able to provide a definitive diagnosis, but did facilitate surgical planning. The mass was excised, and the abdominal musculature was repaired, using microsurgical techniques. Redevelopment of the mass was not detected during the 5-month period after surgery. Histologic evaluation of the mass revealed an organized hematoma of undetermined cause. Successful management of this gourami illustrated that size should not be a deterrent to diagnostic evaluation and surgical intervention in diminutive fish.
Natural populations of guppies can be found with different communities of predators. We have contrasted the early life history of guppies from high and low predation localities. Life history theory predicts that such differences in mortality pattern will select for evolutionary changes in the guppy's life history. Specifically, guppies in high-predation localities are predicted to mature at an earlier age and devote more of their resources to reproduction. We have demonstrated the predicted differences in life history patterns with experiments and observations on guppies from each type of locality. We have also selected for the predicted changes in the life history by manipulating mortality patterns in natural populations. Theories for the evolution of senescence predict that these same mortality patterns will also select for changes in the rate of aging. Specifically, guppies from high-predation localities should have higher rates of aging than their counterparts from low-predation localities. Experiments that select for changes in the early life history should also select for changes in the rate of aging. The existing work on guppies, therefore, presents the opportunity to use them as a new experimental system for studying the evolutionary biology of aging. Finally, I present preliminary results from a pilot study of aging in guppies. This study differs from the earlier work by Comfort because these fish have been reproductively active since they attained maturity; Comfort's fish were maintained as virgins throughout their lives. This study makes two important points. First, age-specific changes in reproductive performance represent as important an index of aging as mortality rates. Second, the rate of aging may be far more rapid in reproductively active individuals.
An undifferentiated abdominal sarcoma was removed surgically from a koi carp. The diagnostic procedures, including radiography and computed tomography, and the procedures for general anaesthesia and the surgical approach for a celiotomy in a fish are described. The gross and microscopic appearance of the tumour is described and illustrated.
Age determination and validation studies on deep-water marine fishes indicate they are difficult to age and often long-lived. Techniques for the determination of age in individual fish includes growth-zone analysis of vertebral centra, fin rays and spines, other skeletal structures, and otoliths (there are three sets of otoliths in most bony fish semicircular canals, each of which is made of calcium carbonate). Most have regular increments deposited as the fish (and its semicircular canals) grows. The most commonly used otolith for age determination is the largest one called the sagitta. Age validation techniques include: (1) tag-recapture, often combined with oxytetracycline injection and analysis in growth-zones of bone upon recapture; (2) analysis of growth-zones over time; and (3) radiometric approaches utilizing a known radioactive decay series as an independent chronometer in otoliths from bony fishes. We briefly summarize previous studies using these three validation approaches and present results from several of our radiometric studies on deep-water, bony fishes recently subjected to expanding fisheries. Radiometric age validation results are presented for four species of scorpaenid fishes (the bank, Sebastes rufus, and bocaccio, S. paucispinis, rockfishes, and two thornyhead species, Sebastolobus altivelis and S. alascanus). In addition, our analysis of scorpaenids indicates that longevity increases exponentially with maximum depth of occurrence. The reason that the deep-water forms of scorpaenid fishes are long-lived is uncertain. Their longevity, however, may be related to altered physiological processes relative to environmental parameters like low temperature, high pressures, low light levels, low oxygen, and poor food resources.
Cataract was diagnosed in Atlantic salmon (Salmo salar L) in sea water after a period of elevated surface water temperature with simultaneous rapid fluctuation in water temperature measured at 15m depth. The affected fish were from four different hatcheries and had been released the preceding spring. Fish from each hatchery were kept in four different nets, and all nets were affected, although not to the same extent. A possible relationship between cataract and fluctuation in water temperatures is discussed.
Observations at a single study site over a period of 14 years supplied evidence of long term residence at specific locations by six individuals representing five species. A single anemonefish (Amphiprion clarkii) was observed over a period of 11 years and was estimated to be at least 13 years old when it disappeared. Other individuals disappeared at the following estimated ages: Centropyge tibicen (two individuals) = six years; Lactoria diaphana = eight years; Dendrochirus zebra = five years; Plectorhynchus pictus = seven years. The A. clarkii individual was estimated to have contributed about 160,000 propagules in its lifetime, while outliving three mates as a female after nearly three years as a functional male. Evidence is presented showing that sexually functional males disappear more frequently than females, suggesting an advantage for protandry in a monogamous species.
Nitrite, an intermediate in the oxidation of ammonium to nitrate, changes hemoglobin to methemoglobin, which does not carry oxygen; nitrite may thus cause anoxia in fish and other aquatic organisms. The published literature on nitrite toxicity to fish, which consists of about 40 papers, shows that the ratio of the 24-h LC50 (concentration lethal to half of the test organisms in 24 h) to the 96-h LC50 has a median value of 2.0 and is fairly uniform across species; toxicity tests of differing duration can therefore be standardized to a common duration. In general, chronic effects are difficult to detect at concentrations below one-fifth of the 96-h LC50. Most fish concentrate nitrite in fresh water; chloride in the external environment offsets the toxicity of nitrite by competing with nitrite for uptake through the chloride cells of the gills. Bicarbonate also reduces the toxicity of nitrite, but it is less than 1% as effective as chloride. Calcium reduces the toxicity of nitrite, but much less than chloride; the effects of other metal cations have not been studied. Hydrogen ion concentration of the medium has not been shown to have a discrete effect on the toxicity of nitrite except at extreme concentrations uncharacteristic of the environments in which fish ordinarily live. Nitrite toxicity is exacerbated by low oxygen concentrations because nitrite reduces the oxygen-carrying capacity of the blood. Very small fish seem less sensitive to nitrite than fish of intermediate or large size. Present evidence suggests that salmonids are among the fishes most sensitive to nitrite. The least-sensitive species tested thus far are the largemouth bass Micropterus salmoides and bluegill Lepomis macrochirus; the largemouth bass does not concentrate nitrite.
Nitrite, an intermediate in the oxidation of ammonium to nitrate, changes hemoglobin to methemoglobin, which does not carry oxygen; nitrite may thus cause anoxia in fish and other aquatic organisms. The published literature on nitrite toxicity to fish, which consists of about 40 papers, shows that the ratio of the 24-h LC50 (concentration lethal to half of the test organisms in 24 h) to the 96-h LC50 has a median value of 2.0 and is fairly uniform across species; toxicity tests of differing duration can therefore be standardized to a common duration. In general, chronic effects are difficult to detect at concentrations below one-fifth of the 96-h LC50. Most fish concentrate nitrite in fresh water; chloride in the external environment offsets the toxicity of nitrite by competing with nitrite for uptake through the chloride cells of the gills. The strength of the chloride effect is greatest for the least-sensitive species and smallest for the most-sensitive species. The addition of 1 mg/L chloride increases the 96-h LC50 by 0.29 to 2.0 mg/L nitrite-N, depending on the species. Bicarbonate also reduces the toxicity of nitrite, but it is less than 1% as effective as chloride. Calcium reduces the toxicity of nitrite, but much less than chloride; the effects of other metal cations have not been studied. Hydrogen ion concentration of the medium has not been shown to have a discrete effect on the toxicity of nitrite except at extreme concentrations uncharacteristic of the environments in which fish ordinarily live. Nitrite toxicity is exacerbated by low oxygen concentrations because nitrite reduces the oxygen-carrying capacity of the blood. The effects of temperature have not been adequately studied. Very small fish seem less sensitive to nitrite than fish of intermediate or large size. Present evidence suggests that salmonids are among the fishes most sensitive to nitrite; channel catfish Ictalurus punctatus, blue tilapia Tilapia aurea, logperch Percina caprodes, and brook stickleback Culaea inconstans are equally sensitive or slightly less sensitive. The fathead minnow Pimephales promelas, other cyprinids, catostomids, the mottled sculpin Cottus bairdi, and the black bullhead Ictalurus melas are considerably less sensitive. The least-sensitive species tested thus far are the largemouth bass Micropterus salmoides and bluegill Lepomis macrochirus; the largemouth bass does not concentrate nitrite.
Few estimates of natural mortality have been reported for coral reef fishes, yet this information is essential for predicting the effects of recruitment fluctuations on adult populations. In this study, mortality of adult (10 species) and juvenile (11 species) labrid fishes resident on ten isolated patch reefs in One Tree Lagoon, southern Great Barrier Reef, was estimated by visual censuses covering 30 mo, from November 1981 to April 1984. Numbers of adults of all species declined linearly over this period. Mortality rates differed significantly among species, ranging from 4.9 to 69.5% per annum. Average life-span for fishes that had survived the first year of life varied from 1.6 to 11.5 yr, depending on species. Average juvenile mortality varied among species from 25 to 91.8% per annum and was highest for abundant schooling species. Different cohorts of the same species also experienced significantly different rates of mortality. No clear relationship emerged between the number of new recruits and the number of fishes surviving to one year of age. The influence of recruitment fluctuations on adult populations of labrid fishes may be difficult to predict.
Excess nitrate in aquaculture has traditionally been reduced by water exchange. Current trends in environmental regulation, however, are limiting the amount of water which may be consumed or discharged, reducing the ability to use large influxes of water to remediate excess nitrate. This will create significant challenges for the aquaculture community, as the etiology, effects and tolerable thresholds of nitrate are relatively unknown in fishes as compared to ammonia and nitrite. Three 96-h LC50 tests were conducted using 6.9 ± 0.31 g, 66.9 ± 3.4 g, and 673.8 ± 18.6 g Acipenser baeri, to determine baseline information regarding the sensitivity of this species to elevated nitrate as compared to other species, and determine if sensitivities are mediated by size. The 96-h LC50 results for nitrate-N for 6.9 ± 0.31 g, 66.9 ± 3.4 g and 673.8 ± 18.6 g fish were 1028 mg/l, 601 mg/l and 397 mg/l, respectively, indicating an increased susceptibility to nitrate with increasing size. Predictions of susceptibilities for larger animals based on linear extrapolation of the current data is also discussed. These findings reveal that nitrate may be a considerable concern for Siberian sturgeon reared in recirculating systems with limited water exchange.
Steatosis is a common feature of many liver diseases, namely non-alcoholic steatohepatitis (NASH) and hepatitis C virus (HCV) infection, but the pathogenic mechanisms differ. Insulin resistance (IR), a key feature of metabolic syndrome, is crucial for NASH development, associated with many underlying genetically determined or acquired mitochondrial and metabolic defects and culminates to inflammation and progression to fibrosis. This may have potential implications for new drug therapy. In HCV-related disease, steatosis impacts both fibrosis progression and response to treatment. Steatosis in HCV-related disease relates to both viral factors (HCV genotype 3), and host factors (alcohol consumption, overweight, hyperlipidemia, diabetes). Among others, IR is a recognized factor. Hepatic steatosis is reported to be associated with disturbance in the signaling cascade of interferon and downregulation of its receptors. Thus, hepatic steatosis should not be considered a benign feature, but rather a silent killer.
In a comparison of livers in fish (Sparus auratus and Dicentrarchus labrax) feeding on natural sources of food with livers of artificially fed animals, a much higher C18:1/C22:6 ratio was observed in the latter. Staining livers with oil red O showed extensive steatosis in artificially fed fish, but not in those naturally fed. Juvenile artificially fed fish showed a more extensive steatosis and a higher mortality rate. In steatotic fish fed a natural diet for 2 months, the liver exhibited extensive regeneration and only a few steatotic areas remained. Marine teleosts do not appear to have a proliferative response of peroxisomes and this is likely to contribute to liver lipid accumulation and subsequent steatosis. It is suggested that an excess of C18:1 (or other mono-unsaturated fatty acids), coupled with a lack of adaptive peroxisomal proliferation, is the primary cause of lipid droplet formation leading to hepatic steatosis.
The objectives of this study were to examine the relationship between thiamine concentrations in unfertilized eggs and yolksac individuals of lake trout (Salvelinus namaycush), along with any associated histopathological changes in the tissues of alevins at the hatching stage. We address these questions in a lake trout population from different spawning grounds of Lake Michigan (North and South), known for compromised survival due to early mortality syndrome (EMS). However, a dichotomous forage base of lake trout spawning stocks, with a dietary thiaminase-rich alewife in the North, and dietary low-thiaminase round goby in the South, provides the basis for the assumption that different diets may lead to differences in severity of EMS between different stocks. Lake trout eggs of 18 females were collected and fertilized individually with the sperm of several males. The eggs, eyed embryos and newly-hatched alevins were sampled to examine thiamine utilization during embryogenesis. Progenies of females with low (< 0.73 nmol/g) and high (> 0.85 nmol/g) levels of thiamine were chosen for histological studies. The obtained results showed that total thiamine levels in the body and yolk of eyed embryos and alevins at hatching were influenced by thiamine levels of unfertilized eggs and it decreased during embryogenesis (to 51% in eyed embryos and 28% in newly-hatched alevins in comparison to unfertilized eggs). The survival of lake trout until hatching stage does not correlate with the thiamine level, however it was affected by collection site and was significantly higher in fish from the South site (Julian's Reef). At the hatching stage, no pathological changes were observed in the brain, olfactory lobe, retina or liver in embryos regardless of thiamine concentrations in unfertilized eggs. It has been concluded that an enhanced thiamine requirement for the fast muscle mass growth near the swim-up stage is responsible for overt and histopathological signs of EMS. Current study confirms earlier findings that lake trout suffering from EMS can be successfully treated by immersion in thiamine solution as late as at the swim-up stage.
Fish patients with cardiovascular disorders present a challenge in terms of diagnostic evaluation and therapeutic options. Veterinarians can approach these cases in fish using methods similar to those employed for other companion animals. Clinicians who evaluate and treat fish in private, aquarium, zoologic, or aquaculture settings need to rely on sound clinical judgment after thorough historical and physical evaluation. Pharmacokinetic data and treatments specific to cardiovascular disease in fish are limited; thus, drug types and dosages used in fish are largely empiric. Fish cardiovascular anatomy, physiology, diagnostic evaluation, monitoring, common diseases, cardiac pathologic conditions, formulary options, and comprehensive references are presented with the goal of providing fish veterinarians with clinically relevant tools.
The occurrence of cataract in fresh‐water fish has recently been the cause for increasing concern amongst anglers who have been catching a steadily falling number of fish in several regions. It has been known for over 100 years that certain fish may become infested with a trematode (or fluke) which has a remarkable predilection for the lens. The life cycle begins in the intestine of the seagull where the adult trematode produces ova which are excreted on to the waters of reservoirs and lakes. The ova hatch out into miracidia which in turn invade water snails to form a sporocystic stage. Cercariae emerge from the snail and swim free to burrow into the body of a fish and find their way to the crystalline lens. The cycle is completed by the consumption of the fish by the gull in which the adult trematode once more develops. The purpose of this communication is to demonstrate the histological changes produced in the lens by the trematode.
Résumé— —L'augmentation de l'incidence de la cataracte du Poisson d'eau douce a été récemment la cause de l'inquiétude croissante des pécheurs qui prennent une quantité sans cesse diminuée de Poisson dam différentes régions. Il est connu depuis plus de cent ans que certains poissons peuvent être infectés par les trématodes (ou douves) qui se logent avec une nette prédilection dans le cristallin. Le biocycle débute dam l'intestin de la mouette ou le trématode adulte pond des oeufs qui sont excrétés dans les eau des réservoirs et des lacs. Les oeufs donnent naissance am miracidies qui à leur tour envahissent les escargots d'eau et s'y transforment en sporocystes. La cercaire se libère de l'escargot et nage librement pour se loger dans le corps d'un Poisson et se frayer un chemim jusqu'au cristallin. Le cycle est achevé par l'ingestion du Poisson par la mouette chez laquelle le trématode adulte continue à se développer. Le but de cet article est de décrire les lésions histologiques du cristallin produites par le trématode.
Zusammenfassung— —Das Auftreten von Katarakten bei Süsswasserfischen gab vor kurzem Anlass für steigende Besorgnis unter Anglern, die in mehreren Gebieten nur eine ständig abnehmende Zahl von Fischen fingen. Es ist seit über 100 Jahren bekannt, dass bestimmte Fische von Trematoden (Saugwürmer) befallen werden können, die eine merkliche Bevorzugung der Augenlinse zeigen. Der Lebenszyklus beginnt im Darm der Seemöwe, wo die envachsenen Trematoden Eier legen, die auf Wasserflächen von Staubecken und Seen ausgeschieden werden. Aus den Eiern gehen Mirazidien hervor, die ihrerseits Wasserschnecken befallen und dort ein sporozystisches Stadium bilden. Aus den Schnecken gehen dann Zerkarien hervor, die frei umherschwimmen und nach dem Eindringen in den Körper eines Fisches den Weg in die Augenlinse finden. Der Zyklus wird dadurch gesch‐lossen, dass die Möwe den Fisch frisst und dass sich in dem Vogel abermals die erwachsenen Trematoden entwickeln. Der Zweck dieser Mitteilung besteht in der Beschreibung der histologischen Veranderungen, die von den Trematoden in der Linse hervorgerufen werden.
In vitro studies have shown that rifampicin is an effective antibiotic for mycobacteria infections. Two species of tropical fish, the Firemouth Cichild Cichlasoma meeki and the Congo Tetra Phenacogrammus interruptus, were used to determine whether oral application of rifampicin might serve as an effective treatment for mycobacteriosis in tropical fish. Fish of the two species were infected with M. marinum under controlled conditions. Six or twelve weeks after infection, treatment was begun with medicated fish food containing rifampicin in combination with tetracyclin. Histological examination of epithelial cell granuloma in the anterior and posterior kidneys, as well as in liver and spleen, showed that antibiotic treatment could somewhat reduce the intensity of, but could not successfully eliminate infection. In addition, after treatment, acid-resistant rods could still be isolated from histological samples and M. marinum could be cultured from organ samples.
Fatty acids in fish can arise from two sources: synthesis de novo from non-lipid carbon sources within the animal, or directly from dietary lipid. Acetyl-CoA derived mainly from protein can be converted to saturated fatty acids via the combined action of acetyl-CoA carboxylase and fatty acid synthetase. The actual rate of fatty acid synthesis de novo is inversely related to the level of lipid in the diet. Freshwater fish can desaturate endogenously-synthesized fatty acids to monounsaturated fatty acids via a delta 9 desaturase but lack the necessary enzymes for complete de novo synthesis of polyunsaturated fatty acids which must therefore be obtained preformed from the diet. Most freshwater fish species can desaturate and elongate 18:2(n-6) and 18:3(n-3) to their C20 and C22 homologues but the pathways involved remain ill-defined. Cyclooxygenase and lipoxygenase enzymes can convert C20 polyunsaturated fatty acids to a variety of eicosanoid products. The dietary ratio of (n-3) to (n-6) polyunsaturated fatty acids influences the pattern of eicosanoids formed. The beta-oxidation of fatty acids can occur in both mitochondria and peroxisomes but mitochondrial beta-oxidation is quantitatively more important and can utilise a wide range of fatty acid substrates.
Many years ago, Alex Comfort experimentally refuted Bidder's hypothesis that fish potentially were immortal. Later morphological and physiological studies, together with observations from fish populations in the wild, revealed that fish age in a way similar to that in other vertebrates. More recently, assessments of the age of fish have been revised, and have shown that some species live much longer than was estimated. These findings, together with the difficulties of demonstrating any increase in the rate of mortality with age in the long-lived, heavily exploited populations of fish, revived Bidder's ideas. I briefly review some of the more recent literature, and conclude that there is no evidence to suggest that fish are exceptional; like other vertebrates, sooner or later they grow old and die.
There was a spontaneous outbreak of mycobacteriosis in fancy veiltail guppies, Lebistes reticulatus, raised on an ornamental fish farm in Venezuela. The clinical signs included listlessness, emaciation, spinal curvature, sunken eyes and loss of colour. Numerous acid-fast bacteria, identified as Mycobacterium species, were detected in smears from the kidneys, liver, mesentery and spleen of the fish, from fresh faecal material, and from the unborn embryos of infected gravid females. The bacteria were eradicated by the addition of kanamycin sulphate to the water at a concentration of 50 ppm, the dose being repeated on four occasions with 48 hours between each dose. Fifteen days after the treatment, none of the clinical signs described were detected in any of the treated fish. The offspring born to treated females were healthy and normal, and did not harbour acid-fast bacteria.
Surgery in fish is feasible and practical for clinical and research applications. Certain adjustments in standard surgical procedures are necessary to accommodate piscine tissue handling, skin sensitivity, aqueous respiration, anatomic variations, and patient size. General considerations for fish surgery, including anesthesia, presurgical evaluation, equipment, suture selection, and surgical site preparation, have been presented here. Procedures described include celiotomy, enucleation, pseudobranchectomy, swim bladder surgery, gonadectomy, liver and kidney biopsy techniques, telemetry device implantation, and vascular catheterization.
Model organisms like Drosophila melanogaster or Caenorhabditis elegans have revealed genes that influence senescence and the evolvability of senescence. We are interested instead in evaluating why and how senescence evolves in natural populations. To do so, we are taking the ecological geneticist's perspective of comparing natural populations that differ in factors that are predicted to influence the evolution of senescence and are evaluating whether senescence has evolved in the predicted fashion. We are also manipulating the environment to evaluate more directly the evolution of senescence. Guppies (Poecilia reticulata) are found in streams throughout the Northern Range mountains of Trinidad. Natural populations experience large differences in mortality rate as a consequence of the predators with which they co-occur. We have already shown, both with comparative studies and manipulations of the distribution of guppies and their predators, that the early life history evolves very rapidly in response to these differences in mortality. For example, high adult mortality rates select for individuals that develop more rapidly, produce their first litter of young at an earlier age, and devote more of their available resources to reproduction for the remainder of their lives. These changes were predicted by independently derived theory. Aspects of this same theory also predict how the late life history and senescence should evolve. Specifically, theory predicts that the populations that experience low mortality rates should also experience delayed senescence and longer life spans relative to those that experience high mortality rates. We are currently evaluating these predictions with representatives from two high-predation and two low-predation environments. Our presentation will focus on our pilot study, which evaluated life span, lifetime reproduction, and the patterns of aging in our laboratory populations. We will also report on the progress in our ongoing comparative studies of senescence in natural populations.