Effect of food availability on the growth and age determination of European sardine (Sardina pilchardus Walbaum, 1792) larvae

Accurate assessment of age and growth of fish is essential to understand population dynamics, namely for age-structured stock assessment and for determining vital rates of fish (e.g. age at sexual maturity) and their relationship with environmental variability. To validate the daily deposition in the otoliths of European sardine (Sardina pilchardus) larvae, these were reared with a range of food densities translating into feeding rates extending from less than required for maintenance to saturated feeding levels. When exogenous feeding began, a high variability in the relationship between number of growth increments (GI) and elapsed days after hatching (dph) was observed, irrespective of the feeding treatment. GI counts using a light microscope were less than one per day for larvae <15 dph (ranging from 0.17–0.43 GI day−1) and similar for larvae reared with different food concentrations. The rate of GI count vs age was significantly higher for larvae older than 15 dph. GI count from 3–30 dph was lower than one per day (0.45–0.75 GI day−1 95% CI) for fed larvae 3–30 dph. Scanning electron microscopy confirmed the daily deposition of GI and revealed some increment widths around 0.2 μm, particularly during the first week post-hatch. Otoliths of wild sardine larvae exhibited narrow GI (<0.5 μm) comparable with reared larvae. This study demonstrates that during the first weeks after hatch the daily increment deposition is underestimated using traditional light microscopy, which must be taken into account in future works determining wild sardine larval growth.

How old are giant squids? First approach to aging Architeuthis beaks

The giant squid Architeuthis dux Steenstrup, 1857 is one of the largest and most enigmatic marine species. Its age estimation remains controversial with many estimates of maximum age ranging from 1 to 14 yrs. Successful results regarding the study of aging in cephalopod beaks for some octopod and oegopsid squids support using these structures for age estimation. We analyzed the beaks of 10 individuals, caught between 1995 and 2006, with reconstructed dorsal mantle lengths (DMLs) between 823 and 1418 mm. The beaks were measured and weighed, and their microstructure was analyzed in three ways: (1) in the rostrum area [rostrum sagittal sections (RSS)] for both upper and lower jaws, and the (2) inner lateral wall surfaces (LWS) and (3) inner crest surfaces (CS) for upper jaws. A constant sequence of increments was observed along the RSS, indicating that the use of lower jaws is more feasible due to the higher erosion and tighter packing of increments of upper jaws. The statolith of one individual was analyzed, resulting in 520 increments (579 increments from RSS of its lower jaw). Assuming daily deposition, the age estimations in RSS between 411 and 674 d suggest rapid growth of A. dux, averaging 1.97 mm DML d–1 (SD 0.45). When maximum ages were estimated by applying these results to the largest measured specimens in the literature (e.g., 2400 mm DML), an age of approximately 3 yrs was obtained. Analysis over a greater size range of individuals would allow more accurate age estimations of this emblematic squid.

Microstructure of the otoliths of the glacier lanternfish, Benthosema glaciale

Ageing using otolith microstructure is based on the assumption that growth increments are deposited daily. Individuals of the glacier lanternfish (Benthosema glaciale) were collected in the Flemish Cap (north-west Atlantic) during June–July 2010. A total of 44 individuals (ranging from 28 to 49mm standard length; <2 years old) were selected to analyse otolith microstructure using light microscopy in order to assess the reliability of the use of microincrements to infer the true age of this species. Three distinct zones were distinguished: the larval zone, the postlarval zone and the postmetamorphic zone. The otolith core was, on average, 8±0.7μm. The mean microincrement number in the larval zone was 42±7.5 within a radius of 0.095±0.010mm whereas in the postlarval zone it was 25±3.0 within a segment of 0.104±0.015mm. SEM examinations in a subsample of otoliths showed that the resolution power of the light microscope was sufficient to study both the larval and the postlarval zones. Back-calculation from the time of capture suggests a hatching period from mid-June to mid-December with a peak in September. The spawning time and daily deposition of the microincrements in B. glaciale are discussed.

DEPOSITION OF PETROLEUM HYDROCARBONS WITH SEDIMENT TRAPPED IN SNOW IN ROADSIDE AREAS

Total petroleum hydrocarbon (TPH) deposition rates were determined along various roads using the natural snow cover as deposition trap. Daily deposition rates decreased with distance from the roads, which coincided with long-term TPH accumulation in roadside soils. Scanning electron microscopy (SEM-EDX) of the snow meltwater sediment revealed occurrence of carbon-rich plaques, which were identified as hydrocarbons using FTIR-microscopy. GC-MS revealed that the compounds extracted from the sediment consisted of an unresolved complex hydrocarbon mixture (UCM). Individual n-alkanes could not be resolved in the sediment extract, whereas TPHs extracted from soils contained a series of n-alkanes peaking at C25-C27. The proportion of UCM compounds from TPHs decreased with distance from road. We conclude that high-boiling hydrocarbons bind to coarse mineral dust and/or to splash water and vehicle spray, which preferentially deposit within a 10 m roadside strip.

Female reproductive biology, and age of deep-sea squid Histioteuthis miranda from southern Africa

Hoving, H. J. T., and Lipiński, M. R. 2009. Female reproductive biology, and age of deep-sea squid Histioteuthis miranda from southern Africa. – ICES Journal of Marine Science, 66: 1868–1872. Data on female reproductive strategy and male and female length–weight relationships and age are presented for the mesopelagic squid Histioteuthis miranda. Females exhibit synchronous ovulation, indicating that eggs are spawned at once or over a short period. The maximum potential fecundity seems to range from 89 000 to 148 000 oocytes. Assuming daily deposition of statolith increments, maturing females were 10–15 months old. Male H. miranda mature young (∼6 months) and reach at least 15 months old.

Experiments on sprainting activity of otters ( Lutra lutra ) in the Bieszczady Mountains, southeastern Poland / Observations des épreintes de la loutre ( Lutra lutra ) sur les montagnes du Bieszczady au sud-est de la Pologne

Consecutive surveys of otter spraints of both banks along a 28-km stretch of the River San showed an average of 4.18 deposited spraints/km per day during a 3-week pre-experimental period. The variation in spraint density on particular 1-km-long sections of the river was high and varied from 40 to 145 spraints/km after 3 weeks. Spraint deposition was positively correlated with the proportion of steep and rocky riverbanks, which were characterised by a higher number of potential sprainting sites than those with many flat and undermined banks. Average daily deposition of spraints on the whole 28-km stretch after experimental removal of spraints (experimental period) did not significantly differ compared to the pre-experimental period. However, in sections where otter spraints were removed (n=14), sprainting intensity increased 1.6-fold, while in the control sections (n=14) the defecation ratio decreased 1.5-fold during the first week after removal. Placement of additional spraints of unfamiliar individuals on half the experimental sections did not stimulate otters to increase defecation on these sections compared to those where only old spraints were removed. Otter response to the removal of spraints has a spatial character and is expressed by differentiation in spraint deposition within the home range.

Experiments on sprainting activity of otters ( Lutra lutra ) in the Bieszczady Mountains, southeastern Poland / Observations des épreintes de la loutre ( Lutra lutra ) sur les montagnes du Bieszczady au sud-est de la Pologne

Consecutive surveys of otter spraints of both banks along a 28-km stretch of the River San showed an average of 4.18 deposited spraints/km per day during a 3-week pre-experimental period. The variation in spraint density on particular 1-km-long sections of the river was high and varied from 40 to 145 spraints/km after 3 weeks. Spraint deposition was positively correlated with the proportion of steep and rocky riverbanks, which were characterised by a higher number of potential sprainting sites than those with many flat and undermined banks. Average daily deposition of spraints on the whole 28-km stretch after experimental removal of spraints (experimental period) did not significantly differ compared to the pre-experimental period. However, in sections where otter spraints were removed (n=14), sprainting intensity increased 1.6-fold, while in the control sections (n=14) the defecation ratio decreased 1.5-fold during the first week after removal. Placement of additional spraints of unfamiliar individuals on half the experimental sections did not stimulate otters to increase defecation on these sections compared to those where only old spraints were removed. Otter response to the removal of spraints has a spatial character and is expressed by differentiation in spraint deposition within the home range.

Deposition of protein, fat and energy in lambs of the breed German Merino Landsheep

The purpose of this study was to assess the deposition of fat, protein and energy during the growth period of lambs. Male and female lambs (no. = 54 of each) were fattened (three feeding levels) and slaughtered at various body weights (BW): 18, 30, 45, and 55 kg. Based on the method of the comparative slaughter technique the total body of each animal was analysed. From the data of empty-body gain, fat, protein and energy deposition in the different fattening periods was calculated.The male lambs showed at all body weights tested and in all feeding level groups a lower daily fat deposition and a higher daily protein deposition compared with the female lambs. The deposition of fat increased in both genders with increasing body weight. The amount of increase differed between the three feeding levels. The male lambs showed at all body weights and in all feeding level groups a higher daily gain in body weight but a lower daily deposition of energy compared with the female lambs. However, for the latter, the gender difference rarely reached statistical significance. Parallel to the daily deposition of fat the daily deposition of energy increased in both genders with increasing body weight.Based on the deposition of fat and protein during the growth period of the lambs the body composition was estimated by allometric equations. The equations showed a consistent pattern of protein concentration falling and fat concentration rising with increasing empty body weight. Compared with the literature a higher protein and lower fat concentration in empty body gain was predicted.