Experimental evaluation of a minnow trap for small lotic fish

A minnow trap that operates in various flow regimes in streams and allows sampling of small fish from stream bed microhabitats was developed. In laboratory and field tests, the most efficient trap design for capturing and retaining various species of fish had one funnel oriented downstream, a plexiglass body, and commercial trout food as bait. These lightweight traps can be set in a wide range of current velocities and depths, and can be useful in investigations that examine the microhabitat use, diel activity patterns or population densities of small lotic fish. Guidelines for the trap's use and for quick verification of capture success in new situations are suggested.     

Generalization of learned predator recognition: an experimental test and framework for future studies

While some prey species possess an innate recognition of their predators, others require learning to recognize their predators. The specific characteristics of the predators that prey learn and whether prey can generalize this learning to similar predatory threats have been virtually ignored. Here, we investigated whether fathead minnows that learned to chemically recognize a specific predator species as a threat has the ability to generalize their recognition to closely related predators. We found that minnows trained to recognize the odour of a lake trout as a threat (the reference predator) generalized their responses to brook trout (same genus as lake trout) and rainbow trout (same family), but did not generalize to a distantly related predatory pike or non-predatory suckers. We also found that the intensity of antipredator responses to the other species was correlated with the phylogenetic distance to the reference predator; minnows responded with a higher intensity response to brook trout than rainbow trout. This is the first study showing that prey have the ability to exhibit generalization of predator odour recognition. We discuss these results and provide a theoretical framework for future studies of generalization of predator recognition.     

Distribution and biology of Galaxias truttaceus (Galaxiidae) in south-western Australia, including first evidence of parasitism of fishes in Western Australia by Ligula intestinalis (Cestoda)

The freshwater trout minnow, Galaxias truttaceus, is restricted to the small catchments of the Goodga and Kalgan Rivers in Western Australia. Its large geographic separation from populations in south-eastern Australia, and subsequent reproductive isolation and variation in the prevailing environmental conditions, has created marked differences in biology (and morphology) between the eastern and western populations of G. truttaceus. The biology (spawning period, longevity, growth rates, diet and parasitism) of G. truttaceus in the Goodga River is described and then compared with information on the biology of diadromous and landlocked populations in south-eastern Australia (i.e. Tasmania) (see Humphries 1989). In the Goodga River, ca. 34 and 8% of males and females, respectively, attain maturity at the end of their first year, while only four mature males and one mature female 0+ fish were found in the Tasmanian populations. Adults migrate upstream prior to spawning which peaks during April and May. Larvae, which hatch at ca. 6.5mm (cf. 7.5–9.0mm in Tasmania), move downstream into Moates Lake for a few months before re-entering the river. Of the 810 G. truttaceus collected, ca. 53, 34, 10, 2, 1, 0.2 and 0.1% belonged to the 0+, 1+, 2+, 3+, 4+, 5+ and 7+ age classes, respectively. In contrast, the Tasmanian populations have a much higher proportion of older fish. At the end of their first, second and third years, the males on average attain 60, 84 and 95mm total length (TL), respectively, whereas females attain 63, 89 and 103mm TL, respectively at those ages. Only one fish > 140mm TL was captured, which contrasts with the Tasmanian fish, where a substantial proportion are > 140mm TL. The diet of fish > 40mm TL consisted of between 65 and 96% terrestrial fauna (mainly coleopterans and hymenopterans) in the different seasons. Larval fish diets were largely comprised of copepods.The occurrence of the introduced cestode Ligula intestinalis in ca. 7% of G. truttaceus represents the first record of this parasite in Western Australia. It was found to cause gonadal retardation and gross morphological deformities, the latter of which possibly increases the risk of avian predation.     

稀有鮈鲫性别决定类型初探

稀有鮈鲫(Gobiocypris rarus)是中国特有的一种小型鲤科鱼类,属于亚科、鮈鲫属,俗称金白娘、墨线鱼,主要分布于四川省汉源县大渡河支流的流沙河及成都附近的一些小河流中,被中国野生动物红皮书列为濒危鱼类。       

Competition-induced switch in young of the year perch,Perca fluviatilis: an experimental test of resource limitation

Synopis Reproductively developed male fathead minnows, Pimephales promelas, exhibited courtship behaviour in the presence of female conspecifies under laboratory conditions. Male courtship consisted of several distinctive and visually conspicuous behaviours directed toward females, including approach, display, and two contact behaviours, as well as leading behaviour from the female to a suitable spawning site. An ovulated condition in females was not necessary to generate male courtship behaviour; in fact, the amount of courtship exhibited by males may depend inversely on the readiness of females to spawn.     

The identification of apolipoprotein genes in rare minnow (Gobiocypris rarus) and their expression following perfluorooctanoic acid exposure

Apolipoproteins play important roles in lipid transport and uptake in vertebrates, and they are associated with pathogenesis of many cardiovascular diseases. However, the diverse apolipoproteins in individual fish species have not been extensively characterized. Partial cDNA sequences encoding ApoA-IV, ApoE, ApoM, ApoL, and ApoO, and full-length cDNA sequences encoding ApoA-I were cloned from rare minnow (Gobiocypris rarus). Sequence analysis showed that these genes, as well as fragments of other known apolipoprotein genes (ApoC-I, ApoC-II, ApoB) of rare minnow had a high similarity (91–96%) to their orthologues in the spotted barbel Hemibarbus mylodon (Teleostei:Cypriniformes). The expression of these nine genes and their possible upstream genes, PPARα, PPARγ, and HNF4α, were investigated in rare minnow after subacute exposure to perfluorooctanoic acid (PFOA) for 14 days. Results showed that the expression of mRNA for ApoA-I, ApoC-II, and ApoM was significantly downregulated in all PFOA-treated animals. Only fish receiving the highest dose of PFOA showed downregulation of the expression of ApoA-IV and ApoC-I, while fish treated with 10 mg PFOA/L showed upregulation of expression of ApoE. Expression of ApoB, ApoO, and ApoL was unchanged between control and treated groups. In addition, the expression of PPARα was increased in all dosed fish, while the mRNAs for PPARγ and HNF4α were significantly altered with 30 and 3 mg PFOA/L doses, respectively. Therefore, subacute exposure to PFOA resulted in alteration of expression of apolipoproteins and related genes. These changes in gene expression may further influence lipid metabolism or other physiological functions in fish.     

Free—living fathead minnows rapidly learn to recognize pike as predators

Individuals from a natural population of approximately 20 000 fathead minnows from a pike–free pond did not respond with appropriate anti–predator behaviour upon encountering pike odour in laboratory tests. However, 14 days after 10 pike were stocked into the pond, minnows had acquired recognition of pike odour. Laboratory studies have indicated several possible mechanisms for acquiring predator recognition in fathead minnows. This study indicates that these, or similar processes, can produce major changes in predator recognition in the wild.     

Effects of handling on endocrinology and reproductive performance of the fathead minnow

Anaesthesia with MS-222 followed by intra-peritoneal (ip) injection (with a 10% ethanol in corn oil carrier) of fathead minnow either as one or three (weekly) treatments did not affect survival, behaviour or secondary sexual characteristics of the fish. Fecundity of the fish, as indicated by fertility and hatching success, was also unaffected. Gonadal condition (relative gonad mass, histopathology) was not altered in either sex. Male and female plasma sex steroids (β;-oestradiol, testosterone, 11-ketotestosterone) and male vitellogenin concentrations were not significantly affected by the treatments. Females subjected to either ip treatment regime had significantly higher plasma vitellogenin concentrations than control females. However, based on previous data, this difference did not appear to be treatment-related. Overall, exposure of fathead minnows to chemicals via the ip route should not confound the interpretation of toxicity tests with potential endocrine disrupting chemicals.     

Characterization of microsatellite loci in the creek chub (Semotilus atromaculatus)

Thirty‐two polymorphic microsatellite loci (29 novel, 3 cross‐species) are characterized in the creek chub, Semotilus atromaculatus, a widespread and abundant North American minnow. Novel repeat‐containing sequences were isolated using a standard microsatellite enrichment procedure. A set of di‐, tri‐, and tetranucleotide markers with allele numbers ranging from two 16 are now available for estimating relatedness within and among populations in this ecologically important species.