scholarly journals Multifrequency discrimination of fish and mysids

2009 ◽  
Vol 66 (6) ◽  
pp. 1106-1110 ◽  
Author(s):  
Thomas Axenrot ◽  
Martin Ogonowski ◽  
Alfred Sandström ◽  
Tomas Didrikas
Keyword(s):  
Early Life ◽  
Sampling Methods ◽  
Dry Weight ◽  
Life Stages ◽  
Early Life Stages ◽  
Ecosystem Monitoring ◽  
Mysis Relicta ◽  
Quantitative Measurements ◽  
Opossum Shrimp ◽  
Backscattering Strength

Abstract Axenrot, T., Ogonowski, M., Sandström, A., and Didrikas, T. 2009. Multifrequency discrimination of fish and mysids. – ICES Journal of Marine Science, 66: 1106–1110. The opossum shrimp (Mysis relicta) is common in many lakes in the northern parts of Eurasia and North America. The shrimp is often an important link in the foodweb for fish, either throughout life or in early life stages. Generally, quantitative measurements of mysids in large volumes of water are difficult to obtain with traditional sampling methods. In this pilot study, measurements of volume-backscattering strength (Sv) at 38, 120, and 200 kHz were used to separate backscattering from fish and mysids. Mysids were sampled with trawls. Where mysids were caught, the correlations between mysid biomass (dry weight) and mean Sv at 120 and 200 kHz were positive (r2 = 0.89 and 0.81, respectively). Where mysids were abundant, the Sv exhibited a characteristic frequency response. This was not found where mysids were scarce or absent. Therefore, areas with great abundances of mysids can be identified, and their biomasses estimated from data collected during ecosystem monitoring.

Preliminary evidence of spawning phenologies of freshwater fish in a wet–dry tropical river: the importance of both wet and dry seasons

2020 ◽  
Vol 71 (2) ◽  
pp. 202 ◽  
Author(s):  
A. J. King ◽  
C. Doidge ◽  
D. Buckle ◽  
K. J. Tyler
Keyword(s):  
Freshwater Fish ◽  
Early Life ◽  
Sampling Methods ◽  
Life Stages ◽  
Young Fish ◽  
Early Life Stages ◽  
Wet Season ◽  
Number Of Species ◽  
Dry Tropics ◽  
Fish Spawning

Wet–dry tropical rivers are characterised by highly predictable, yet highly variable, seasonal flow regimes. The wet season is often regarded as an important period of ecosystem productivity, dispersal and connectivity, and also for freshwater-fish spawning and recruitment. However, few studies have examined fish spawning across hydrological seasons in these rivers. We conducted a pilot study to determine (1) the temporal occurrence (and hence spawning period), and (2) the suitability of standard sampling methods of young fish in the Daly River, Northern Territory, Australia. Fish spawned throughout the year, with spawning phenologies varying substantially among species. The highest diversity and abundance of young fish occurred during the wet season, although early life stages of a high number of species were also present in the dry-season and transition periods. A high number of species spawned all year round, whereas other species had very discrete spawning periods. Three of the four sampling methods tested were successful in catching early life stages and should be employed in future studies. The present study highlighted that all hydrological seasons in the wet–dry tropics are important for fish spawning, and has important implications for future research on the drivers of spawning patterns, and for predicting the effects of flow modifications on freshwater fishes of the wet–dry tropics.

scholarly journals Distribution and lipid composition of early life stages of the cranchiid squid Galiteuthis glacialis (Chun) in the Weddell Sea, Antarctica

1994 ◽  
Vol 6 (2) ◽  
pp. 235-239 ◽  
Author(s):  
Uwe Piatkowski ◽  
Wilhelm Hagen
Keyword(s):  
Total Lipid ◽  
Early Life ◽  
Dry Weight ◽  
Distribution Patterns ◽  
Development Stage ◽  
Weddell Sea ◽  
Life Stages ◽  
Early Life Stages ◽  
Storage Lipids ◽  
Lipid Contents

The relatively small numbers of pelagic cephalopods caught in the RMT-8 samples (0–300 m) in February/March 1983 in the Weddell Sea were dominated by early life stages of the cranchiid squid Galiteuthis glacialis. A total of 48 specimens were caught with dorsal mantle length (ML) ranging from 4–36 mm. They occurred with a mean density of 0.15 ind. × 1000 m−3 and were present in 38% of 33 RMT-8 samples. G. glacialis was the only cranchiid squid found in the Weddell Sea between 66° and 74°S. Its early life stages were concentrated in the layers below the summer thermocline (>50 m) and body sizes appeared to increase towards deeper water layers. For biochemical analyses, nine specimens of G. glacialis (ML 6–18 mm) were sampled in the eastern Weddell Sea between 185–520 m water depth in January/February 1985. Total lipid contents ranged from 8%–11% dry weight (DW) with phospholipids being the main lipid component (43–56% of total lipid). Storage lipids (triacylglycerols) made up 18–26% of total lipid. The relatively low lipid contents may reflect the early development stage of the specimens examined. The data presented give the first information on geographical and vertical distribution patterns of early life stages of G. glacialis in the high-Antarctic Weddell Sea, as well as on their lipid content and composition.

Natural and anthropogenic effects on the early life stages of European anchovy in one of its essential fish habitats, the Guadalquivir estuary

2019 ◽  
Vol 617-618 ◽  
pp. 67-79 ◽  
Author(s):  
GF de Carvalho-Souza ◽  
E González-Ortegón ◽  
F Baldó ◽  
C Vilas ◽  
P Drake ◽  
...  
Keyword(s):  
Early Life ◽  
Anthropogenic Effects ◽  
Life Stages ◽  
Early Life Stages ◽  
European Anchovy ◽  
Guadalquivir Estuary ◽  
Fish Habitats

Incubation Temperature Influences the Duration of Egg Hatching and Early Development in the Boreal Digging Frog, Kaloula Borealis

2020 ◽  
Vol 3 (1) ◽  
pp. ACCEPTED
Author(s):  
Rho-Jeong Rae
Keyword(s):  
Water Temperature ◽  
Early Life ◽  
Rainy Season ◽  
Incubation Temperature ◽  
Life Stages ◽  
Early Life Stages ◽  
Egg Hatching ◽  
Significant Difference ◽  
The Mean ◽  
Hatching Rates

This study investigated the boreal digging frog, Kaloula borealis, to determine the egg hatching period and whether the hatching period is affected by incubation temperature. The results of this study showed that all the eggs hatched within 48 h after spawning, with 28.1% (±10.8, n=52) hatching within 24 h and 99.9% (±0.23, n=49) within 48 h after spawning. A significant difference was noted in the mean hatching proportion of tadpoles at different water temperatures. The mean hatching rates between 15 and 24 h after spawning was higher at a water temperature of 21.1 (±0.2) °C than at 24.1 (±0.2) °C. These results suggest that incubation temperature affected the early life stages of the boreal digging frog, since they spawn in ponds or puddles that form during the rainy season.

First Records and Descriptions of Early Life Stages of Cephalopods from Rapa Nui (Easter Island) and the Nearby Apolo Seamount

2019 ◽  
Vol 73 (1) ◽  
pp. 163 ◽  
Author(s):  
Sergio A. Carrasco ◽  
Erika Meerhoff ◽  
Beatriz Yannicelly ◽  
Christian M. Ibáñez
Keyword(s):  
Early Life ◽  
Easter Island ◽  
Life Stages ◽  
Early Life Stages ◽  
Rapa Nui

Maternal effects influence phenotypes and survival during early life stages in an aquatic turtle

2014 ◽  
Vol 29 (2) ◽  
pp. 268-276 ◽  
Author(s):  
Timothy S. Mitchell ◽  
Jessica A. Maciel ◽  
Fredric J. Janzen
Keyword(s):  
Maternal Effects ◽  
Early Life ◽  
Life Stages ◽  
Early Life Stages
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