scholarly journals Use of data storage tags to quantify vertical movements of cod: effects on acoustic measures

2004 ◽  
Vol 61 (7) ◽  
pp. 1062-1070 ◽  
Author(s):  
O. Heffernan ◽  
D. Righton ◽  
K. Michalsen
Keyword(s):  
Data Storage ◽  
Gadus Morhua ◽  
Vertical Movement ◽  
Neutral Buoyancy ◽  
Vertical Movements ◽  
Acoustic Measures ◽  
Depth Data ◽  
Basic Assumptions ◽  
Use Of Data ◽  
Sampling Intervals

Abstract Depth data from archival tagging studies of cod (Gadus morhua) were used in three different analyses with the aim of testing basic assumptions of cod behaviour. Examination of post-release depth profiles from cod tagged in the Barents, North, and Irish Seas revealed that some cod underwent a post-release period of adaptation to increasing depth as they readjusted their buoyancy to its pre-tagging level. This depth adaptation behaviour was characterized by gradually increasing mean depth, and enabled the calculation of neutral-buoyancy compliant descent rates, which were less than 1 m h−1. Estimated rates of vertical movement were shown to be highly dependent upon the frequency at which depth was sampled. Maximum estimated rates of ascent and descent from sampling intervals of 10 or 15 min were inconsistent with the maintenance of neutral buoyancy, but estimates from sampling intervals greater than 1 h were not. Calculation of tilt angles using depth data sampled at 10-s intervals showed that cod were often tilted more than 5° relative to the horizontal, and that this effect was more pronounced at night. These findings suggest that basic assumptions regarding cod physiology and behaviour require revision if the accuracy and precision of acoustic methods are to be improved.

scholarly journals Vertical migrations of saithe (Pollachius virens) in Icelandic waters as observed with data storage tags

2012 ◽  
Vol 69 (8) ◽  
pp. 1372-1381 ◽  
Author(s):  
Hlynur Armannsson ◽  
Sigurður Þór Jónsson
Keyword(s):  
Data Storage ◽  
Vertical Movement ◽  
Target Strength ◽  
Night Time ◽  
Neutral Buoyancy ◽  
Seasonal Differences ◽  
Vertical Movements ◽  
Vertical Range ◽  
Data Storage Tags ◽  
Icelandic Waters

Abstract Armannsson, H., and Jónsson, S. Þ. 2012. Vertical migrations of saithe (Pollachius virens) in Icelandic waters as observed with data storage tags. – ICES Journal of Marine Science, 69: . Knowledge of fish behaviour is important for general understanding of fish life history and responses to environmental and biological conditions. Vertical migrations can affect bottom trawl indices of the fish through their availability to the trawl and acoustic indices through changes in target strength. Here we present results based on data sets of hourly recordings of depth from 51 saithe. The data were analysed with respect to diel and seasonal differences in saithe vertical movement. Duration and extent of vertical movements were analysed with 1 min resolution, and the daily vertical range (DVR) was analysed with respect to potential use of the free vertical range (FVR). Our results show diel and seasonal differences in hourly depth changes of saithe, indicating reduced activity during night-time and in winter. Individual saithe are capable of rapid depth changes in <1 min, often of the same order as the maximum observed in movements of longer duration. The DVR often exceeded the FVR, and in some instances exceeded critical limits, indicating that saithe may at times only maintain neutral buoyancy near the upper limit of their daily vertical range.

scholarly journals Monitoring coastal northern cod: towards an optimal survey of Smith Sound, Newfoundland

2003 ◽  
Vol 60 (3) ◽  
pp. 453-462 ◽  
Author(s):  
George A Rose
Keyword(s):  
Gadus Morhua ◽  
Sampling Error ◽  
Vertical Movement ◽  
Target Strength ◽  
Biomass Estimation ◽  
Night Time ◽  
Acoustic Measures ◽  
Rate Of Increase ◽  
Northern Cod ◽  
Age Structured

Abstract The extant, coastal northern cod (Gadus morhua) have over-wintered and spawned in Smith Sound, Newfoundland, since 1995, and acoustic surveys have been conducted in several seasons since then. Cod move into the Sound in late fall, over-winter in a dense, size- and age-structured aggregation, spawn between late March and early June and then disperse into and beyond Trinity Bay during summer to feed. The optimal survey time for biomass estimation is January–February, when the waters are ice-free and the cod are in mono-specific, relatively stationary, and well-defined aggregations with the highest densities and are typically clear of “bottom returns”. Biomass surveys have been conducted in mid-January since 1999. An error analysis indicated the main sources of uncertainty to be density variability and target strength (TS). Repeated quasi-synoptic (10 h) surveys were the optimal means of producing an estimate of uncertainty about population size. Some vertical movement led to night-time surveys consistently having higher estimates than day-time surveys by approximately 15%. Detectability ranged from 73 to 86% and deadzone-corrected, acoustic measures did not differ from swept-area densities found by bottom trawling. Biomass scaling by TS used length-dependant dB/kg to reduce the size-sampling error. Overall, population biomass doubled in approximately 7 years, consistent with a rate of increase around 0.2, largely through recruitment. The surveys are internally consistent and indicate instantaneous rates of mortality among year classes of 0.3 to >2 (very high on older fish) and provide a method for monitoring the annual biomass (cv<40%).

scholarly journals Otolith shape differences between ecotypes of Icelandic cod (Gadus morhua) with known migratory behaviour inferred from data storage tags

2017 ◽  
Vol 74 (12) ◽  
pp. 2122-2130 ◽  
Author(s):  
Hlynur Bardarson ◽  
Bruce. J. McAdam ◽  
Vilhjalmur Thorsteinsson ◽  
Einar Hjorleifsson ◽  
Gudrun Marteinsdottir
Keyword(s):  
Data Storage ◽  
Gadus Morhua ◽  
Fourier Transforms ◽  
Function Analysis ◽  
Variable Temperature ◽  
Otolith Shape ◽  
Use Of Data ◽  
Data Storage Tags ◽  
Migratory Strategies ◽  
Definition Of

Otolith shape can be used to identify ecotypes of the Icelandic cod (Gadus morhua) stock. The use of data storage tags has increased our knowledge of the stock structure of Icelandic cod. The profiles of tagged cod reveal different migratory strategies. This has led to the definition of two ecotypes within the cod stock. Frontal ecotypes reside in deep waters during feeding season and express a highly variable temperature profile associated with thermal fronts, while coastal ecotypes stay in shallow waters all year round. In this study, the data storage tag profiles were analysed with cluster analysis, which revealed the existence of an intermediate behaviour that expresses a variable depth profile and feeding migration that is both shorter in time and not as deep. The main objective was to develop a morphological key based on otoliths to distinguish the ecotypes. The shape of the otoliths was extracted with shape measurements and fast Fourier transforms. A discriminant function analysis indicated a difference in morphology between the ecotypes, resulting in successful classification.

The Swimbladder and the Vertical Movement of Teleostean Fishes

1951 ◽  
Vol 28 (4) ◽  
pp. 553-566
Author(s):  
F. R. HARDEN JONES
Keyword(s):  
Body Wall ◽  
Bladder Wall ◽  
Relative Size ◽  
Perca Fluviatilis ◽  
Vertical Movement ◽  
Physical Factors ◽  
Vertical Movements ◽  
Perch Perca Fluviatilis ◽  
Percentage Volume ◽  
Two Factors

The vertical movements of a teleostean fish may be restricted by the presence of the swimbladder, which will increase or decrease in volume when the fish moves up or down in the water. It is shown that the restriction that the swimbladder imposes to vertical movements involving a reduction in pressure will depend on physical factors such as (1) The resistance that the bladder and body wall offer to the expansion of the bladder gas. (2) The percentage volume of the swimbladder and the density change of the fish when it is subjected to a reduction in pressure. (3) The pressure reduction that leads to the rupture of the bladder wall. A distinction is made between rapid and slow movements. In the former the compensatory ability of the fish must be considered and in the latter the speed with which the fish can accommodate itself to pressure changes. An equation is derived from which the minimum speed at which a physoclist can migrate from deep to shallow water can be calculated. To solve the equation two factors must be determined experimentally. Various experiments are described which were made on the perch, Perca fluviatilis, the wrasse, Crenilabrus melops, the rockling, Onos mustela and the dragonet, Callionymus lyra. The results showed that there was a relation between the relative size of the swimbladder and the change in the density of a fish when it is subjected to a reduction in pressure; that the bladder and body wall of the perch offer little resistance to the expansion of the bladder gas; and that the danger of the bladder wall rupturing might restrict the extent of rapid movements made by the perch. Experiments on the restriction that the swimbladder imposes to the rapid and slow vertical movements of the perch will be described in a following paper.

scholarly journals Horizontal-vertical movement relationships: Adélie penguins forage continuously throughout provisioning trips

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Javed Riaz ◽  
Sophie Bestley ◽  
Simon Wotherspoon ◽  
Louise Emmerson
Keyword(s):  
Environmental Conditions ◽  
Optimal Foraging ◽  
Three Dimensional ◽  
Spatial Location ◽  
Vertical Movement ◽  
Foraging Activity ◽  
Directed Movement ◽  
Vertical Movements ◽  
Movement Trajectories ◽  
Adélie Penguins

Abstract Background Diving marine predators forage in a three-dimensional environment, adjusting their horizontal and vertical movement behaviour in response to environmental conditions and the spatial distribution of prey. Expectations regarding horizontal-vertical movements are derived from optimal foraging theories, however, inconsistent empirical findings across a range of taxa suggests these behavioural assumptions are not universally applicable. Methods Here, we examined how changes in horizontal movement trajectories corresponded with diving behaviour and marine environmental conditions for a ubiquitous Southern Ocean predator, the Adélie penguin. Integrating extensive telemetry-based movement and environmental datasets for chick-rearing Adélie penguins at Béchervaise Island, we tested the relationships between horizontal move persistence (continuous scale indicating low [‘resident’] to high [‘directed’] movement autocorrelation), vertical dive effort and environmental variables. Results Penguins dived continuously over the course of their foraging trips and lower horizontal move persistence corresponded with less intense foraging activity, likely indicative of resting behaviour. This challenges the traditional interpretation of horizontal-vertical movement relationships based on optimal foraging models, which assumes increased residency within an area translates to increased foraging activity. Movement was also influenced by different environmental conditions during the two stages of chick-rearing: guard and crèche. These differences highlight the strong seasonality of foraging habitat for chick-rearing Adélie penguins at Béchervaise Island. Conclusions Our findings advance our understanding of the foraging behaviour for this marine predator and demonstrates the importance of integrating spatial location and behavioural data before inferring habitat use.

Thermoregulatory behaviour in cod: Is the thermal preference in free-ranging adult Atlantic cod affected by food abundance?

2019 ◽  
Vol 76 (9) ◽  
pp. 1515-1527 ◽  
Author(s):  
Björn Björnsson
Keyword(s):  
Growth Rate ◽  
Data Storage ◽  
Gadus Morhua ◽  
Cold Water ◽  
Atlantic Cod ◽  
Vertical Mixing ◽  
Metabolic Energy ◽  
Fat Reserves ◽  
Free Ranging ◽  
Thermoregulatory Behaviour

This study supports the hypothesis that well-fed cod (Gadus morhua) seek higher temperatures to increase growth rate, and poorly fed cod select lower temperatures to save metabolic energy. Depth and temperature of free-ranging adult cod (44–79 cm) were studied with data storage tags as part of a ranching project in an Icelandic fjord. Forage fish were regularly provided at four feeding stations where cod formed distinct “herds” (herd cod) that did not mingle much with the rest of the unconditioned cod in the fjord (wild cod). Several parameters (stomach fullness, liver index (fat reserves), condition factor, and growth rate) indicated that food intake was much greater in herd cod than in wild cod. In August, when the thermocline was well established, the herd cod remained in shallow (15–35 m) and warm water (8–10 °C), whereas the wild cod stayed in deep (80–90 m) and cold water (3–4 °C), but occasionally both groups explored depths and temperatures outside their preferred range. After vertical mixing in autumn when thermoregulation was not possible, the depth difference between the two groups decreased significantly.

scholarly journals Vertical migration in adult Atlantic cod (Gadus morhua)

2007 ◽  
Vol 64 (12) ◽  
pp. 1747-1760 ◽  
Author(s):  
Espen Strand ◽  
Geir Huse
Keyword(s):  
Vertical Migration ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Pelagic Zone ◽  
Neutral Buoyancy ◽  
Visual Predation ◽  
Trade Offs ◽  
Key Factor ◽  
Pelagic Prey ◽  
Benthic Prey

We investigate the trade-offs associated with vertical migration and swimming speed of Atlantic cod (Gadus morhua) using an adaptive individual-based model. Simulations with varying distribution and occurrence of prey, with and without swimbladder constraints, and visual predation were performed. Most simulations resulted in cod migrations between the bottom and pelagic zones. In simulations with high probability of encountering pelagic prey, the cod spent the daytime in the pelagic zone, moving to the bottom to feed only when no pelagic prey were encountered. At night the cod stayed in the pelagic zone to attain neutral buoyancy. In simulations with low occurrence of pelagic prey or high visual predation pressure, the cod remained at the bottom feeding on the consistently present benthic prey. If the pelagic prey occurred far above the sea floor or there were no benthic prey, the cod abandoned all bottom contact. The study thus predicts that the probability of encountering energy-rich pelagic prey is the key factor in driving vertical migration in adult cod. Buoyancy regulation is further shown to be an important constraint on vertical migration.

Research of Data Server Application Software for NBI Mechanical Control on EAST

2012 ◽  
Vol 214 ◽  
pp. 538-542 ◽  
Author(s):  
Xiao Dan Zhang ◽  
Zhi Min Liu ◽  
Peng Sheng ◽  
Chun Dong Hu ◽  
Yuan Zhe Zhao
Keyword(s):  
Data Storage ◽  
C Language ◽  
Use Of Data ◽  
Remote Server ◽  
Data Value ◽  
Server Software ◽  
And Control ◽  
Measurement And Control ◽  
Server Application ◽  
Control Layer

For the sake of achieving to manage and query the experimental data scientifically, as well as relevant experiment information for Neutral Beam Injection (NBI) system, NBI Data Server software is developed for data exchanging between the remote server control layer and the field measurement and control layer, data storage and querying. Experimental results show that managing data scientifically can ensure data security and making best use of data will bring data value into full play. NBI Data Server software is programmed by C language, developed with Client/Server program model and multi-threading technology, runs on linux operating system. Experiments show that NBI data server software can work steadily and reliably.

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