Ichthyophoniasis: An Emerging Disease of Chinook Salmon in the Yukon River

Abstract

Before 1985, Ichthyophonus was unreported among Pacific salmon Oncorhynchus spp. from the Yukon River; now it infects more than 40% of returning adult Chinook salmon O. tshawytscha. Overall infection prevalence reached about 45% in the Yukon River and about 30% in the Tanana River between 1999 and 2003. Mean infection prevalence was greater in females than males in the main-stem Yukon River during each of the 5 years of the study, but the infection prevalence in males increased each year until the difference was no longer significant. Clinical signs of ichthyophoniasis (presence of visible punctate white lesions in internal organs) were least at the mouth of the Yukon River (～10%) but increased to 29% when fish reached the middle Yukon River and was 22% at the upper Tanana River. However, clinical signs increased each year from 7% in 1999 to 27% in 2003 at the mouth of the river. As fish approached the upper reaches of the Yukon River (Canada) and the spawning areas of the Chena and Salcha rivers (Alaska), infection prevalence dropped significantly to less than 15% in females on the Yukon River and less than 10% for both sexes in the Chena and Salcha rivers, presumably because of mortality among infected prespawn fish. Age was not a factor in infection prevalence, nor was the position of fish within the run. The source of infection was not determined, but Ichthyophonus was not found in 400 Pacific herring Clupea pallasi from the Bering Sea or in 120 outmigrating juvenile Chinook salmon from two drainages in Alaska and Canada. Freshwater burbot Lota lota from the middle Yukon River were subclinically infected with Ichthyophonus, but the origin and relationship of this agent to the Chinook salmon isolate is unknown.     

Aspects of the biology of a rare redfin minnow,Barbus burchelli (Pisces,Cyprinidae), from South Africa

Burchell's redfin, Barbus burchelli is endemic to the Breede River and adjacent smaller river systems in the Cape Province. Negative human influences have led to a drastic decline in numbers of this medium-sized minnow, especially agricultural demand on the water resource and the introduction of exotic predatory fish. The breeding season is extended, from September to February, with a peak in December. The absolute fecundity of a 123 mm FL specimen was 10 678, which includes both mature and recruitment ova. Females grow larger (123 mm FL), and live longer (6 +years), than males (113 mm FL and 4 + years). 8. burchelli grow rapidly in their first year attaining a length of between 40 and 50 mm FL. Pronounced conical tubercles of sexually mature males erupt in spring, begin to show signs of wear in November and by March are worn or sloughed off. The survival of this species is dependent upon proper management of the Breede River system.     

Foraging technique and prey‐handling time in black‐necked stork (Ephippiorhynchus asiaticus)

The foraging technique and prey‐handling time of the black‐necked stork (Ephippiorhynchus asiaticus) was studied in Dudhwa National Park, India, from January 1996 to June 1997. The habitat in which the storks foraged played an important role in selecting a particular technique to procure food. Black‐necked storks mostly foraged using a tactile technique (>90%), but sometimes foraged visually. When the water level was estimated to be less than 60 cm, the storks foraged using tactile techniques. There was no difference in the feeding techniques of male and female storks. Foraging attempt rates varied between the sexes in summer (May) and during late winter (February) in 1997. The search time for prey increased when the water level was high and fish were widely distributed. Decreases in water level resulted in concentration offish in certain areas and this contributed to high fish‐catching rates by black‐necked storks. Males had a higher success rate offish capture than females. However, females captured longer fish than males. Prey‐handling time increased in both sexes as fish length increased. Fish 4–6 cm long were most frequently taken by the foraging storks.     

Communications: Blood Chemistry of Laboratory-Reared Golden Trout

Abstract

Golden trout Oncorhynchus aguabonita obtained from a wild stock as fertilized eggs were reared in the laboratory for 21 months. The laboratory-reared golden trout in our study reached sexual maturity earlier and grew more rapidly than wild golden trout do (according to the scientific literature). Male fish averaged 35.6 cm in total length and 426 g in weight, and females averaged 36.2 cm and 487 g. All golden trout were sexually mature when used for hematological analysis. The hematological profile (hematocrit, red blood cells, white blood cells, and thrombocytes) of golden trout was similar to that reported elsewhere for other trout species. Male and female golden trout did not have significantly different thrombocyte counts; however, the immobilization treatment used on the fish (anesthesia versus a blow to the head) resulted in significant treatment differences in thrombocyte numbers and interaction effect of sex in treatment for hematocrits. Gravid female golden trout had significantly higher plasma protein and calcium levels than did males. The ionic compositions of plasma (sodium, potassium, calcium, magnesium, copper, zinc, iron, and chloride) and gallbladder bile (calcium and chloride) were similar to those reported for other salmonids.     

Microscopic Evidence of the Opportunistic Reproductive Strategy and Early Sexual Maturation of the Small‐Sized Characin Knodus moenkhausii (Characidae,Pisces)

We investigated the reproductive biology of Knodus moenkhausii, an abundant small‐sized characin fish with broad occurrence in the Paraná River basin, Brazil. Specimens were collected monthly to determine fecundity, length at first maturity, reproductive period and spawning type. Gonads were macroscopically classified according to their form, size and texture in three different stages (immature, maturing or mature). Histological procedures were conducted to confirm gonadal developmental stages, and it was possible to notice that maturing females actually presented atretic oocytes, and all males that were macroscopically classified as immature, maturing and mature actually presented abundant spermatozoa in their gonads. Because of these discrepancies, a reclassification of gonadal maturations stages was needed after histological analysis, reinforcing its importance to studies on the reproduction of small characins. Reproduction occurred throughout the year though with two peaks. The length of the smallest mature individuals was 13 mm SL for males and 24 mm SL for females. Despite presenting relatively small batch fecundity, some life history traits such as early reproduction, multiple spawning throughout the year, in association with known opportunistic feeding habits, explain the high abundance of this species in locations where it occurs.     

Morphometric analysis of the spinal cord of the Sus scrofa (large white and landrace crossbreed)

The incidence of spinal cord (SC) injury in developed and undeveloped countries is alarming. The pig (Sus scrofa) has been recommended as a suitable research model for translational studies because of its morphophysiological similarities of organ systems with humans. There is a dearth of information on the SC anatomy of the large white and landrace crossbreed (LW-LC) pigs. We therefore aim to describe the gross morphology and morphometry of its SC. Twelve juvenile LW-LC pigs (six males and six females) were used. The skin and epaxial muscles were dissected to expose the vertebral column. The SC was carefully harvested by laminectomy, and 13 gross SC morphometric parameters were evaluated. Thirty-three spinal nerves were seen emanating from either side of the SC by means of dorsal and ventral spinal roots. The overall average of SC length and weight was 36.23 ± 1.01 cm and 16.60 ± 0.58 g, respectively. However, the mean SC length and weight were higher in females compared with males, with SC weight being statistically significant. A positive relationship between SC length and weight was significant for males (p = 0.0435) but not for females (p = 0.42). Likewise, the strength of the relationship between SC length and weight was significant in males (r = 0.82) but not significant in females (r = 0.41). Baseline data for the morphometric features of the spinal cord in the LW-LC pigs were generated, which will contribute to the knowledge of this species anatomy and useful information on regional anaesthesia that should further strengthen the drive in adopting the pig as a suitable research model for biomedical research.     

Ocular parameters in a captive colony of fruit bats

Objectives To establish normal reference ranges of ocular parameters including phenol read thread, palpebral fissure length, horizontal and vertical corneal diameter, upright and hanging intraocular pressure (IOP) and to report ophthalmic examination findings of the anterior segment and lens, in a population of captive fruit bats. Animals studied Eyes of 30 bats of three species were included in this study: 10 (5 males, 5 females) Malayan Flying Foxes (Pteropus vampyrus), 10 (5 males, 5 females) Little Golden‐mantled Flying Foxes (Pteropus pumilus), and 10 (4 males, 6 females) Island Flying Foxes (Pteropus hypomelanus). Results The most common ophthalmic examination findings included iris‐iris persistent pupillary membranes (83%), nuclear sclerosis (56.7%), prominent arterial circle (40%), iridal hyperpigmented foci (30%), pupillary margin cysts (27%), and third eyelid defects (20%). The mean, among all species for: phenol red thread was 20.23 ± 1.28 mm/15 s both eyes (OU); palpebral fissure length was 13.34 ± 0.33 mm for OU; for horizontal corneal diameter was 10.72 ± 0.32 mm for OU; for vertical corneal diameter was 9.90 ± 0.30 mm for OU; for the hanging intraocular pressures was 19.38 ± 0.77 mmHg for OU; for upright IOP was 13.95 ± 0.60 mmHg for OU. Measurements for the individual species groups and eyes were also calculated. Conclusions Results revealed the IOP of bats in a hanging position were significantly higher than the IOP of bats in an upright position. The size of the bat, between the species, affected palpebral fissure length, horizontal corneal diameter, and vertical corneal diameter. Information about the ocular structures and normal ophthalmic parameters for the Pteropus species is crucial for species protection because of dependence on vision for survival.     

Tonometry in adult yellow-footed tortoises (Geochelone denticulata)

Objective To determine intraocular pressure (IOP) in adult yellow‐footed tortoises using applanation tonometry. Animals Fifteen healthy adult captive yellow‐footed tortoises (eight males and seven females). Procedures Intraocular pressures were estimated for tortoises by using an applanation tonometer after topical anesthesia. Body length, measured from nuchal to anal scutes, ranged from 27.5 to 57.2 cm. Five measurements from each eye were obtained by a single observer in an ambient temperature of approximately 30 °C. Results Mean ± SEM IOP of 30 eyes of 15 yellow‐footed tortoises was 14.2 ± 1.2 mmHg. Range of IOP was 6–30 mmHg for tortoises. Significant differences were detected neither between right and left eyes (P = 0.357) of individual tortoises, nor between males and females (P = 0.524). Observer's readability was good (intraclass coefficient = 0.65), and IOP did not change over the ordered five measurements. Conclusions There was no significant difference in IOP between males and females in this specie. Tonometry values for normal eyes may represent a useful diagnostic methodology for recognition and treatment of ocular diseases in reptiles.     

Use of Laparoscopy for the Evaluation of the Reproductive Status of Tench (Tinca tinca)

The aim of the study was to evaluate the use of laparoscopy for the assessment of the reproductive tract and stage of gonadal development of the tench (Tinca tinca). Laparoscopy was carried out from February to March 2009, on 30 anesthetized tenchs, 15 males and 15 females, of approximately 250 g bodyweight and 30 cm length, using a 1.9‐mm rigid cystoscope. Male and female gonads, attached to the swim bladder, were visualized. Testes were orange with a striped appearance. Mature ovaries were cluster‐shaped and whitish. Histological samples were collected, from the reproductive organs of both the sexes, with a forceps and showed the presence of gametes at different stages of maturity. The application of this minimally invasive diagnostic imaging technique could clinically be used as a powerful tool to evaluate the gender and to establish the reproductive status of tench and other fish.     

Distribution of Myxobolus cerebralis in Salmonid Fishes in Montana

Abstract

Over an approximately 2-year period, 20,974 fish (trout and other salmonid species) from 230 separate waters (creeks, rivers, lakes, reservoirs, ponds, hatcheries, and irrigation ditches) within 21 of the 22 major drainages in Montana were examined for Myxobolus cerebralis. Nine of the major river drainages have waters containing infected fish: Beaverhead, Big Hole, Blackfoot, Clark Fork above the Bitterroot River, Flathead below the south fork of the Flathead River, Jefferson, Madison, Missouri above the Marias River, and Yellowstone above the Bighorn River. The Beaverhead, Clark Fork above the Bitterroot River, Jefferson, Madison, and Missouri above the Marias River have the greatest number of waters containing fish infected with M. cerebralis. Comparisons of infection levels (number of pooled samples that contain fish infected with M. cerebralis) between species among these drainages show significantly lower levels of infection in brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss in the Missouri above the Marias River drainage and significantly higher levels of infection of rainbow trout in the Jefferson. Comparisons of differences in infection levels between drainages among species show that, in the Beaverhead, Clark Fork above the Bitterroot River, and Madison, infection levels in brown trout are significantly higher than in rainbow trout. This is partially attributed to losses of juvenile rainbow trout because of M. cerebralis infection, leading to biased samples. Histopathologic studies showed lesions were consistently less severe in brown trout than other species and occurred in a different location (gill arches versus ventral calvarium). In six of the nine affected drainages (Beaverhead, Blackfoot, Clark Fork above the Bitterroot River, Flathead below the South Fork, Jefferson, and Madison), infected fish were found at or near the time that intensive sampling was initiated in the spring of 1995. In the three remaining affected drainages (Missouri above the Marias River, Yellowstone above the Bighorn River, and the Big Hole), infected fish were not identified until at least 15 months after the initiation of widespread testing. This indicates that in the first six drainages listed above, the infection was well established prior to 1995 but spread into the last three drainages in the ensuing months. Methods of transmission and the sources of infection are unknown, although the absence of infected fish in state, private, and federal hatcheries in Montana indicates hatchery fish from these sources are not likely to be responsible.     

Physiological response of one of South Africa’s premier freshwater sport angling species,the Orange-Vaal smallmouth yellowfish Labeobarbus aeneus,to catch-and-release angling

The practice of catch-and-release fishing has been widely promoted by angling fraternities as a fisheries manage- ment tool. The aim of this investigation was to determine the physiological response of Orange-Vaal smallmouth yellowfish, Labeobarbus aeneus, to catch-and-release angling in the Vaal River, South Africa. Fish were collected using standard fly-fishing techniques, anaesthetised in clove oil and blood was drawn from the caudal vein; thereafter the fish were weighed, measured, revived and released. Blood plasma was analysed for concentra- tions of glucose, cortisol and lactate to determine the effects of angling duration, fish size and water tempera- ture. Larger fish were angled for a longer duration compared with smaller fish. Levels of glucose were affected by water temperature (influenced by time of year). Plasma glucose concentrations decreased with greater angling duration. Few individuals (n = 12) showed increased plasma cortisol concentrations. In extended-capture fish (angled for >1 min), lactate concentrations increased significantly above values for rapid-capture fish (angled for >30 s). These data suggest that catch-and-release causes physiological stress to fish, but nonetheless this practice can be a valuable fisheries management tool to ensure the sustainability of fish populations. Other factors beyond the ‘angling’ time are likely to contribute to physiological disruptions in homeostasis and therefore handling and air exposure of angled fish should be included in future catch-and–release angling studies. In addition, the longer-term impact of angling on fish health should also be determined.     

Metacercarial Distribution of Centrocestus formosanus among Fish Hosts in the Guadalupe River Drainage of Texas

Abstract

We examined the gills of wild fish collected from central Texas for Centrocestus formosanus metacercariae to determine whether this temperature-restricted parasite had invaded the thermally dynamic Guadalupe River via an introduced population in its thermally stable tributary, the Comal River. We collected fish from three sites in the Guadalupe River near its confluence with the Comal River (upstream, at, and downstream) and one site in the Comal River. Centrocestus formosanus infected 14 of the 25 species examined (56.0%) and 171 of the individual fish (27.1%). Several of the infected fish represent new host records for the parasite, and two are listed as species of special concern by the state of Texas. Mean metacercarial intensities varied from 8 to 616 among species, and the highest recorded intensity was greater than 800 in two Guadalupe roundnose minnow Dionda nigrotaeniata. Among the 24 species examined from the Guadalupe River, 11 (45.8%) were infected with C. formosanus. Thorough surveys at the study sites yielded no living specimens of the first obligate intermediate snail host (red-rim melania Melanoides tuberculatus), which must be present to perpetuate the parasite. Thus, the infections were probably due to drifting cercariae that had been shed into the water column upstream of the study area in the Comal River. We therefore investigated spatial patterns in cercarial acquisition using caged fish to determine whether drifting cercariae were present in the water column at the study sites. Of 57 uninfected blacktail shiners Cyprinella venusta exposed to Guadalupe River water downstream from and at the confluence, 52 (91.2%) became infected with C. formosanus metacercariae at a mean rate of 4 metacercariae/d. This finding extends the known geographic range of this invasive exotic parasite and is the first report of the life cycle being advanced in the fish assemblage of a thermally variable temperate stream in the USA.

Received October 18, 2010; accepted April 7, 2011     

Reproductive strategies in males of the world's southernmost lizards

Reproductive and life history patterns in reptiles are tightly related to the environmental conditions, so male reproductive cycles have been historically characterized as continuous, for tropical lizards, or seasonal, for temperate lizards. However, males of Liolaemus and Phymaturus lizards (Liolaemidae), from cold temperate climates of high altitudes or latitudes in Argentina and Chile, have developed a variety of reproductive cycles to coordinate with the short female reproductive season and to deal with the low frequency of reproductive females in the population. Using gonadal histology and morphological analysis, we describe the male reproductive biology, fat storage and sexual dimorphism of the viviparous lizards Liolaemus sarmientoi and Liolaemus magellanicus that inhabit an austral grass steppe at 51°S, in the southern limit of the American continent. Males of L. sarmientoi and L. magellanicus are reproductively available during the entire activity season of approximately 5 months. In addition, males of both species exhibit greater body sizes than females in morphological variables relevant in sexual selection. Meanwhile, females of both species exhibit larger inter‐limb length than conspecific males, which suggests fecundity selection to increase space for a larger litter size. The continuous sperm production throughout the activity season allows these liolaemids to mate at any time when females ovulate, representing a selective advantage to deal with the short activity season and the adversities of the cold environment they inhabit.     

Ivermectin in Senegalese Peulh Sheep: Influence of Sex on Plasma Disposition

The plasma disposition kinetics of ivermectin following a single subcutaneous administration of 0.2 mg/kg was investigated in male and female Senegalese Peulh sheep. Ten clinically healthy animals (5 males and 5 females) weighing 38–45 kg were used in this trial. Blood samples were collected by jugular puncture at different times between 0.5 h and 30 days post treatment. After plasma extraction and derivatization, samples were analysed by HPLC with fluorescence detection. Computerized kinetic analysis was carried out and mean parameters were statistically compared with the Mann–Whitney U-test. The area under the concentration–time curve (AUC) was significantly higher (p < 0.0027) in females than in males. Although the differences in maximum concentration (C _max), mean residence time (MRT) and half-life of elimination (t _1/2el) between males and females did not achieve statistical significance, values tended to be higher in females. Sex differences may be parallel with the level of storage in fat. Further investigations are required to improve the use of ivermectin in Senegalese sheep and findings may be used to predict optimal anthelmintic strategies for management of African species depending on the parasites present in a production system.     

The Effects of Whirling Disease on Growth and Survival of Snake River Cutthroat and Colorado River Rainbow Trout Fingerlings

Abstract

Two sizes of fingerling Snake River cutthroat trout Oncorhynchus clarkii behnkei and Colorado River rainbow trout O. mykiss were raised at hatcheries testing negative for Myxobolus cerebralis and stocked into the Dolores and Cache la Poudre rivers from 1999 to 2001. Populations were resampled over a 2-year period to determine which species and size combination had the highest growth and survival rates. Fish were tested for M. cerebralis via polymerase chain reaction and pepsin?trypsin digest analyses. Growth and survival rates between the species and size groups were not significantly different in either river. In the Dolores River, annual survival for both species and sizes of fish combined ranged from 0.063 to 0.12. In the Cache la Poudre River, survival for both sizes of rainbow trout was 0.004; survival for cutthroat trout ranged from 0.182 to 0.53. Larger fish had higher growth rates than smaller fish, and cutthroat trout had higher rates than similar sizes of rainbow trout. In both rivers, a higher percentage of the rainbow trout sample was infected than in the cutthroat trout sample. Rainbow trout also had a higher mean number of spores per head than cutthroat trout, and small rainbow trout had higher spore counts than large rainbow trout. Survival rates for cutthroat trout in the Cache la Poudre River were the highest of any of the groups, suggesting a difference that is biologically significant. Raising fingerlings to sizes greater than 100 mm can improve poststocking survival. If rainbow trout are stocked into contaminated waters, raising fingerlings to a larger size does not appear to improve growth or survival rates. Stocking rainbow trout in the spring could maximize growth rates but will expose fish to greater triactinomyxon densities, resulting in higher intensities of infection.     

Morphological analysis of the reproductive activity of Curimatella lepidura (Characiformes: Curimatidae)

Curimatella lepidura, commonly known as the manjuba, belongs to the Curimatidae family. To assess the reproductive activity of this species, fish were collected from three sections of the São Francisco River: section 1 = the Três Marias reservoir (TMR), section 2 = the SFR immediately downstream of the TMR, and section 3 = the SFR 54 km downstream from the TMR after the confluence of the SFR with the Abaeté River. Fish were collected bimonthly from January to December 2012. From this, the gonadosomatic index (GSI), Fulton condition factor (K), gonadal maturation stages in females and males, and diameters of vitellogenic follicles were determined. That is, this study employed histological and histometrical techniques to study the ovaries and testes of collected fish. The Fulton condition factor was statistically higher in section 1 than in the other sections, indicating that C. lepidura presents better health conditions in this section. Fish in the maturation/mature gonadal stage were collected in the November/December and January/February bimesters, coinciding with high temperatures, a long photoperiod, and abundant rainfall in this region. The mean vitellogenic follicle diameter was statistically lowest for sections 2 and 3, with a better impact on reproduction than in section 1. Overall, the results show that C. lepidura has reproductive success in lentic environments, such as in section 1, the TMR.     

Age estimation in the harbour seal (Phoca vitulina) based on the closure of skull sutures and synchondroses

Age estimation of individuals is an important tool for the management of marine mammals and is mostly done by microscopic analysis of growth layer groups (GLGs) in teeth (cementum and dentin) and bone. The present study evaluated the use of sutural and synchondrosal closure in the skull of the harbour seal (Phoca vitulina) as a potential non-destructive alternative for age estimation. For that, we scored the ectocranial closure of 12 selected sutures and synchondroses in a sample of 303 Eastern Atlantic harbour seals (P. v. vitulina; 138 males, 165 females), for which data on age at death were available, based on determined gross-morphological criteria in individuals younger than 1 year and cement layer analysis in canines in older individuals. A strong positive relationship between the sum of closure level scores (SCS) and age (males: r = 0.8797, females: r = 0.8825) was recorded, which was stronger than that for the relationship between age and condylobasal length (CBL, males: r = 0.7085, females: 0.7086) (all p-values <0.0001). In adult individuals (≥5 years), CBL was higher in males than females (p < 0.0001), while SCS did not significantly differ between the two sexes (p = 0.148). Our findings show that the analysis of sutural/synchondrosal closure is a valid alternative for age estimation in harbour seals, thereby confirming results of previous studies on other pinniped species.     

Contributions to the Biology of the Panga Pterogymnus Laniarus (Pisces : Sparidae): Age,Growth and Reproduction

All the fish used in this investigation were caught by commercial side trawlers along the eastern Cape coast of South Africa. Age and growth of P. laniarius was determined from otoliths collected monthly from April 1974 to September 1975. The validity of annuli was proved by monthly edge examination of the otoliths. There is no difference in growth between the sexes. The Von Bertalanffy equation L_t = 48,1 (l-e^{-0,10(e + 0.22)}) was found to describe the growth of the panga in length. Some fish become sexually mature at a total length of 26 cm. Fifty percent maturity is attained at a length of 28 cm, between the ages of 4 and 5 years. All fish are sexually mature at a total length of 32 cm, at an age of 6 years. The spawning season of the panga extends from mid-September to May.     

Reproduction of Labeo umbratus (Pisces,Cyprinidae) in Wuras Dam,a shallow,turbid impoundments

Female Labeo umbratus reach sexual maturity at a larger size than males and dominate the population in fish over 450 mm in length. The gonads are large (up to 20% of total body mass) and they have a high fecundity which increases linearly with an increase in body mass. Successful spawning is dependent on suitable floods during the spawning season which extends from November to March or April. Spawning apparently occurred in the impoundment. All females did not spawn simultaneously and evidence suggests that individuals might spawn more than once during a particular season.     

Sexual size dimorphism in the lizard Oplurus cuvieri cuvieri (Squamata,Opluridae) from Madagascar

Sexual size dimorphism in the medium-sized lizard Oplurus cuvieri cuvieri, which is endemic to the dry deciduous forest of Madagascar, is presented. Adults are sexually dimorphic in body size, head size, and tail length. Males have a greater snout–vent length (SVL), head depth, head width, jaw length, tail length and body mass than females. Juvenile males have greater annual SVL growth rates than juvenile females, contributing to adult sexual size dimorphism. Moreover, the rates of increase in head depth and width differ significantly between the sexes after reaching maturity so that adult males have larger heads for a given body size than adult females. I suggest three proximate mechanisms that may cause sex-related differences in adult head size of O. c. cuvieri based on natural selection; to reduce intersexual food competition, sexual selection involving mate acquisition in males, and ontogenetic change of allometry to improve reproductive output in females.