The relations between 0+ fish density, zooplankton size and the vulnerability of pikeperch, Stizostedion lucioperca, to angling in the Frisian lakes

Hydrobiologia ◽  
1982 ◽  
Vol 95 (1) ◽  
pp. 321-336 ◽  
Author(s):  
W. L. T. van Densen ◽  
J. Vijverberg
Keyword(s):  
Fish Density ◽  
Zooplankton Size ◽  
Stizostedion Lucioperca

SHALLOW WATER HABITAT MAPPING AND REEF FISH STOCK ESTIMATION USING HIGH RESOLUTION SATELLITE DATA

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Vincentius P. Siregar ◽  
Sam Wouthuyzen ◽  
Andriani Sunuddin ◽  
Ari Anggoro ◽  
Ade Ayu Mustika
Keyword(s):  
High Resolution ◽  
Reef Fish ◽  
Satellite Imagery ◽  
Field Survey ◽  
Coral Cover ◽  
Fish Density ◽  
Fish Stock ◽  
Benthic Habitat ◽  
Live Coral ◽  
Stock Estimation

Shallow marine waters comprise diverse benthic types forming habitats for reef fish community, which important for the livelihood of coastal and small island inhabitants. Satellite imagery provide synoptic map of benthic habitat and further utilized to estimate reef fish stock. The objective of this research was to estimate reef fish stock in complex coral reef of Pulau Pari, by utilizing high resolution satellite imagery of the WorldView-2 in combination with field data such as visual census of reef fish. Field survey was conducted between May-August 2013 with 160 sampling points representing four sites (north, south, west, and east). The image was analy-zed and grouped into five classes of benthic habitats i.e., live coral (LC), dead coral (DC), sand (Sa), seagrass (Sg), and mix (Mx) (combination seagrass+coral and seagrass+sand). The overall accuracy of benthic habitat map was 78%. Field survey revealed that the highest live coral cover (58%) was found at the north site with fish density 3.69 and 1.50 ind/m2at 3 and 10 m depth, respectively. Meanwhile, the lowest live coral cover (18%) was found at the south site with fish density 2.79 and 2.18  ind/m2 at 3 and 10 m depth, respectively. Interpolation on fish density data in each habitat class resulted in standing stock reef fish estimation:  LC (5,340,698 ind), DC (56,254,356 ind), Sa (13,370,154 ind), Sg (1,776,195 ind) and Mx (14,557,680 ind). Keywords: mapping, satellite imagery, benthic habitat, reef fish, stock estimation

ERADICATION OF INVASIVE TAMARIX RAMOSISSIMA ALONG A DESERT STREAM INCREASES NATIVE FISH DENSITY

2005 ◽  
Vol 15 (6) ◽  
pp. 2072-2083 ◽  
Author(s):  
Theodore A. Kennedy ◽  
Jacques C. Finlay ◽  
Sarah E. Hobbie
Keyword(s):  
Tamarix Ramosissima ◽  
Fish Density ◽  
Native Fish ◽  
Desert Stream

scholarly journals FACTORS INFLUENCING THE PERFORMANCE OF TRAWL OPERATION IN THE WATERS AREA OF TARAKAN

2018 ◽  
Vol 23 (2) ◽  
pp. 79
Author(s):  
Asep Priatna ◽  
Suprapto Suprapto
Keyword(s):  
Principal Component ◽  
Bottom Trawl ◽  
Fish Density ◽  
Trawl Survey ◽  
Door Opening ◽  
Test Of Significance ◽  
Towing Speed ◽  
Bottom Depth ◽  
Catch Composition

Any fish on swept area of bottom trawl could not be caught due to some technical factors during towing. However, it could be estimated by integrated of bottom trawl and acoustic survey. This paper describes the determination of some factors that affect the performance of trawl net during the bottom trawl survey in the waters of Tarakan. Surveys were carried out in May, August, and November 2012. A total of 57 stations of simultaneously acoustic-trawl were completed. Data collected from each station include catch composition, and variables of trawling operation (i.e. bottom depth, warp length, trawl door opening, towing speed, towing duration, and acoustic fish density). Principal component analysis was applied to identify variables might impact of trawling performance (i.e. fish density at the waters area, towing speed, towing duration, warp length, horizontal opening of trawl door, density of non-demersal at cod end, and bottom depth). Both towing speed and towing duration were not major component for trawl operation. According to test of significance for four variables (i.e. bottom depth, warp length, horizontal opening, biota non-demersal at cod end) which affected to fish density at waters area, that both of variable (i.e. warp length and bottom depth) were significant as the principal components for the performance of bottom trawl. 

scholarly journals POLA SEBARAN IKAN PADA MUSIM BARAT DAN PERALIHAN DI PERAIRAN UTARA JAWA TENGAH

2017 ◽  
Vol 14 (1) ◽  
pp. 67
Author(s):  
Asep Priatna ◽  
Mohammad Natsir
Keyword(s):  
Food Source ◽  
Target Strength ◽  
Fish Density ◽  
Current Direction ◽  
North West ◽  
Pelagic Fishes ◽  
Central Java ◽  
The Difference ◽  
West Monsoon ◽  
Demersal Fishes

Penelitian ini bertujuan untuk mempelajari perbedaan pola sebaran ikan pada musim barat dan peralihan di perairan utara Semarang sampai dengan Brebes, berdasarkan pada pengambilan contoh akustik dan oseanografi pada bulan Desember 2005 dan Mei 2006. Hasil menunjukkan secara spasial, pada musim barat di perairan utara Semarang sampai dengan Brebes kepadatan ikan pelagis lebih besar di daerah yang lebih dangkal yaitu sebelah selatan pada kedalaman <40 m, semakin ke tengah kepadatan semakin berkurang. Dilihat dari nilai target strength yang terdeteksi yaitu antara -60 sampai dengan -50 dB bahkan didominasi oleh ikan -60 sampai dengan -55 dB, sasaran merupakan ikan pelagis kecil yang rata-rata mempunyai ukuran 4 sampai dengan 12,5 cm. Pada musim peralihan sebaran kepadatan ikan pelagis kecil cenderung lebih merata dengan jumlah yang lebih rendah daripada jumlah ikan pada musim barat. Faktor pergerakan arah arus dan keberadaan sumber makanan yang lebih besar pada musim barat diduga merupakan penyebab perbedaan tersebut. Ikan pelagis kecil pada musim peralihan berukuran lebih besar dibandingkan ketika musim barat, dengan nilai target strength yang terdeteksi antara -60 sampai dengan -45 dB atau sekitar 4 sampai dengan 22 cm dan didominasi oleh ikan yang berukuran -55 sampai dengan -50 dB atau sekitar 7 sampai dengan 12,5 cm. Sebaran kepadatan Ikan demersal hampir merata pada ke-2 musim tersebut, pada musim peralihan kepadatan lebih rendah daripada musim barat. Ikan demersal pada musim barat terdiri atas ikan berukuran kecil (-55 sampai dengan -50 dB) atau sekitar 7 sampai dengan 12,5 cm terutama di daerah pada kedalaman <40 m, semakin ke tengah ukuran semakin besar yaitu antara -50 sampai dengan -45 dB atau sekitar 12,5 sampai dengan 22 cm. Pada musim peralihan, ikan demersal dengan target strength -55 sampai dengan -50 dB terdapat di kedalaman <40 m. Ikan demersal dengan ukuran -50 sampai dengan -45 dB mendominasi periode ini. Pada kedalaman >45 m terdeteksi ikan -45 sampai dengan -35 dB yang berkisar 22 sampai dengan 70 cm. The aim of this study is to understood the difference of fish pattern distributions at North West and intermonsoon in North of Central Java waters, based on acoustic and oceanography sampling in December 2005 and May 2006. At North West monsoon, the density of pelagic fishes was more gathering in narrower areas <40 m, and low fish density was going to middle areas. Seen from target strength the value was detected about -60 to -50 dB and it was dominated by fishes -60 to -55 dB, the targets for small pelagic fishes are about 4 to 12,5 cm. At the intermonsoon, distribution of small pelagic fishes density tends to be flat, but fish density at this time was the lower than North West monsoon. The higly current direction and food source factor at North West monsoon may cause this difference. The size of small pelagic fishes at the intermonsoon was bigger than fishes at North West monsoon, which target strength value was detected about -60 to -45 dB or 4 to 22 cm and dominated by fishes -55 to -50 dB of about 7 to 12,5 cm. The density distribution of demersal fishes almost flat at both monsoon. How ever at intermonsoon, the demersal fishes density was lower than that at North and West season. Demersal fishes at North West monsoon consisted of small fishes (-55 to -50 dB) with size of about 7 to 12,5 cm especially in narrow areas <40 m, and fish sizes the larger (-50 to -45 dB or 12,5 to 22 cm) were going to the middle areas. At intermonsoon, there were demersal fishes with target strength -55 to -50 dB at <40 m. Demersal fishes with target strength -55 to -50 dB were dominant at this time. At areas >45 m it was detected fishes of -45 to -35 dB target strength of about 22 to 70 cm.

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