Sea Lamprey Ammocoetes Research Articles

Riparian vegetation subsidizes sea lamprey ammocoetes in a nursery area

Fluxes of organic matter (OM) from terrestrial ecosystems subsidize stream food webs, which support the production of ecologically and economically important species such as the sea lamprey Petromyzon marinus. Debris have been previously observed in the gut contents of sea lamprey ammocoetes, but their origin and/or the nutritional sources assimilated are still poorly known. We used carbon (δ13C: 13C/12C) and nitrogen (δ15N: 15N/14N) stable isotopes to identify the main OM sources supporting the production of ammocoetes in a tributary of the Minho River (NW-Iberian Peninsula). Ammocoetes δ13C and C:N values increased with length. Smaller individuals likely assimilated more 13C- depleted sources such as fresh or decaying plant material. The increase in the C:N values with length suggests that ammocoetes accumulate lipids to support their metamorphosis and recruitment into an adult animal. Ammocoetes smaller than 30 mm presented an unusual variability for both δ15N and δ13C values, with values varying between 3.2‰ and 17.8‰ for δ15N and between − 38‰ and − 25.5‰ for δ13C in the same sampling site. This suggests that factors such as organic pollution inputs or time to the first feeding may have contributed to the observed variability. Detritus from the adjacent riparian vegetation was identified as the main food source assimilated by sea lamprey ammocoetes. The stable isotope mixing model (95% CI) indicates that the relative contribution of decaying riparian plants detritus varied between 38–59% and 55–73% at the end of the summer decreasing towards the end of the winter (2–34%). The relative contribution of other terrestrial-derived OM (i.e. fresh riparian detritus and particulate OM with terrestrial origin) was only relevant (> 40%) at the end of the winter. This study shows that there is a strong connectivity between the stream food web and the adjacent riparian ecosystem, and that protection of both riparian and catchment forest cover are essential to preserve terrestrial-aquatic linkages which can support the development of sea lamprey ammocoetes.

Muscle fatty acid profiles of sea lamprey (Petromyzon marinus L.) indicate the use of fast metabolized energy during ontogenesis.

A comprehensive characterization of muscle's FA composition of sea lamprey ammocoetes and adults was performed to test the hypothesis that larvae, and early spawning migrants have a similar FA profile prior to metamorphosis and to spawning migration. Subsequently, the role played by FA signature in these two highly demanding stages of life cycle was inferred. The results confirm that muscle represents an important fat reservoir, and the FA trophic markers revealed the importance of bacteria as sources of iso and anteiso FA and the strong trophic representation of benthic phytoplankton (diatoms) to larvae muscle FA profile. In early spawning migrants, the significance of marine food web to FA muscle profile is highlighted by the presence of FA signatures characteristics of herbivorous calanoid copepods. Although both life cycle phases studied do not share the same muscle FA signature, there is a part of the profile that is common, which is characterized by FA used in β-oxidation, such as C18:1ω9 but also by medium chain FA and PUFA which points that PUFA are spared as fuel to β-oxidation process and probably used to the development of tissues membranes (ammocoetes) and gonadal development and eicosanoid production among others (early spawning migrants). Further studies on FA profile are necessary to elucidate the FA role either during different life stages (ontogeny) or in the distinct habitats frequented (freshwater versus marine) by this diadromous species.

Demography of sea lamprey (Petromyzon marinus) ammocoete populations in relation to potential spawning‐migration obstructions

Abstract Recent advances in the understanding of lamprey migrations have led to concerns over the impacts of obstructions on the demography of many species. This study investigated sea lamprey (Petromyzon marinus) larvae (ammocoetes) in two adjacent but contrasting rivers, both designated Special Areas of Conservation under the EC Habitats Directive (92/43/EEC), one (the River Wye) with a small number of potential migration obstructions in its upper reaches and one (the River Usk) with obstacles along its course. The geographical distributions, densities and age structures of the ammocoete populations were examined in relation to the locations of potential obstructions to the spawning migrations of anadromous adults. A minimum of three age classes was recorded as far as 200 km upstream of the mouth of the River Wye (93% of the length of the mainstem), demonstrating that adults regularly migrate to the upper reaches of the catchment (downstream of a natural waterfall). By contrast, sea lamprey ammocoetes appeared to be absent (in suitable habitat) from 20 km (17%) of the River Usk, and there was a reduction in density, prevalence and the number of age classes upstream of two putative spawning‐migration obstructions. This study highlights some of the potential impacts of habitat fragmentation by obstructions on the spawning migrations of anadromous species, as inferred from ammocoete demography. When used in combination to compare contiguous reaches, ammocoete densities, prevalence and age structure may be a useful indicator of which structures are likely to be important migration obstructions, and where further studies or mitigation efforts should be focused. It is likely that passage past some obstructions is enhanced if high river levels occur during the spawning migration, but there is a need to facilitate passage during all conditions, to improve access to under‐exploited spawning and nursery areas.

Morphological analysis of geographic variation of sea lamprey ammocoetes in Portuguese river basins

The main objective of this study was to compare the morphological variability of sea lamprey (Petromyzon marinus L.) larvae from the main Portuguese river basins. Samples were collected in rivers Minho, Lima, Cavado, Vouga, Mondego, Tejo and Guadiana. Specimens were analysed in terms of morphometric (linear body measures) and meristic (number of myomeres) characters to investigate the hypothesis of population fragmentation between river basins caused by some degree of homing behaviour. The discriminant analysis showed a morphological segregation of the studied populations based on the characters head, tail and branchial length. The discriminatory power of the meristic characters was comparatively weaker, with the number of trunk myomeres, and to some extent the head myomeres, being responsible for the reduced separation between groups. Both analyses were consistent in identifying the cephalic region as the most important morphological feature to discriminate populations of sea lamprey larvae in the Portuguese territory. The largest cephalic region of the ammocoetes sampled in the northern river basins may be responsible for a better feeding efficiency and, consequently, higher values of condition factor.

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.

Distribution, larval stage duration and growth of the sea lamprey ammocoetes, Petromyzon marinus L., in a highly modified river basin

Abstract – Larval stage duration of the sea lamprey, Petromyzon marinus, in the River Mondego is estimated to last for 4 years. The number of annuli provides reliable age estimates when compared with length–frequency distributions analysis. The growth rate of the sea lamprey ammocoetes displays strong seasonal patterns, and reaches its highest value during the first 2 years of larval stage. About 69% of the length increment between hatching and metamorphosis is attained at the end of the second year. There is a longitudinal gradient associated with ammocoete distribution along the river. Relative abundance of ammocoetes decreases downstream from the Açude‐Ponte dam, the first obstruction encountered by the adult sea lampreys in their upstream spawning migration along the River Mondego.

Toxicity of TFM Lampricide to Early Life Stages of Walleye

Abstract We studied the effects of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) on gametes, newly fertilized eggs, eyed eggs, larvae, and swim-up fry of the walleye Stizostedion vitreum. When gametes from sexually mature walleyes were stripped into solutions of TFM, no effects were observed during the fertilization process at concentrations up to 3.0 mg/L—three times the concentration lethal to 99.9% of larval sea lampreys Petromyzon marinus held 12 h (LC99.9) under the same test conditions. Newly fertilized eggs likewise were unaffected during water hardening by concentrations of TFM that were lethal to sea lamprey ammocoetes. Eyed eggs, sac fry, and swim-up fry yielded LC25 values that were 2.5 to 5 times greater than the 12-h LC99.9 for sea lamprey ammocoetes. The data thus indicated that all of the early life stages of walleyes tested were considerably more resistant than sea lamprey ammocoetes to TFM, and that it is unlikely they would be adversely affected by standard stream treatments to ki...

Use of Calcareous Otic Elements (Statoliths) to Determine Age of Sea Lamprey Ammocoetes (Petromyzon marinus)

I examined the possibility that the number of internal bands in calcareous otic elements (statoliths) of sea lamprey ammocoetes (Petromyzon marinus) could be used to estimate age. The correspondence between statolith band number and known ammocoete age was very close for the first 4 yr but less rigorous for the few 7-yr-old specimens examined. This is the first use of calcareous otic elements to determine age in a nonteleost and represents the only direct age determination technique for lampreys. Compared with length–frequency analysis, this method will provide greater reliability of age determinations, essential for investigations on the life history and ecology of sea lampreys.

Problems with Samples of Sea Lamprey (Petromyzon marinus) Ammocoetes Used in Stock Identification Studies

Allelic variation in sea lamprey (Petromyzon marinus) ammocoetes from the Lake Huron, Lake Michigan, and Lake Superior drainage basins was studied by starch gel electrophoresis. Previously untried enzyme systems were examined in sea lamprey ammocoetes. No new polymorphic enzyme systems were found. The allelic frequencies of ammocoete samples frequently failed to conform to Hardy–Weinberg equilibrium values. Allelic frequency variation observed among samples from the same drainage was larger than the variation observed among drainages. The results of this study and field observations suggest that the effective size of spawning groups that contribute progeny to samples is often small. These factors make ammocoete samples undesirable for use in stock identification studies.

Changes in Spawning Runs of Sea Lamprey (Petromyzon marinus) in Selected Streams of Lake Superior after Chemical Control

During lampricide treatment of a stream, sea lamprey, Petromyzon marinus, that will constitute the spawning run the following spring inhabit the Great Lakes and are not affected by the treatment. However, the number of adults captured at electrical barriers declined as much as 99% in some streams 1 year after chemical treatment. Large declines of adults were noted in streams which were treated late in the year. Streams in which significant populations of larval lampreys survived the chemical treatment, or contained lentic populations, continued to attract adults. Adult sea lampreys could be attracted to sea lamprey ammocoetes in streams or in offshore areas and hence use this as one of a number of clues to determine rivers suitable for spawning.Key words: sea lamprey, olfaction, orientation/homing, spawning migration, habitat alteration (chemical), Petromyzon marinus, lampricides

Role of glucuronide formation in the selective toxicity of 3-trifluoromethyl-4-nitrophenol (TFM) for the sea lamprey: comparative aspects of TFM uptake and conjugation in sea lamprey and rainbow trout

This report is concerned with the comparative aspects of disposition and conjugation of 3-trifluoromethyl-4-nitrophenol (TFM), a selective sea lamprey larvicide in sea lamprey ( Petromyzon marinus) and rainbow trout ( Salmo gairdneri). When exposed to identical water concentrations of TFM, sea lamprey ammocoetes exhibited a higher rate of accumulation and an increased steady-state level of TFM compared to trout. Regardless of the life stage of sea lamprey or size of trout studied, sea lamprey revealed a higher concentration of free TFM in blood and tissues. The higher concentration of TFM in lamprey blood was demonstrated at a variety of water concentrations of TFM. In vitro glucuronyl transferase assays demonstrated that the sea lamprey had a lower rate of formation of TFM glucuronide when compared to trout. In vivo, sea lamprey exhibited a much higher ratio of free to conjugated TFM than trout. Pretreatment of sea lamprey and trout with salicylamide, an inhibitor of glucuronyl transferase, shifted the LC 50 for trout from 9.7 mg/liter to 3.6 mg/liter and did not alter the LC 50 for sea lamprey.