The use of PIT telemetry to study movements of ammocoetes and metamorphosing sea lampreys in river beds

Passive integrated transponder (PIT) tags were surgically implanted in 118 sea lamprey Petromyzon marinus ammocoetes which were left to recover in the laboratory for 2 months. During this period 55 individuals started to metamorphose. In the late summer of 2002 the tagged animals were released in a small tributary of the River Mondego, Portugal, and were regularly monitored for a period of 2 months using a portable PIT tag reader. The distribution of the released animals changed from an initial uniform pattern to a random distribution, and then to an aggregated pattern. At the end of the first week 60% of the tagged sea lampreys had already left the study area, indicating their dynamic behaviour. Ammocoetes were more active than metamorphosing sea lampreys, and downstream movements were more frequent when compared to the upstream ones, which were usually a short distance. In order to determine the influence of the dark‐light cycle in the diel activity rhythms, 10 tagged sea lamprey ammocoetes were released in a tank (2000 l capacity) and their position monitored twice a day, for a period of 1 month. Ammocoetes locomotor activity appeared to be conditioned by circadian rhythms, and they were particularly active during darkness.     

Patterns of growth and smolting in autumn migrants from a Scottish population of Atlantic salmon, Salmo salar L.

In late November 1990 salmon parr, Salmo salar L., from the Girnock Burn in northern Scotland were either caught on their feeding territories (n=25) or trapped during downstream migration (n= 18). They were then housed in a laboratory rearing tank and their food intake and growth rates were tracked, until their smolting status was ascertained in the following May. Female fish were predominant in both groups; although the range of ages was the same, the total age of migrants was 2+ while that of residents was 1+. In November, compared to resident fish of the same year class, migrants were larger, heavier and in better condition. Although growth rates dropped during the winter in both groups before increasing in spring, migrants ate more and consistently grew faster than residents. In seawater tolerance tests conducted in May, more residents than migrants failed to adapt. These results confirm the suggestion that autumn migrants smolt in the following spring and suggest that they represent the faster-growing component of their cohort.     

Muscle glycogen, lactate and glycerol-3-phosphate concentrations of larval and young adult lampreys in response to exercise

When stimulated, the ammocoetes (larvae) of Geotria australis swim continuously at a moderate rate for only approximately 20 min, whereas the downstream migrants (young adults) of this species did not become exhausted following similar swimming activity over the same period. Mean concentrations of muscle glycogen in ammocoetes declined during exercise, but returned to resting levels within 30 min of recovery, whereas those in young adults changed little during the corresponding periods. Moreover, muscle lactate concentrations of ammocoetes rose markedly during exercise and the first 30 min of recovery, before declining significantly, while those of young adults remained similar during and immediately after exercise. Calculations, using the glycogen and lactate concentrations immediately after exercise, suggest that during exercise glycogen is, to some extent, utilised anaerobically (approx. 24%) by ammocoetes, but only aerobically by young adults. Furthermore, since young adults used only a small amount of glycogen, they presumably metabolised triacylglycerol aerobically to produce energy. Muscle glycerol-3-phosphate levels were far higher prior to and immediately after exercise in downstream migrants than in ammocoetes and then declined precipitously. The above trends in muscle glycogen and lactate of larval G. australis parallels, to some degree, those recorded by other workers for upstream migrant Petromyzon marinus that had been exercised to exhaustion.     

Structure and Development of the Notochord ‘Elastica Externa’ and Nearby Components of the Elastic Fibre System of Agnathans

Between 15 days and 3 months in age, the ‘elastica externa’ of the notochord sheath of larval lampreys develops from patches of moderately dense and amorphous material into a thick, continuous and electron-dense layer. In both lampreys and hagfish, this layer stains strongly with Verhoeff's elastic stain and aldehyde fuchsin and is penetrated by collagen fibrils on both its outer and inner boundaries. Peroxidase labelling using an antibody raised against human elastin specifically labels both the notochord ‘elastica externa’ and the elastic fibre system of lampreys. The diameters of the microfibrils (10–13 nm) of the oxytalan, elaunin and elastic fibres of lampreys and hagfish are the same as those of higher vertebrates. The connective tissue immediately dorsal and ventral to the notochord of lampreys contains mainly oxytalan fibres in very young ammocoetes, a combination of oxytalan, elaunin and elastic fibres in older ammocoetes, and predominantly elastic fibres in adult lampreys. While the region of the endomeninx at the base of the spinal cord contains almost exclusively oxytalan fibres in young ammocoetes, it also possesses numerous elastic fibres in adult lampreys. These findings indicate that, as in higher vertebrates, the elastic fibres of lampreys develop from oxytalan fibres via elaunin fibres.     

Larval growth in the river lamprey, Lampetra fluviatilis

A series of 987 ammocoetes from the rivers Towy, Teme, and Taw have been identified as mainly L. fluviatilis (L.) on the basis of oocyte counts on female ammocoetes. The length frequency distributions for this material differs from either L. planeri or P. marinus in showing only three modes in addition to the young of the year and the length distribution of the final mode coincides with the length range for 119 metamorphosing and macrophthalmia stages of L. fluviatilis that have been found at the same sites. These animals measured from 80–117 mm in length and weights varied from 0.76–2.28 g. Metamorphosis is believed to take place in late summer and early autumn when in the majority of cases, the ammocoetes are four and a half years old. The evidence that the non-parasitic L. planeri has a longer larval life than the closely related parasitic L. fluviatilis is thought to have some significance in relation to the evolution of the brook lamprey species.     

Annual movement and migration of adult pikeperch in a lowland river

The downstream migration of 46–66 cm radio-tagged adult pikeperch Stizostedion lucioperca , in the River Gudenaa, Denmark, from late September to late December, coincided with a reduction in the frequent occurrence of prey fish in the tagging area, and hence was interpreted as a feeding migration. The upstream migration from March to mid-April in spring took place prior to spawning which occurred from late April to June.     

Variations of life history strategy of the arctic lamprey <Emphasis Type="Italic">Lethenteron camtschaticum</Emphasis> from the Utkholok River (Western Kamchatka)

Morphobiological traits of the lamprey from the Utkholok River (Western Kamchatka) are investigated for the first time. All present forms of lamprey (typically anadromous, anadromous early maturing forma praecox, resident) do not differ by diagnostic characters and belong to one species Lethenteron camtschaticum. Males prevail among mature specimens of various forms, smolts, and ammocoetes at later developmental stages. The forma praecox is represented by males by 92%. A hypothesis is suggested explaining the relationships of the forms and the mechanism of realization of different types of life history strategy in relation to energy resources of water bodies and the kind of feeding of different groups of ammocoetes (organic detritus or Pacific salmon carcasses decomposed after spawning).     

An electrophoretic and immunoelectrophoretic study of serum proteins during the life cycle of the lamprey, Petromyzon marinus L

Serum proteins of upstream migrants, parasitic adults, early and late metamorphosing animals, and ammocoetes of Petromyzon marinus L. were examined by polyacrylamide gel electrophoresis and crossed-immunoelectrophoresis. The electrophoretic patterns for two proteins, SDS-1 and CB-III, were found to change during the life cycle. quantitative measurements of these two proteins showed that they continued to increase until in the adult they together constituted approx. 85% of the total serum protein. Evidence was obtained for a protein present in ammocoetes and metamorphosing animals, but not in upstream migrants.     

Growth and movements of the twaite shad, Alosa fallax (Lacépède), in the Severn Estuary

Between July 1974 and April 1977, appreciable numbers of 0 group twaite shad, Alosa fallax , have been collected from the cooling water intake screens of the Nuclear Power Stations at Oldbury-upon-Severn and Berkeley on the Severn Estuary and at Hinkley Point on the Bristol Channel, England. Young of the year first appeared at Oldbury in July at a size of approximately 32 mm standard length, and grew to approximately 61 mm by October. The downstream migration in the late summer and autumn appeared to be closely correlated with water temperature since movement reached a peak soon after the temperature in the Estuary had declined below 19° C, and ceased altogether below 9° C. Thereafter, there was virtually no movement of shad until temperatures rose sharply above 7° C in the spring. Maturing adult twaite shad were captured in late April and May as they moved into freshwater to spawn, probably in mid-June. Males were recorded slightly earlier during the migration and were generally younger than females. Furthermore, mean lengths and weights for individuals belonging to the different age classes indicated that males were also smaller. Logarithmic relationships between length and weight of young and adult A. fallax and for the variation with size in the number of rakers on the first gill arch are presented.     

Comparison of behavioral and physiological–biochemical indices in fingerlings of roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.) from the Ild River and Ild Bay in the Rybinsk Reservoir

It is found that the size–mass, physiological–biochemical, and behavioral parameters in roach fingerlings from the upper and lower (mouth) reaches of the Ild River differed during the autumn season. Compared with the roach from the upper reach of the river, the fingerlings of the same age from the mouth part have larger lengths and weights and a higher concentration of cations in the body. In experiments, the fish from the mouth part selected a lower (~4°C) temperature and showed a lower resistance to the water flow. The reason for differences in behavioral responses in two groups of juveniles of roach is probably, on the one hand, their physiological and biochemical characteristics and, on the other hand, the motivational component of fish behavior in different environments—hydrological, thermal, and hydrochemical conditions and different food items in geographically remote parts of the same river. It is assumed that in autumn roach fingerlings migrate from the littoral of the mouth part of the river into deeper parts under a decrease in water temperature before the downstream migration of the fingerlings in the rivers. This is probably due to the earlier achievement of the migration status of fingerlings from the mouth part than that in fish from the upper reach of the river and due to the peculiarities of their physiological state. Negative rheoreaction, manifested in the experiment in ~80% of the fish from the bay of the reservoir and ~55% of the fish from river, confirms the fish readiness to migrate and is likely due to the behavioral mechanism of fish migration from the littoral and downstream the river.     

A study of some acid hydrolases in the liver of the larval and adult lamprey

Summary The authors studied the behaviour of two acid hydrolases (phosphatase and proteinase) in the liver of the larval form (ammocoetes), of the starved larva, and of the adult lamprey (Lampetra zanandreai, Vladykov). In the homogenates of liver of ammocoetes in 0.25 M sucrose the enzymatic activities are largely sedimentable (phosphatase 67%; proteinase 56%). In the starved ammocoetes and in the adult lamprey the percentage of sedimentable activity gradually falls (phosphatase 46% and proteinase 52% in the starved ammocoetes; phosphatase 44% and proteinase 49% in the adult lamprey) whilst there is a corresponding gradual increase in free activity (phosphatase: from 24% in the normal ammocoetes to 39% in the starved ammocoetes and 50% in the adult lamprey; proteinase: from 25% in the normal ammocoetes to 35% in the starved ammocoetes and 54% in the adult lamprey). The action of detergent Triton X-100 causes an equal distribution of hydrolases activity in the three conditions of the liver.Only 25% of the sedimentable acid glycerophosphatase is accessible to the substrate in the ammocoetes, whilst in the starved ammocoetes and in the adult lamprey accessibility rises to 80%.The results we have discussed show that at metamorphosis and during fasting the lysosomes undergo such changes as to determine an actual intracellular release of the acid hydrolases studied.This work is dedicated to the memory of Prof. Giuseppe Zanandrea S. J., who greatly helped us with his advice.     

Patterns and some mechanisms of downstream migration of juvenile salmonids (with reference to the Utkholok and Kalkaveyem rivers in northwestern Kamchatka)

Principal patterns of the downstream migration of juvenile salmonids (Salmonidae) were discovered on the basis of data of three years of observations. It was found that the time of the beginning, the duration, and the scope of the downstream migration in each particular year are determined by a complex of environmental factors. The crucial abiotic factors are the temperature, the water level of the river, and the illumination. The biotic factors comprise the complex trophic factor. The abiotic environmental factors play the leading role in the realization of the downstream migration at the early ontogenetic stages. The role of the biotic environmental factors increases at the late ontogenetic stages. It was demonstrated that the juveniles that perform downstream migrations are a heterogeneous group consisting of fish of different species and specimens at different ontogenetic stages, of various sizes and ages, and those ready for the transition to the marine environment to variable degrees. The analysis of the patterns of the downstream migration allowed us to describe some mechanisms that control the realization of this process.     

Age and seasonal differences in the biometrics of dunlins (<Emphasis Type="Italic">Calidris alpina</Emphasis>) migrating in spring through the Pripyat River floodplain,southern Belarus

Analysis of the biometric parameters of dunlins is based on data of 496 adult birds and 214 birds in their second year of life captured during the spring migration in the years 2002–2014 in the floodplain of the Pripyat River in southern Belarus. The average size of the dunlins caught in this area shows that the majority of birds correspond to the parameters of the nominate subspecies (C. a. alpina). We have not found any statistically significant differences between the age groups in all morphometric parameters except for the length of the wing, which in the birds in their second year of life is slightly smaller than in adults. Both the adult dunlins and the yearlings have two peaks in the distribution of biometric parameters, such as the bill length to the nostril, the bill length to the feathering, the total length of the head with the bill, and the length of the wing, which is associated with differences in the size of males and females. We have noted an increase in the average bill length to the nostril, bill to feathering length, and the total length of the head with the bill, as well as the wing length in the adult birds captured during the spring migration. These values are especially significant in the last five days of May. The body mass index of the dunlins passing through the floodplain of the Pripyat River increases intensively during the migration, which can partly be attributed to the later migration of large birds (females). However, the main reason for the increase in the body mass index is that the birds migrating later in spring have higher energy reserves compared with the earlier migrants. At the end of the migration period, in the floodplain of the Pripyat River, the body mass indices of dunlins are very high. This suggests that birds leaving the stopover site in southern Belarus in early June have sufficient energy resources to reach the nesting places in one nonstop flight.     

Effect of environment on the adaptive abilities of fry roach Rutilus rutilus (L.) (Cyprinidae) during early ontogenesis

In recent years a considerable decrease in the abundance of predatory fishes has been observed in spawning tributaries of the Rybinsk Reservoir caused by their intensive catching. The lack of encounters with predators before the downstream migration of young fish hampers the development of necessary skills of defensive behavior in the absence of predation experience. As a result, after downstream migration, the juveniles are incapable of adapting to the predation pressure in the reservoir and are subjected to intensive elimination. The adaptive potential of the roach Rutilus rutilus L. was experimentally studied in siblings raised from the larvae to the late fry stage both in the presence and absence of a predator. It has been found that the fry that was raised under different conditions differed in their adaptive potential in new environment conditions.     

Development of seawater tolerance and subsequent downstream migration in wild and stocked young‐of‐the‐year derived Atlantic salmon Salmo salar smolts

This study investigated the development of hypo‐osmoregulatory capacity and timing of downstream migration in wild Atlantic salmon Salmo salar smolts from the River Stjørdalselva and stocked young‐of‐the‐year (YOY), derived S. salar smolts from the tributary River Dalåa. Both wild and stocked S. salar smolts developed seawater (SW) tolerance in early May, persisting through June, measured as their ability to regulate plasma osmolality and chloride following 24 h SW (salinity = 35) exposure. Although the majority of downstream migration among the stocked S. salar smolts occurred later than observed in their wild counterparts, the development of SW tolerance occurred concurrently. The wild S. salar from Stjørdalselva and stocked YOY smolts from the River Dalåa started to migrate on the same cumulative day‐degrees (D°). The study revealed no downstream migration before development of SW tolerance. This emphasizes the importance of incorporating physiological status when studying environmental triggers for downstream migration of S. salar smolts. Overall, these findings suggest that the onset of smolt migration in stocked S. salar smolts was within the smolt window from an osmoregulatory point of view.     

Selection and preference of benthic habitat by small and large ammocoetes of the least brook lamprey (<Emphasis Type="Italic">Lampetra aepyptera</Emphasis>)

In this laboratory study, we quantified substrate selection by small (<50 mm) and large (100–150 mm) ammocoetes of the least brook lamprey (Lampetra aepyptera). In aquaria, ammocoetes were given a choice to burrow into six equally-available substrate types: small gravel (2.360–4.750 mm), coarse sand (0.500–1.400 mm), fine sand (0.125–0.500 mm), organic substrate (approximately 70% decomposing leaves/stems and organic sediment particles, and 30% silt and fine sand), an even mixture of silt, clay, and fine sand, and silt/clay (<0.063 mm). Fine sand was selected with a significantly higher probability than any other substrate. Fine sand habitat is limited in many streams, in part owing to geology, but also as a result of channelization and excessive silt/clay sedimentation, which is a conservation concern. Our results indicate that ammocoetes of least brook lampreys are habitat specialists that prefer fine sand habitat. Hence, availability of fine sand habitat may limit distributions and population sizes.     

The effects of hatching date on timing of autumn migration in partial migrants – an individual approach

Timing of spring migration and breeding and their interaction with climate change has been widely studied in recent years, but the possible changes in timing of autumn migration have gained less attention. This work focuses on autumn migration and provides the first multi‐species individual‐based study of how hatching date affects the autumn migration date and migration age by using nestling ring data and re‐trappings of the same individuals during the autumn migration at the Hanko Bird Observatory, Finland. We studied three potentially multibrooded passerines (great tit, blue tit and coal tit) and two single‐brooded birds of prey (goshawk, sparrowhawk), all partially migratory short‐distance migrants. Individuals from late broods migrated at a younger age in all tit species and also in hawks the late hatched individuals tended to migrate at a younger age than the early‐hatched individuals. Late‐hatched individuals migrated later than early‐hatched individuals in blue and coal tits, where the latest hatchers represented second brood individuals. Based on our results, the time from hatching to autumn migration is not constant even among individuals of the same population. Our study indicates that climate warming induced advancement of avian breeding may cause changes in the timing of autumn migration through the frequency of second broods.     

Finish with a sprint: Evidence for time‐selected last leg of migration in a long‐distance migratory songbird

Under time‐selected migration, birds should choose a strategy for outcompeting rivals over securing access to prime resources at the final destination. Thus, migration can be viewed as a race among individuals where winners are arriving first when conditions are suitable. The sprint migration hypothesis predicts that individuals shift from maximum sustained speed to a final burst of sprint to shorten the transition from migration to breeding (Alerstam, 2006). In this study, we test the hypothesis of a final sprint migration in a long‐distance Afro‐Palearctic migrant, the collared flycatcher Ficedula albicollis, during autumn and spring, and compare migration strategies between the seasons. In both seasons, collared flycatchers evidently exhibited sprint migration by increasing their overall speed over the last leg of migration after the Sahara crossing. This phenomenon was more pronounced in spring, contributing to overall faster spring migration and possibly highlighting higher importance for early arrival at the breeding grounds. In both seasons and particularly in spring, late departing individuals flew at a faster rate, partially being able to catch up with their early departing conspecifics. Differential fueling strategies may play an important role in determining migration speed, especially during the early stages of the migration, and might explain the observed differences in migration speeds between late and early departing individuals. Our findings suggest competition for early arrival at the breeding and at the nonbreeding destinations alike. Sprint migration might be an appropriate strategy to gain advantage over conspecifics and settle in prime territories as well as to cope with the increasingly earlier springs at high latitudes.