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This study examines the sediment preferences of small sandeel (Ammodytes tobianus), an elongated forage fish common in marine and brackish environments of northern Europe. Sandeel have a high fidelity for sandy habitats and spend much of their lives buried, as an important part of both their diel behavioural cycles and overwintering behaviour. A series of independent choice laboratory assays were conducted using wild-caught schools of small sandeel, to: (1) determine their preferred substrate composition for burial; (2) identify the upper limits of sediment grain-sizes that may be utilised for burial, and; (3) investigate the effects of light intensity on burial behaviour. Initial experiments found a clear preference for burial within sediments composed of coarse sand and fine gravel (0.5–4.0 mm) but showed at least some utilisation of both coarser and finer sediment compositions. In further trials, burial was found to be almost entirely eliminated in sediments that contained significant gravel components >4.0 mm. Light manipulation experiments also showed that light intensity was an important factor that influences their choice of burial area. This study is the first to experimentally investigate the sediment preferences and grain-size tolerance limits of small sandeel. These results specifically highlight how subtle differences in both sediment composition and light may influence the habitat usage of small sandeel, which may be valuable for understanding their distribution in the wild and to inform future management and conservation for the species. • Investigated sediment preferences for small sandeel (Ammodytes tobianus). • Preferred substrate is coarse sand and fine gravel, but avoidance are observed when exposed to larger gravels of pebbles. • Initial findings of light gradients that influence sandeel burial behaviour are reported. • Results provide insights for understanding sandeel behaviour, ecology, and distribution in the wild. • A multinomial modelling approach is introduced to enhance data interpretation and address uncertainties for experimental studies. [ABSTRACT FROM AUTHOR]

In the food bolus of small sandeel Ammodytes tobianus caught on the littoral of the Baltic Sea in the area of the Curonian Spit, two types of microplastic material were found—film and villus fibers. Microplastic was found in 21% of the studied individuals, and its portion is <0.01% of the mass of food. Microplastic film is defined with use of infrared spectra as polypropylene in the stage of destruction. [ABSTRACT FROM AUTHOR]

Sandeel partly spend their life buried in the sediment, without a permanent burrow opening or an inhalant opening in the sediment. We linked the presence of three sandeel species ( Ammodytes tobianus , A. marinus and Hyperoplus lanceolatus ) off the southern Dutch coast of the North Sea to sediment related environmental variables; (1) sediment composition, with a hypothesized preference for low silt content and high medium-coarse sand content, (2) water velocity near the seabed, with a hypothesized preference for high water velocity and (3) fishing effort of the beam trawl fleet targeting flatfish and shrimp, with a hypothesized negative impact of fishing on sandeel presence. Data originated from an intensive benthic sampling scheme, VMS and logbook databases and a hydrodynamic model. Statistical models were run including these environmental variables plus year, depth, water temperature and salinity. Sandeel presence was negatively correlated with flatfish and shrimp fisheries – both Ammodytes species with flatfish fisheries and H. lanceolatus with shrimp fisheries. Water velocity and silt content were correlated as hypothesized with the presence of all species, and sand content was positively correlated with both Ammodytes species. The remaining environmental variables also showed a significant relation with at least two sandeel species. These findings agree with and greatly expand on previous studies on the relation between sandeel and its environment. [ABSTRACT FROM AUTHOR]

Passive integrated transponder (PIT) tags are commonly used to assess fish movement for use in fisheries management. Here, we investigated physiological and behavioral effects of tagging on sandeels ( Ammodytes tobianus) using PIT tags constituting 2.1 ± 0.9% of their body weight. Swimming stamina ( RSS ), calculated as time spent swimming against the current relative to total swimming time, and tail beat frequency were compared between tagged and untagged fish as was blood hematocrit levels at 7, 14, and 42 d post-tagging. Survival and tag retention were also documented at 14, 42, and 84 d (via x-rays and dissections). RSS was not different between tagged and untagged fish with means (± SD) of 60 ± 9% and 61 ± 12%. Tail beat frequency was not different between tagged and untagged fish at 2.8 ± 0.3 and 3.0 ± 0.4 beats s −1 for tagged and untagged fish, respectively. Likewise, hematocrit was not affected by tagging and levels were between 21–26% for both groups. Survival rates were high and did not differ between groups (96% for tagged and 99% untagged fish). Tag retention was 100%. X-rays and dissections did not reveal any signs of tag movement at 14–84 d, and there was no difference between relative positions of the tags. None of the tags were encapsulated in the body cavity after 14 d, whereas 40 and 56% of the tags were encapsulated in a thin tissue membrane between the intestine and kidney after 42 and 84 d, respectively. After 14 d all incisions had healed with only minor or no signs of the tag insertion site. Collectively, these data provide substantial evidence for the possibility of conducting large-scale tagging studies on this species in the field. [ABSTRACT FROM AUTHOR]

Background. The small sandeel, Ammodytes tobianus L., is a fish species of no commercial value, which is probably why its biology and, particularly, taxonomic status has not attracted much interest. However, the ecological importance of this species outweighs its economic value. It has been regarded a "vulnerable" fish species and therefore its taxonomic status urgently needs more detailed studies. The presently reported study was intended to be a contribution to the knowledge on poorly known morphology of this fish, from a single location in the southern Baltic Sea. Materials and methods. The fish (130 specimens, 9.2-16.3 cm TL) were collected in June 1995 from the area between the Puck Bay and open waters of the Gulf of Gdańsk, at the depth of 8 m. Taxonomic analysis involved both meristic and morphometric characters. The lengths were expressed as percentage of the standard length (SL) of the fish while the fish head characters-as percentage of the head length (HL). In addition, the coefficients of correlation and determination (r and r2, respectively) were calculated for the relations between all characters studied and standard length (SL) and for the relations between the characters pertinent to head and the head length (HL) in the sample examined. The fish age was determined from the otoliths. Results. The age of fish examined ranged from 1+ to 4+, and the sandeels aged 2+ were the distinctly dominant age group. The most abundant size group was the 13.0-13.99 cm length class. The coefficients of variation in the meristic characters were relatively low. The vertebral count and the number of plicae were the most stable characters in the sample studied, while the anal- and pectoral fin ray counts proved to be the most variable ones. Meristic characters can be described by the formula: D (47-49) 50-55, P (10) 11-12 (13), A (24, 25) 26-30 (31), sp.br. (21) 22-27 (28), vt. 61-67 (68). The morphometric relations showed a tendency to allometry, only the postdorsal and postorbital distances showed almost the isometric pattern of growth. The head characters expressed as proportion of the head length showed a very low variability. The strongest negative relations, on the course of exponential curve, were recorded in the following characters: (first) depth of head, eye diameters, jaws length, interorbital distance (associated with the head length); (second) predorsal distance (associated with the fin arrangement), minimum and maximum body depths and length of caudal fin (the features associated with the body shape). Conclusion. The mean vertebral count obtained in the present study indicates the sampled sandeel from the Gulf of Gdańsk to belong to the autumn-spawning component of the stock. The sandeel is a species of relatively short lifespan, the age group IV was the oldest one and the least numerous in the sample (3.38% of the all specimens). The head length and pectoral fin rays count may be regarded as the characters differentiating the Baltic and Atlantic populations, however more detailed study from different areas of the Baltic Sea is urgently needed to confirm this assumption.

Accurate stock assessments for each of the dominant species of sand lances in the northeast Atlantic Ocean and adjacent areas are not available due to the lack of a reliable identification procedure; therefore, appropriate measures of fisheries management or conservation of sand lances cannot be implemented. In this study, detailed morphological and molecular features are assessed to discriminate between four species of sand lances belonging to the genera Ammodytes and Hyperoplus. Morphological characters described by earlier authors as useful for identification of the genera are confirmed, and two additional distinguishing characters are added. A combination of the following morphological characters is recommended to distinguish between the genera Hyperoplus and Ammodytes: the protrusibility of the premaxillae, the presence of hooked ends of the prevomer, the number of dermal plicae, and the pectoral-fin length as a percentage of the standard length. The discriminant function analysis revealed that morphometric data are not very useful to distinguish the species of each of the two genera. The following meristic characters improve the separation of H. lanceolatus from H. immaculatus: the number of lower arch gill rakers, total number of gill rakers, numbers of caudal vertebrae and total vertebrae, and numbers of dorsal-fin and anal-fin rays. It is confirmed that A. tobianus differs from A. marinus by its belly scales that are organised in tight chevrons, scales which are present over the musculature at the base of the caudal fin, as well as by the lower numbers of dermal plicae, dorsal-fin rays, and total vertebrae. In contrast to the morphological data, mitochondrial COI sequences (DNA barcodes) failed to separate unambiguously the four investigated species. Ammodytes tobianus and H. lanceolatus showed an overlap between intraspecific and interspecific K2P genetic distances and cannot be reliably distinguished using the common DNA barcoding approach. Ammodytes marinus and H. immaculatus exhibited gaps between intraspecific and interspecific K2P distances of 2.73 and 3.34% respectively, indicating that their DNA barcodes can be used for species identification. As an alternative, short nuclear Rhodopsin sequences were analysed and one diagnostic character was found for each of the species A. marinus, H. lanceolatus, and H. immaculatus. Ammodytes tobianus can be characterised by the lack of species-specific mutations when compared to the other three species. In contrast to COI, the short nuclear sequences represent a useful alternative for rapid species identification whenever an examination of morphological characters is not available. [ABSTRACT FROM AUTHOR]

Knowledge of life history and connectivity between essential ecological habitats are relevant for conservation and management of species and some natural tracers could be used to study the lifecycles of small or short-lived marine fishes. Although sandeels are central in marine food webs and are key species, there is incomplete knowledge about population mixing and migration patterns. For the first time the use of the otolith microchemistry on sandeel species is evaluated in the case of the Small Sandeel. Variations in microchemical fingerprints of 13 trace elements are performed with a Femtosecond LA-ICPM from the core to the margin of sagittal otolith and are compared within and between otoliths extracted from 34 fishes sampled in three different sites along the coast of the south-western English Channel in France. Firstly, preliminary investigations on the validity of the method revealed that Mg/Ca was the only ratio significantly dependant on fish ontogeny and sampling season. Secondly, the Mn/Ca, Zn/Ca, and Cu/Ca ratios enabled us to significantly discriminate among sampling sites. Thirdly, microchemical fingerprints of each life stage varied significantly among sampling sites but not within them, suggesting high site fidelity over relatively short distances. Finally, the fingerprints of all life stages were significantly different from those of the larval and metamorphosis stages. The otolith microchemistry could detect change of signature relative to the shift from a pelagic behaviour to a resident bentho-pelagic behaviour during the middle of the juvenile stage in Small Sandeels. Hence, analysis of trace element fingerprints in otoliths appears to be a valuable method to further studies on ontogenic habitat change, population mixing and variation of life history and be helpful for the management at local or regional scales of short-lived species such as those belonging to other Ammodytidae. [ABSTRACT FROM AUTHOR]

Effects of water salinity (3.0-9.0 PSU) on the duration and outcome of embryogenesis in the lesser sandeel ( Ammodytes tobianus (L.) as well as on survival, size, and malformation rate of the newly hatched larvae were followed, based on observations involving equipment consisting of a microscope and still and digital cameras. The images obtained and measurements of egg and larval dimensions were analyzed using the NIS elements Br. computer software package. The lowest salinity tested (3.0 PSU), similar to that in the inshore Baltic Sea waters native for the species studied, produced a lower fertilization rate and resulted in extended embryogenesis, reduced embryo survival, changes in the hatch size, and increased larval malformation rate. The high-end salinity (7.5-9.0 PSU), higher than that prevailing in the species's spawning grounds in the Baltic Sea, resulted - similarly to the low-end salinity - in disturbed development and growth of the embryos. [ABSTRACT FROM AUTHOR]

The parameter values of a generic model of gastric evacuation were estimated from evacuation data on Atlantic cod Gadus morhua fed meals of four fish prey: herring Clupea harengus, sprat Sprattus sprattus, lesser sandeel Ammodytes tobianus and dab Limanda limanda. The effects on evacuation of photoperiod and pre-experimental treatment of prey were also tested. Freshly killed A. tobianus were evacuated from the stomach of G. morhua at a rate similar to the value estimated from conspecifics kept deep-frozen and subsequently thawed prior to the evacuation experiment. The evacuation rate in G. morhua exposed to continuous light did not differ from the rate obtained from fish maintained under a 12L:12D photoperiod. The evacuation rates estimated from the latter fish in the dark and light periods, respectively, were likewise similar. These results indicate that the resistance of prey to the digestive processes is not altered significantly by the pre-experimental treatment of prey and that there is no diurnal variation per se in the rate of evacuation for G. morhua. Therefore, it is believed that the present parameterization of the evacuation model should prove especially useful for studying the role of G. morhua as a top predator in natural systems. [ABSTRACT FROM AUTHOR]

The simple surface abstraction of the cylinder model (each prey as well as the total stomach contents is considered a cylinder that is gradually reduced by successive peeling off its curved side) was challenged by data on evacuation of a meal composed of three sandeels Ammodytes tobianus and a dab Limanda limanda fed to Atlantic cod Gadus morhua. While the body shape of A. tobianus comes close to that of a cylinder, the flatfish L. limanda takes a discoid form. As opposed to a modified form of the cylinder model, where the contrasting geometries of the fish prey were implemented, the simple, original cylinder model held the potential to predict evacuation of the individual prey types as well as the total stomach contents. Thus, the present study adds significantly to the increasing evidence that points to the generic nature of the model and its implicit square root function. Also, the present study corroborated a basic assumption that the variability of evacuation data not accounted for by the cylinder model primarily can be ascribed to the intraspecific variation in gastric performance of the predator. [ABSTRACT FROM AUTHOR]

The influence of prolonged moderate ( c. 60% oxygen saturation) and severe hypoxia ( c. 35% oxygen saturation) on the diurnal activity pattern of sandeel Ammodytes tobianus was examined. In moderate hypoxia, the emerging and burying rates were significantly higher compared to that in normoxia, whereas fewer fish ( c. 10%) were present in the water column. In contrast, severe hypoxia resulted in twice as many or more fish being present in the water column compared to that in normoxia. The increased number of swimming fish was not just a relative change due to an effect from hypoxia treatment, but the behaviour of the fish was also changed. The summed activity (emerging plus burying events) was lower in severe hypoxia compared to normoxia except during hours of dim light. All fish were buried during night-time, regardless of treatment, with the exception of some in severe hypoxia during the first couple of hours of darkness. [ABSTRACT FROM AUTHOR]

Starting in 1980s, the inner Danish waters have yearly been exposed to seasonal oxygen deficiency (hypoxia). Through spatial–temporal interpolation of monitoring data (1998–2005), we investigated oxygen deficiency impacts on suitable burying habitats for lesser sandeel (Ammodytes tobianus). Furthermore, the consequences of a predicted 4 °C temperature increase within this century were investigated. Maps of bottom oxygen deficiency (oxygen saturation ≤ Scrit of sandeel) were overlaid on maps of sediment composition. Throughout the study period (1998–2005), about 8% of the suitable sediments were affected by oxygen deficiency during an average year and 23% in the most severe year. Regional differences underlay the interannual variations. The extent of oxygen deficiency in enclosed regions varied from 20% to 33% of the suitable seabed being affected, whereas in open-water regions oxygen deficiency problems were limited during average years. However, large areas of the open-water seabed experienced oxygen deficiency during severe years. In such years, under a 4.0 °C temperature increase scenario, the extent of oxygen deficiency on open-water suitable patches was predicted to increase from 25% to about 40%. [ABSTRACT FROM AUTHOR]

The observations that the gastric evacuation of a meal was accelerated after ingestion of an additional meal, whereas the evacuation of the latter meal was slowed down were compared to the predictions of mass-dependent models derived from experiments on evacuation of single meals. In contrast, the present study on cod Gadus morhua fed identical double meals of sandeel Ammodytes tobianus demonstrated that the evacuation of each meal was slowed down relative to the evacuation of a single meal. This fact could be explained by the exposed meal surface area being reduced while the meals were together in the stomach as it was expected by a surface-dependent cylinder interpretation of the square-root model. The cylinder model forecasted accurately the observed evacuation of each meal in the double-meal situation. The simple surface considerations of the model further explained the discrepancies between observed and expected evacuation rates using mass-dependent models, which suggested that the above finding of the previous studies was an artefact. The ability of the cylinder model to predict properly also the evacuation of multiple meals in juvenile coho salmon Oncorhynchus kisutch indicated that the model would apply to gastric evacuation in small-sized predatory fishes as well. This should increase considerably its value as a generic tool for studies on the feeding biology of fishes in the wild. [ABSTRACT FROM AUTHOR]

Lesser sandeel ( Ammodytes tobianus) is abundant in near-shore areas where it is a key prey. It exhibits the behaviour of alternating between swimming in schools and lying buried in the sediment. We first determined the species’ standard metabolic rate (SMR), critical partial pressure of oxygen $$(P_{{\rm O}_{2{\rm crit}}})$$ and maximal oxygen uptake $$(M_{{\rm O}_{2{\rm max}}}).$$ The sandeel were then exposed to an acute stepwise decline in water oxygen pressure (18.4, 13.8, 9.8, 7.5, 5.8, 4.0, and 3.1 kPa $$P_{{\rm O}_{2}}$$ ). Swimming speed and routine- and post-experimental blood lactate levels were measured, in addition to levels associated with strenuous exercise. The SMR was 69.0 ± 8.4 mg O2 kg−1 h−1 and the $$M_{{\rm O}_{2{\rm max}}}$$ about seven times as high. The $$P_{{\rm O}_{2{\rm crit}}}$$ was found to be 4.1 kPa. A rapid decrease (within 1 h) in $$P_{{\rm O}_{2}}$$ from 18.4 to 3.1 kPa had no significant effect on routine swimming speed (0.9 ± 0.06 bl s−1), but steady levels at the lowest $$P_{{\rm O}_{2}}$$ (3.1 kPa) gradually reduced the swimming speed by 95% after 40 min. The routine blood lactate levels were 2.2 ± 0.6 mmol l−1, while the levels in the strenuously exercised groups were significantly higher with 5.4 ± 1.6 and 5.8 ± 1.3 mmol l−1. The highest levels were observed in post-experimental fish with 7.5 ± 2.7 mmol l−1. We argue that, as sandeel showed no decrease in swimming speed (to offset stress) nor an increased speed to escape the hypoxia, the fish either rely on a low SMR and being a reasonable strong oxygen regulator $$(\hbox{low}\;P_{{\rm O}_{2{\rm crit}}})$$ as a mean to cope when exposed to acute hypoxia, or that the hypoxia simply developed too fast for the fish to decide on an appropriate strategy. Not showing a behavioural response may in the present case be maladaptive, as the consequence was major physiological stress which the fish however appears tolerant towards. The high routine blood lactate levels suggest that anaerobic metabolism is associated with swimming in sandeel, which may be related to the specific lifestyle of the fish where they regularly bury in the sediment. [ABSTRACT FROM AUTHOR]

The oxygen environment around buried sandeels (Ammodytes tobianus) was monitored by planar optodes. The oxygen penetration depth at the sediment interface was only a few mm. Thus fish, typically buried at 1-4 cm depth, were generally in anoxic sediment. However, they induced an advective transport through the permeable interstice and formed an inverted cone of porewater with 93% air saturation in front of the mouth. From dye experiments the mean ventilatory flow rate was estimated at 0.26±0.02 ml min-1 (86.9±7.3 ml min-1 kg-1) (N=3). Expelled water from the gills induced a 1 cm circular plume with <15% air saturation around the gills. During this quasi-steady ventilation mode, fish extracted 86.2±4.8% (N=7) of the oxygen from the inspired water. However, 13% of the investigated fish (2 of 15) occasionally wriggled their bodies and thereby transported almost fully air-saturated water down along the body, referred to as 'plume ventilation'. Yet, within ~30 min the oxic plume was replenished by oxygen-depleted water from the gills. The potential for cutaneous respiration by the buried fish was thus of no quantitative importance. Calculations derived by three independent methods (each with N=3) revealed that the oxygen uptake of sandeel buried for 6-7 h was 40-50% of previous estimates on resting respirometry of non-buried fish, indicating lower O2 requirements during burial on a diurnal timescale. Buried fish exposed to decreasing oxygen tensions gradually approached the sediment surface, but remained in the sediment until the inspired water reached 5-10% air saturation. [ABSTRACT FROM AUTHOR]

Studies helminth communities of the lesser sandeels (Ammodytes tobianus) by researchers from Galway, Ireland. Examination on the sandeels infected with helminth parasite species; Investigation on the relationship between spawned groups, host length and season versus the abundance; Assessment on the role of A. tobianus as an intermediate host for helminths.

The accumulation of polychlorinated biphenyls (PCBs), DDTs (p,p'-DDT [1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane], o,p'-DDT [1,1,1-trichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane], p,p'-DDD [1,1-dichloro-2,2-bis(4-chlorophenyl)ethane], o,p'-DDD [1,1-dichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane], and p,p'-DDE [1,1-dichloro-2,2-bis(4-chlorophenyl)ethene]), chlordanes (trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor and oxychlordane), hexachlorocyclohexanes (α-, β-, and upsih;-isomers), hexachlorobenzene, and mirex was investigated in a marine food web from southeastern Norway. The food web consisted of the polychaete Nereis diversicolor, lesser sandeel (Ammodytes tobianus), three species of gobys (Gobiusculus flavescens, Pomatoschistus sp., and Gobius niger), bullrout (Myoxocephalus scorpius), cod (Gadus morhua), herring gull (Larus argentatus), and harbor seal (Phoca vitulina). The results show that interspecies differences in organochlorine (OC) compositional patterns in the food web depend on several factors (allometric, biochemical, physical, and physicochemical) specific to both the chemicals and the organisms. The importance of dietary accumulation and metabolic capacity increases toward higher trophic levels, while the OC patterns are to a larger extent determined by the lipophilicity and water solubility of the compounds at lower trophic levels. Furthermore, stable nitrogen isotopes provided a continuous measure of trophic position, rendering us capable of quantifying the increases in the concentrations of ΣPCB, Σdichorodiphenyltrichloroethane (DDT), and Σchlordane (CHL) and the percentages of highly chlorinated PCBs through the food web. The information provided may be important for future modeling of the fate of organochlorine contaminants in marine food webs. [ABSTRACT FROM AUTHOR]