scholarly journals Diel patterns in pelagic fish behaviour and distribution observed from a stationary, bottom-mounted, and upward-facing transducer

2004 ◽  
Vol 61 (7) ◽  
pp. 1100-1104 ◽  
Author(s):  
Thomas Axenrot ◽  
Tomas Didrikas ◽  
Charlotte Danielsson ◽  
Sture Hansson
Keyword(s):  
Pelagic Fish ◽  
Strength Distribution ◽  
Fish Distribution ◽  
Target Strength ◽  
Diel Variation ◽  
Fish Behaviour ◽  
Additional Information ◽  
Diel Patterns ◽  
The Baltic ◽  
Survey Planning

Abstract Diel variation in pelagic fish distribution influences hydroacoustic abundance estimates. To study and quantify diel patterns in behaviour and spatial distribution in pelagic fish without causing avoidance reactions or attraction to any floating equipment or vessel we used a bottom-mounted, upward-facing transducer. Light intensities were measured as skylight and underwater light (at 5-m depth). The study was performed in a coastal area in the Baltic Sea, late July to mid-August in 2001 and 2002. The results provided additional information on fish behaviour and distribution valuable for future survey planning and in the analyses of hydroacoustic data from regular surveys in this area. At night, the data on hydroacoustic backscattering (sA) were less variable, the vertical distribution of fish was more even, with fewer fish in the deepest layer, and the percentage of single-echo detections was higher. The tilt angle of fish seemed to differ day and night, but trawling and target-strength distribution results taken together also implied a partial diel change in the fish assemblage in the midwater layers. The processes of formation and disintegration of schools happened rapidly and coincided with day and night transition periods.

Experimental verification of the acoustic characteristics of the clupeoid diel cycle in the Baltic

2005 ◽  
Vol 62 (6) ◽  
pp. 1180-1190 ◽  
Author(s):  
Andrzej Orlowski
Keyword(s):  
Environmental Factors ◽  
Stock Assessment ◽  
Fish Distribution ◽  
Diel Cycle ◽  
Target Strength ◽  
Fish Stock ◽  
Fish Behaviour ◽  
Acoustic Response ◽  
The South ◽  
Gotland Deep

Abstract This paper describes the results of a short-term experiment using measurements of sv from the diel, spatial, clupeoid distribution in the southern Baltic. The aim of the experiment was to verify fish-behaviour characteristics measured over the period from 1995 to 2001. It was also intended to estimate the dynamics of fish behaviour over one separate diel cycle. The studies were based on a 24 h continuous integration of fish echoes using an EY500 echosounder at 38 kHz. Measurements were carried out by RV “Baltica” travelling along the sides of a square of 4 nautical miles at a constant speed of 8 knots. The South Gotland Deep was chosen for the experiment because of the greatest amplitude there of fish vertical, diel migrations within the Polish EEZ. The duration of the experiment was limited by weather conditions, but nearly 300 EDSU samples were collected. 3-D distributions of echoes were correlated to the values of coincident environmental factors of time, depth, water temperature, salinity, and oxygen level. Fish distribution compared with environmental factors is described by different macrosounding visualizations, statistical, and mathematical models. Measurements are compared with the average characteristics of fish behaviour based on data from the autumn acoustic studies between 1995 and 2001 in a wider environment of the Gotland Deep. The results strongly confirmed the instability of the diel acoustic response of fish echoes in both situations. More precise measurements during the experiment indicated the biggest column-scattering strength (Svc) increase during the sunrise period, appearing simultaneously in the whole area. A similar increase was detected by analysis of 1995–2001 data from the South Gotland Deep environment. Major emphasis is given to the explanation of the diel irregularities. Diel instability of fish acoustic response can significantly effect the results of target-strength measurements (up to 400% during the sunrise) and, as a consequence, the calibration of acoustic fish stock-assessment models.

ESTIMATION OF PELAGIC FISH DISTRIBUTION IN INNER BAY WITH MACHINE LEARNING

2019 ◽  
Vol 75 (2) ◽  
pp. I_1129-I_1134
Author(s):  
Takaharu HAMADA ◽  
Tsukasa YOSHIDA ◽  
Hiroshi OKAMURA ◽  
Takeshi HARA ◽  
Teruaki SUZUKI
Keyword(s):  
Machine Learning ◽  
Pelagic Fish ◽  
Fish Distribution

Physical and biological drivers of pelagic fish distribution at high spatial resolution in two Patagonian Gulfs

2021 ◽  
Author(s):  
Elvio Agustín Luzenti ◽  
Guillermo Martín Svendsen ◽  
Mariana Degrati ◽  
Nadia Soledad Curcio ◽  
Raúl Alberto González ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Pelagic Fish ◽  
Fish Distribution

Hudson River Fishes and their Environment

2006 ◽  
Keyword(s):  
Power Plant ◽  
Power Plants ◽  
Near Field ◽  
Hudson River ◽  
Pelagic Fish ◽  
Fish Abundance ◽  
Fish Distribution ◽  
Fish Density ◽  
Negative Effects ◽  
Abundance And Distribution

<em>Abstract.</em>—Pelagic fish abundance and distribution was estimated acoustically at Bowline and Indian Point power plants on the Hudson River, New York, during July, August, and September 1996, in a study designed to determine size-specific spatial and temporal fish abundance and distribution with respect to environmental variables (i.e., photoperiod, depth strata, field). August yielded the greatest (<EM>P </EM>< 0.05) mean density of fish at both power plants. Fish were concentrated in Bowline’s near-field (lagoon) region, thus increasing the potential for deleterious impingement and entrainment effects there. For all size classes, mean fish density was greatest during darkness at both power plants. Generally, the two power plants exhibited similar trends in mean fish abundance with respect to water depth and photoperiod. During July and August mean fish density was significantly higher between 1.5 and 4.5 m (depth strata one) of depth at both power plants. Bowline’s mean fish density was greater under near-field, shallow depth (depth strata one) darkness during July and August. Bowline’s isolated and bathymetrically complex near-field lagoon concentrated pelagic fish compared to the river proper. Hydroacoustics were useful in providing a detailed map of fish distribution relative to each power plant over the course of a few days each month. Hydroacoustic monitoring could mitigate negative effects to pelagic fish at existing and proposed power plants, through sighting of power plant water intake structures or by providing a biological basis for modified production cycles.

Diel pattern of plasma T3 and T4 levels in Baltic salmon parr (Salmo salar L.) during two seasons

1984 ◽  
Vol 62 (4) ◽  
pp. 643-646 ◽  
Author(s):  
Magnus Rydevik ◽  
Kenneth Lindahl ◽  
Gunnar Fridberg
Keyword(s):  
Water Temperature ◽  
Salmo Salar ◽  
Regulatory Mechanism ◽  
Diel Variation ◽  
Diel Pattern ◽  
Fish Feeding ◽  
Diel Patterns ◽  
Salmon Parr ◽  
Peak Value

In March (sunrise at 0530, sunset at 1800, water temperature 0.04 °C, and the fish not feeding) plasma T3 showed no diel variation and plasma T4 varied only slightly. In May (sunrise at 0200, sunset at 2120, water temperature 9.0 °C, and the fish feeding) plasma T4 showed a pronounced diel variation with its peak value appearing just before sunset and its nadir occurring at 0800. The plasma T3 level varied slightly with its peak value at 0400. The constant or slightly varying diel levels of plasma T3 suggests an efficient regulatory mechanism that maintains the plasma T3 concentration relatively stable throughout the 24 h. It is concluded that the diel patterns of T4 and T3 are dependent on factors related to the season. The influence of photoperiod and feeding on the diel pattern of T4 is discussed.

Survey gear calibration independent of spatial fish distribution

2004 ◽  
Vol 61 (4) ◽  
pp. 636-647 ◽  
Author(s):  
Peter Lewy ◽  
J Rasmus Nielsen ◽  
Holger Hovgård
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Survey Design ◽  
Fish Distribution ◽  
Simulation Studies ◽  
Conversion Factors ◽  
The Baltic ◽  
Standard Software ◽  
Track Line ◽  
Stock Abundance

Trawl surveys provide important information for evaluation of relative stock abundance fluctuations over time. Therefore, when survey gears or vessels are changed, it is important to compare the efficiency and selectivity of old and new gears and vessels. A method for estimation of conversion factors is developed based on a survey design where paired hauls are taken in the same trawl track line. The method explicitly accounts for changes in fish density caused by trawling disturbance. A generalized linear model for paired hauls catches is analytically derived and the gear conversion and disturbance parameters with their precision are obtained using standard software. Simulation studies carried out additionally showed that the estimated conversion factors were practically unbiased. Because of the independence of the spatial fish distribution, the new method is preferable to the traditional paired hauls design for which it is generally not possible to obtain the statistical properties of the estimated conversion factors. The paper is concluded with suggestions on how to optimize survey design. The method was used to estimate conversion factors for Atlantic cod (Gadus morhua) from Danish gear calibration experiments in the Baltic Sea.

scholarly journals Measuring herring densities with one real and several phantom research vessels

2009 ◽  
Vol 66 (6) ◽  
pp. 1264-1269 ◽  
Author(s):  
Ruben Patel ◽  
Egil Ona
Keyword(s):  
Pelagic Fish ◽  
Target Strength ◽  
Fish Biomass ◽  
Marine Science ◽  
Lateral Aspect ◽  
Multibeam Sonar ◽  
The Real ◽  
Backscattering Strength ◽  
The Mean

Abstract Patel, R., and Ona, E. 2009. Measuring herring densities with one real and several phantom research vessels. – ICES Journal of Marine Science 66: 1264–1269. Vessel-induced avoidance can potentially cause a large bias in acoustic estimates of schooling, pelagic-fish biomass. This paper presents a method for quantifying this uncertainty. Volume-backscattering strength (Sv) from a horizontally projecting, multibeam sonar (Simrad MS70) is resampled to form synthetic, vertical, echosounder beams to the side of the survey vessel. These data are analysed as if they were collected from phantom vessels surveying parallel transects at fixed ranges from the real vessel. The nautical-area-backscattering coefficients (sA) from the synthetic echograms are compared with those measured by conventional 70 and 120 kHz echosounders (Simrad EK60) on the real vessel. Data collected in 2006 from schools of Norwegian spring-spawning herring are used to illustrate the method and explore its limitations. Potential effects of vessel-induced avoidance are evaluated by comparing the mean sA values observed from the phantom vessels with those observed from the real vessel. The technique also allows direct estimates of the mean lateral-aspect target strength of in situ herring.

scholarly journals DISTRIBUSI KEPADATAN IKAN PELAGIS DI PERAIRAN PANTAI UTARA JAWA BAGIAN TIMUR, PULAU-PULAU SUNDA, DAN LAUT FLORES

2017 ◽  
Vol 13 (3) ◽  
pp. 223
Author(s):  
Asep Priatna ◽  
Mohammad Natsir
Keyword(s):  
Environmental Factor ◽  
Pelagic Fish ◽  
Target Strength ◽  
Fish Density ◽  
Small Pelagic Fish ◽  
Pelagic Fishes ◽  
East Region ◽  
Marginal Areas ◽  
Near Shore ◽  
Distribution Of Fish

Penelitian ini bertujuan untuk mempelajari distribusi spasial kepadatan ikan pelagis serta hubungan dengan kondisi perairan pada musim peralihan di perairan pantai utara Jawa bagian timur dan Laut Flores, berdasarkan pada pengambilan contoh akustik dan 34 stasiun oseanografi pada bulan Oktober 2005. Data target strength menunjukkan bahwa rata-rata ukuran ikan pelagis yang terdeteksi di perairan pantai utara Jawa bagian timur adalah 10 sampai dengan 56 cm. Ukuran ikan di daerah lepas pantai lebih kecil dibanding daerah dekat pantai. Pada musim peralihan, kondisi suhu dan salinitas perairan relatif homogen. Sehingga faktor tersebut kurang signifikan terhadap distribusi keberadaan ikan. Diduga faktor lingkungan lain seperti faktor biologi dan kimia, berperan dalam pola penyebaran ikan pelagis kecil di perairan ini. Di Laut Flores dan sekitar Pulau-Pulau Sunda, densitas ikan tertinggi pada stratum 10 sampai dengan 50 m dengan ukuran 10 sampai dengan 20 cm terutama di beberapa lahan marginal seperti sekitar selat dan kepulauan. Selain merupakan lapisan tercampur di mana kondisi suhu dan salinitas relatif stabil pada kedalaman 10 sampai dengan 50 m, lahan marginal merupakan daerah subur tempat pertemuan 2 massa air yang berbeda yang membentuk front diharapkan merupakan tempat berkumpul ikan. Lapisan termoklin yang bersifat lemah berada di bawah 50 m, hal ini mempengaruhi densitas ikan yang semakin rendah pada kedalaman lebih dari 50 m. Ikan pelagis yang berada pada lapisan termoklin mempunyai ukuran yang lebih besar yaitu 14 sampai dengan 40 cm. Pada musim yang sama, rata-rata kepadatan dan ukuran ikan pelagis kecil di wilayah timur lebih rendah daripada sebelah barat. The aim of this research is to study the distribution of spasial density of pelagic fish with waters condition at intermonsoon in north of Java coast waters part of east and Flores Sea, based on acoustic sampling and 34 oceanography stations in October 2005. The target strength of fish indicated that pelagic fish measure in north of Java coast waters part of east is about 10 to 56 cm. Fish sizes in offshore is smaller than near shore. At intermonsoon, the waters condition of temperature and salinity was homogeneous relatively. Therefore, that are less to distribution of fish density. Anticipated, the others environmental factor like chemical and biological, was influenced to distribution of small pelagic fish in this area. In Flores Sea and Sunda Islands, the highest of fish density at 10 to 50 m and fish sizes about 10 to 20 cm especially in some marginal areas near archipelago and strait. At 10 to 50 m is mixed layer, where temperature and salinity was relative stabilize, the maginal areas is fertility waters which is passage of the shifting by two different water masses and front were formed . The weak termocline was formed below 50 m, maked fish density are progressively lower below 50 m. The pelagic fish residing in termocline layers have larger ones measure than stratum 10 to 50 m is about 14 to 40 cm. On same season, the fish measure and density of small pelagic fishes in east region is lower than at westside.

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