Response of seaward-migrating European eel (Anguilla anguilla) to manipulated flow fields

Anthropogenic structures (e.g. weirs and dams) fragment river networks and restrict the movement of migratory fish. Poor understanding of behavioural response to hydrodynamic cues at structures currently limits the development of effective barrier mitigation measures. This study aimed to assess the effect of flow constriction and associated flow patterns on eel behaviour during downstream migration. In a field experiment, we tracked the movements of 40 tagged adult European eels (Anguilla anguilla) through the forebay of a redundant hydropower intake under two manipulated hydrodynamic treatments. Interrogation of fish trajectories in relation to measured and modelled water velocities provided new insights into behaviour, fundamental for developing passage technologies for this endangered species. Eels rarely followed direct routes through the site. Initially, fish aligned with streamlines near the channel banks and approached the intake semi-passively. A switch to more energetically costly avoidance behaviours occurred on encountering constricted flow, prior to physical contact with structures. Under high water velocity gradients, fish then tended to escape rapidly back upstream, whereas exploratory ‘search’ behaviour was common when acceleration was low. This study highlights the importance of hydrodynamics in informing eel behaviour. This offers potential to develop behavioural guidance, improve fish passage solutions and enhance traditional physical screening.     

Factors affecting the activity of two species of eel (Anguilla spp.) in a small New Zealand lake

Fyke net captures of both the shortfinned eel, Anguilla ausrralis Richardson, and the longfinned eel. A. dieffenbachü Gray, were recorded over a 4-year period in Lake Pounui. New Zealand. Eel activity measured as catch per unit effort (CPUE) was correlated to 36 indices of water temperature water level, barometric pressure, amount of light at night and lunar period using multiple regression analysis. For longfinned eels, water temperature was the only individual parameter significantly related (P<0.001) to CPUE. The multiple regression model was improved (R²= 0.29. P <0.01) by the addition of lunar phase and change in barometric pressure. Water level was the most important parameter in the model for shortfinned eels, although water temperature and change in barometric pressure were significant influences in the predictability of the model (R²= 0.51. P<0.001.     

Microsatellite markers discriminate three species of North Atlantic wolffishes (Anarhichas spp.)

Sixteen tetranucleotide and dinucleotide microsatellite markers were isolated from Atlantic wolffish, Anarhichas lupus , following a microsatellite enrichment procedure using probe-labelled magnetic beads. These microsatellites were intended for use in Atlantic wolffish as well as in two closely related species, spotted wolffish, Anarhichas minor , and northern wolffish, Anarhichas denticulatus . As all three species are of conservation concern in Canadian waters and as forensic wildlife cases may arise for this genus, microsatellite markers were assessed to determine how well they differentiate these species from one another and to estimate probability values that could be expected for identification of individuals to species.     

Early marine migration of European silver eel Anguilla anguilla in northern Norway

To study the migratory behaviour in wild northern European silver eel Anguilla anguilla during sea entry and early marine migration, 32 individuals were tagged with acoustic transmitters and registered at four automatic listening station arrays from the mouth of the north Norwegian River Alta and throughout the Alta Fjord. The A. anguilla entered the fjord during all parts of the tidal cycle and did not seem to utilize the outgoing tidal currents. They migrated mainly during the night, in both the river mouth and the fjord. On average, they spent 2·7 days travelling from the river mouth to the outermost array, 31 km from the river mouth, corresponding to an average migratory speed of 0·5 km h(-1) . The A. anguilla generally migrated in the central part of the fjord and in the uppermost 10-25% of the water column, but with frequent dives to greater depths. Already 4 km after sea entry, A. anguilla were observed diving deeper than 130 m within 20-30 min periods. Hence, this study demonstrated that A. anguilla may perform an active diving behaviour during the early marine migration. The study took place in a pristine area with a minimum of anthropogenic interventions and by individuals from a population still uninfected by the introduced parasite Anguillicoloides crassus. The results may therefore be used as a baseline for future studies of the A. anguilla early marine migration.     

Olfactory sensitivity to amino acids in the juvenile stages of the European eel Anguilla anguilla (L.)

Scanning electron micrograph observations of the olfactory mucosa from both unpigmented glass eel(GE)andpigmentedelvers(EL)of the European eel, Anguilla anguilla (L.), revealed the presence of various cell types; amongst these, the ciliated and microvillous ones are likely to possess a chcmosensory function. Recording of underwater electro-olfactograms (EOGs) showed that various amino acids (glycine, L-alanine, L-valine, L-leucine, L-asparagine, L-glutamine and L-methionine) are effective stimulants for the olfactory mucosa. Dose response curves of stimulus concentrations v. EOG amplitudesfit regression linesat both GE and EL stages. Leucine was more stimulatory at the GE than at the EL stage. The stimulatory effect of the other six amino acids tested was similar at both developmental stages. The possible role of olfactory sensitivity in animal behaviour at different developmental stages is discussed.     

Diel movement of smallmouth yellowfish Labeobarbus aeneus in the Vaal River,South Africa

Diel movements of Orange–Vaal smallmouth yellowfish Labeobarbus aeneus (Burchell, 1822) in the Vaal River, South Africa, were determined by externally attaching radio transmitters to 11 adult fish and manually tracking them between March and May 2012. Twenty-four radio telemetry monitoring surveys produced 2 304 diel tracks. At night, yellowfish displayed a preference for slow shallow (<0.3?m s?1, <0.5?m) and fast shallow habitats (>0.3?m s?1, <0.3?m), whereas by day they avoided these habitats, preferring fast deep areas (>0.3?m s?1, >0.3?m). The average total distance of 272?m moved per 24-hour period was three times greater than the diel range, and the average maximum displacement per minute was significantly higher in daytime (4?m) than at night (1.5?m). These findings suggest that L. aeneus is active primarily during the day in fast-flowing, deeper waters, and relatively inactive at night, when it occupies shallower habitats. This behaviour should be further explored to identify causal mechanisms underlying the diel habitat shifts in this species such as water temperature, foraging tactics and/or predator avoidance.     

Effects of passive integrated transponder tags on short-term feeding patterns in European perch (Perca fluviatilis)

We tested the feeding behaviour of small European perch (Perca fluviatilis) in a laboratory study during the first 24 h after handling and 23 mm passive integrated transponder (PIT) tag implantation. Feeding commenced almost immediately following tagging and overall feeding patterns were unaffected by tagging. However, untagged perch had more feeding events than PIT-tagged individuals. This discrepancy could be attributed to post-tagging effects or/and reduced room for food due to the presence of the tag in the body cavity.     

Short‐term evaluation of visible implant alpha tags in juveniles of three fish species under laboratory conditions

Visible implant alpha (VI alpha) tag‐induced changes in mortality and condition, as well as tag retention and readability, were examined during a 4‐week period for juveniles of three fish species: tiger muskellunge Esox masquinongy × Esox lucius (91 ± 7 mm total length, L_T, mean ± s.d.), Snake River cutthroat trout Oncorhynchus clarki behnkei (84 ± 8 mm) and rainbow trout Oncorhynchus mykiss (85 ± 5 mm). Mortality and condition did not differ between tagged fish and control fish for any species and overall tag retention rates were high (92% for E. masquinongy × E. lucius, 91% for O. c. behnkei and 100% for O. mykiss). Short‐term readability of VI alpha tags was low in juvenile E. masquinongy × E. lucius and juvenile O. c. behnkei. Therefore, it is not recommend to use VI alpha tags in juvenile E. masquinongy × E. lucius or juvenile O. c. behnkei for periods >2 weeks, but VI alpha tags seem to be suitable for juvenile O. mykiss for a period of at least 4 weeks.     

Activity and food choice of piscivorous perch (Perca fluviatilis) in a eutrophic shallow lake: a radio-telemetry study

SUMMARY 1. Radio transmitters were implanted in large perch (27–37 cm) in a shallow lake in Denmark. Between 6 and 13 perch were tracked every 3 h for 24‐h periods twice (summer) or once a month (winter) from August 1997 to July 1998. Activity levels were recorded as minimum distance moved per hour. 2. No significant differences in activity levels of individual fish were observed. 3. Highest activities were observed at daytime with peaks at dawn and dusk or midday. This diel pattern was most pronounced from October to April, whereas diel variations were less in the summer months, with no peaks occurring in midsummer. The general lack of activity at night supports the idea that perch is a visually oriented forager. 4. There was no significant relationship between daytime activity during the year and temperature or day length, but nighttime activity was correlated with temperature. In contrast with previous findings, activity levels varied little seasonally, except for high activity levels that occurred concomitantly with high temperatures in August. Instead, we found a significant relationship between the total distances moved per day and temperature, indicating that perch moved at the same average speed in the wintertime, but did so for shorter periods than in summer because of shorter day lengths. 5. Diet of the tagged perch shifted from fish dominance between August and January to invertebrates from February to June. There was no correlation between the diet shift and activity levels, indicating that feeding on invertebrate requires similar activity levels as predation on fish. 6. The results of this telemetry study throughout a year suggest that perch are more active during the winter than previously inferred from gill‐net catches. This observation underscores the importance of perch as a predator of 0+ planktivorous fish in lakes and has potential implications for pelagic food web structure and lake management by biomanipulation.     

Mixed species flocking of tits (Parus spp.): a field experiment

Summary We tested two general models of flocking behaviour, namely the antipredation model and foraging efficiency model on mixed-species tit flocks (Parus spp.). After food addition the size of mixed-species flocks was significantly less than in the control samples. In the presence of extra food significantly more birds were observed either in monospecific flocks or solitary, than during the control observations. In the presence of a living predator the birds foraged in larger mixed-specifies flocks than during the control observations. In addition, the social behaviour of Great Spotted Woodpecker, Middle Spotted Woodpecker and Nuthatch shifted to mixed-specific flocking. The size of monospecific flocks was independent of both treatments. The density of birds increased significantly after food addition, while in the predator presence the birds tended to leave the forest. These results support the view that both the antipredation model and foraging efficiency model seem to be valid for mixed-species flocking. However, in the case of monospecific flocks, the territory maintenance could be the most important factor.     

Taxonomic implications of diterpene alkaloids in three toxic tall larkspur species (Delphinium spp.)

The diterpene alkaloid content was used to assess the chemical taxonomic diversity in three larkspur species. Samples (n=163) were collected from 18 different locations in five western states, extracted and analyzed for diterpene alkaloids using electrospray mass spectrometry. The data were statistically analyzed using canonical discriminant analysis and analysis of variance. Delphinium glaucum samples were easily grouped and were significantly different from all other groups (P<0.005) for two compounds. Delphinium barbeyi and Delphinium occidentale were found to be distinct groups, but more closely related. Samples representing a putative hybrid between D. barbeyi and D. occidentale were found to be closely related to D. occidentale, but were significantly different from all other groups. These data support the classification of D. glaucum, D. barbeyi, and D. occidentale as distinct species and suggest that a possible hybrid is more similar to D. occidentale than D. barbeyi.     

Redescription of Heliconema africanum (Linstow, 1899) n. comb. (Nematoda: Physalopteridae), a nematode parasite of freshwater eels (Anguilla spp.) in South Africa

The little-known nematode species Heliconema africanum (Linstow, 1899) n. comb. (Physalopteridae) is redescribed based on light and scanning electron microscopical examinations of specimens collected from the stomach of the African longfin eel Anguilla mossambica (Peters) in the Nahoon River, Eastern Cape Province, South Africa. This species, previously misidentified as Heliconema longissimum (Ortlepp, 1922), is a common parasite of eels in South Africa. The systematic status of H. longissimum, a species originally described from unidentified Australian snakes, is unclear and probably several morphologically closely related species have been included under this name.     

Food of three sympatric gadfly petrels (Pterodroma spp.) breeding on the Pitcairn Islands

Food samples were collected from 29 Herald petrels Pterodroma heraldica , 27 Kermadec petrels P. neglecta and 37 Murphy's petrels P. ultima , on the Pitcairn Islands during 1991. 92% of samples were from chicks. Food items comprised cephalopods (in 86–92% of samples) of 22 species, fish (in 24–41% of samples) of at least four families, crustaceans (in 10–38% of samples) including mysids, an amphipod, an isopod and unidentified decapods, insects– marine water striders Halobates (in 59–66% of samples), coelenterates (in 0–8% of samples), tunicates (in 0–7% of samples), and traces of offal (cetacean or shark), plastics and pumice. Only cephalopods were sufficiendy numerous and identifiable to enable a comparison of the three petrels' diets. Herald petrels mainly fed on juvenile ommastrephids, whereas Murphy's petrels mainly ate vertically-migrating, bioluminescent cranchiids, histioteuthids and onychoteuthids; Kermadec petrels were intermediate between them. Such differences might have resulted from the different dates when, or different islands where, most samples were collected from each species; or differences in feeding ranges or times of feeding between species; or to species' preferences.     

Activation of three species of tsetse (Glossina spp.) in response to host derived stimuli

Recordings were made of the activation of hungry Glossina morsitans morsitans Westwood, G. pallidipes Austen, and G. austeni Newstead in response to odours from ox breath and ox urine, and a moving visual stimulus, in a wind tunnel. The spontaneous activity of G.m.morsitans was very low (less than 4% of males and 2% of females active per min during control periods). That of G.austeni and G.pallidipes was in the region of 20% except for G.pallidipes females when in excess of 40% were active during control periods. Addition of ox urine odours to the airstream had no effect on activity in any of the species investigated but addition of ox breath odours to the airstream significantly increased activity of G.pallidipes and of G.m.morsitans, although for the latter only approximately 12% of flies were active. For G.austeni the addition of ox breath odours resulted in a significant increase in activity of females but not of males. The moving visual stimulus resulted in a significant increase in the activity of both sexes of G.austeni and G.m.morsitans but no change in the activity of G.pallidipes. The low level of spontaneous activity and the low response to ox breath odours in a strain of G.m.morsitans maintained in the laboratory since 1969 was compared with a new colony of this species which originated from puparia collected in Zimbabwe in 1991. No differences in either spontaneous activity or the response to ox breath odour was recorded, but females from the new colony were significantly more responsive to a moving visual stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plant species richness and composition a long livestock grazing intensity gradients in a Namaqualand (South Africa) protected area

The study described changes in floristic and vegetation structure in relation to livestock grazing intensity in a conservation area in the Succulent Karoo, South Africa. Grazing by goats and sheep is allowed in the Richtersveld National Park (a contractual National Park. which is also an area of high floristic richness and endemism. We used goat faecal pellet density, degree of trampling and percentage bare-ground at distances from the stock posts as surrogates for a gradient in grazing pressure. A stock post is the place where farmers keep, in most cases in an enclosure called a ‘kraal’, their animals at night and to which they return every evening after the day’s herding. Twenty-seven stock posts were located in the Richtersveld National Park; nine stock posts on flats, foot– slopes and mountain each. We measured plant species richness and diversity, and mean percentage cover of the various plant growth forms (including the number of species falling into each growth form category. in each of the five 10 m . 10 m plots (each 200 m apart. demarcated along a transect of one kilometre length from the centre of each stock post. The results showed that distance from the stock post does reflect grazing intensity use because densities in faecal pellets rapidly declined with increasing distances away from the stock post for all habitats studied. Faecal density was positively correlated with stocking density. Plant species richness and diversity was at a minimum near stock posts. Plants able to endure the effects of heavy grazing occurred near stock posts where declines in palatable plant species, assumingly sensitive to heavy grazing and trampling, were recorded. Grazing increased vegetation patchiness up to 800 m from the stock post for all the habitats. The degree to which this change in species composition occurred did not depend on stocking densities, suggesting that both grazing and landscape variability were responsible for vegetation changes in rangelands of that area of the Succulent Karoo biome.     

Paraquimperia Africana n. sp (Nematoda : Quimperiidae), a new intestinal parasite of the eel Anguilla mossambica Peters, in South Africa

A new seuratoid nematode of the family Quimperiidae, Paraquimperia africana n. sp., is described from the small intestine of the longfin eel, Anguilla mossambica Peters, from the Eastern Cape Province, South Africa. The new species is characterized mainly by the presence of a ventral sucker in mature males, short spicules (147-171 microm), the number and arrangement of caudal papillae, the postesophageal position of the excretory pore, and by the slender female tail. In this new species, a variability in the number (3-5 pairs) of subventral preanal papillae was observed. Paraquimperia africana is the first representative of the genus in Africa. In view of recent reports, Paraquimperia aditum (Mueller, 1934) is considered a junior synonym of Paraquimperia tenerrima (Linstow, 1878). Paraquimperia xenentodonia Gupta and Bakshi, 1984 is considered a species inquirenda.     

Meiotic abnormalities in sugarcane (Saccharum spp.) and parental species: Evidence for peri- and paracentric inversions

The modern cultivars of sugarcane (Saccharum spp.) are highly polyploid and accumulate aneuploidies due to their history of domestication, genetic improvement and interspecific hybrid origin involving the domesticated sweet species Saccharum officinarum (‘noble cane’) and the wild Saccharum spontaneum, both with an evolutionary history of polyploidy. The first hybrids were backcrossed with S. officinarum, and selection from progenies in subsequent generations established the genetic basis of modern cultivars. Saccharum genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture and cytogenetics. Herein, we conducted a comparative analysis of the meiotic behaviour of representatives of the parentals S. officinarum and S. spontaneum, and the commercial variety, SP80-3280. S. officinarum, an octoploid species, exhibited regular meiotic behaviour. In contrast, S. spontaneum and SP80-3280 exhibited several abnormalities from metaphase I to the end of division. We reported and typified, for the first time, the occurrence of peri- and paracentric inversions. Using in-situ hybridisation techniques, we were able to determine how pairing association occurred at diakinesis, the origin of lagging chromosomes and, in particular, the mitotic chromosome composition of SP80-3280. Interestingly, S. spontaneum and recombinant chromosomes showed the most marked tendency to produce laggards in both divisions. Future attempts to advance knowledge on sugarcane genetics and genomics should take meiotic chromosome behaviour information into account.