A new improved method to compute swept area estimates of biomass from commercial catch rate data: application to Namibian orange roughy (Hoplostethus atlanticus)

2002 ◽  
Vol 56 (1) ◽  
pp. 69-88 ◽  
Author(s):  
Carola Kirchner ◽  
Murdoch McAllister
Keyword(s):  
Catch Rate ◽  
Rate Data ◽  
Improved Method ◽  
Orange Roughy ◽  
Commercial Catch ◽  
Data Application ◽  
Swept Area ◽  
Hoplostethus Atlanticus

scholarly journals Did over-reliance on commercial catch rate data precipitate the collapse of northern cod?

2005 ◽  
Vol 62 (6) ◽  
pp. 1139-1149 ◽  
Author(s):  
Peter A. Shelton
Keyword(s):  
Population Size ◽  
Functional Relationship ◽  
Catch Rate ◽  
Research Vessel ◽  
Rate Data ◽  
Commercial Catch ◽  
Stock Size ◽  
Functional Relationships ◽  
Northern Cod ◽  
Catch Rates

Abstract It has been suggested that a number of “lessons” can be learned from the collapse of the northern cod stock off Newfoundland and Labrador. However, not all purported lessons have been validated with available data. One lesson is thought to be that over-reliance on commercial catch rate data and an incorrect assumption regarding the functional relationship between catch rate and population size were major contributors to overestimating stock size, precipitating the collapse. The current study describes calibration approaches used in assessments, and evaluates alternative functional relationships between commercial catch rates and stock size. In addition, historical population size is re-estimated using only research vessel data and compared with estimates obtained based on both commercial catch rate and research vessel data. Calibration with commercial catch rate contributed to overestimating stock size in some years, but there is no evidence that the assumed functional relationship between commercial catch rate and population size was a significant factor in the collapse.

Use of acoustics to assess a small aggregation of orange roughy, Hoplostethus atlanticus (Collett), off the eastern coast of Tasmania

1993 ◽  
Vol 44 (3) ◽  
pp. 473 ◽  
Author(s):  
NG Elliott ◽  
RJ Kloser
Keyword(s):  
Target Strength ◽  
Eastern Coast ◽  
Orange Roughy ◽  
Commercial Catch ◽  
Acoustic Data ◽  
The Mean ◽  
Small Aggregation ◽  
Hoplostethus Atlanticus ◽  
Echo Sounder

A relatively small aggregation of orange roughy (Hoplostethus atlancticus) was located in April 1989 off the eastern coast of Tasmania. A Simrad EK400 (38 kHz) scientific echo-sounder was used to survey the aggregation over a period of eight days, during which time the aggregation was commercially fished. The aggregation was confined to an area of approximately 4 km2, with the dimensions of the aggregation varying within and between days. High densities of orange roughy were located near the bottom on some days and more than 24 m off the bottom on others. Average fish densities during the survey and an estimate of the extremes of densities (fish m-3) are presented. Estimates of the original biomass of this aggregation as obtained from acoustic data and commercial catch-and-effort data are compared, and the mean target strength of the population is estimated.

Age determination and growth of orange roughy (Hoplostethus atlanticus): a comparison of annulus counts with radiometric ageing

1995 ◽  
Vol 52 (2) ◽  
pp. 391-401 ◽  
Author(s):  
David C. Smith ◽  
Simon G. Robertson ◽  
Gwen E. Fenton ◽  
Stephen A. Short
Keyword(s):  
Age Determination ◽  
Percentage Reduction ◽  
Age At Maturity ◽  
Otolith Growth ◽  
Two Stage ◽  
Orange Roughy ◽  
Mass Growth ◽  
Hoplostethus Atlanticus ◽  
Age Estimates ◽  
Radiometric Data

Ages of orange roughy (Hoplostethus atlanticus) determined by two methods (counting annuli on the surface of whole and in longitudinally sectioned otoliths) were similar up to maturity. Beyond maturity, age estimates from sectioned otoliths exceeded those from whole otoliths. Maximum recorded age was 125 years for an individual 41 cm standard length (SL), and age at maturity was estimated to be 25 years (30–32 cm SL). These are consistent with ages estimated previously by radiometric methods. Results demonstrated a two-stage linear relationship between otolith weight and age that confirmed the two-stage otolith mass growth model previously used in radiometric ageing. However, in the radiometric analyses the reduction in otolith growth was arbitrarily estimated at 45% of the immature rate whereas annuli data demonstrated a reduction after maturity to 62% of the immature rate. The new estimates of otolith mass growth rate were incorporated into the radiometric data and ages recalculated, which reduced age estimates for 38–40 cm SL fish from 77–149 to 59–101 years. The radiometric data were also recalculated using only the percentage reduction in otolith growth after maturity, giving the radiometric age of 125 ± 9 years for the oldest fish.

scholarly journals KEPADATAN STOK IKAN DEMERSAL DAN UDANG DI SAMUDERA HINDIA BARAT SUMATERA PADA MUSIM PERALIHAN II

2017 ◽  
Vol 22 (3) ◽  
pp. 139
Author(s):  
Nurulludin Nurulludin ◽  
Thomas Hidayat ◽  
Asep Mamun
Keyword(s):  
Indian Ocean ◽  
Demersal Fish ◽  
Catch Rate ◽  
Fish Stock ◽  
Fish Resources ◽  
The Indian Ocean ◽  
Density And Biomass ◽  
Swept Area ◽  
Average Catch ◽  
Stock Abundance

Kepadatan stok ikan merupakan indikasi dari potensi perikanan di suatu wilayah yang sangat penting diketahui. Tujuan tulisan ini membahas tentang laju tangkap, kepadatan stok dan perkiraan biomassa ikan demersal serta udang. Penelitian sumber daya ikan demersal dan udang di Samudera Hindia Barat Sumatera dilakukan dengan menggunakan Kapal Riset Baruna Jaya IV (1.200 GT) pada bulan Oktober dan November 2015 (Musim peralihan II). Penghitungan kepadatan stok menggunakan metode sweept area dengan panjang tali ris atas dari jaring trawl 36 m, kecepatan kapal saat menarik jaring berkisar 2,5 – 3 knot, lama penarikan jaring maksimal 1 jam. Perairan Samudera Hindia Barat Sumatera terdiri dari 151 spesies yang tergolong dalam 59 famili. Famili ikan demersal yang dominan tertangkap (5 besar), yaitu Leiognathidae sebesar 23,6 %, Trichiuridae 9,8%, Haemulidae 8,0%,  Engraulididae 6,6%, dan Polynemidae 6,05%. Famili udang yaitu Penaeidae (79,08%), Scyllaridae 19,49%, dan Solenoceridae 1,43%. Rata-rata laju tangkap ikan demersal 205,80 kg/jam, dengan kepadatan stok 6,66 ton/km2 dan udang 2,30 kg/jam dengan kepadatan stok 0,053 ton/km2. Biomassa ikan demersal diperkirakan sebesar 470.122 ton dan udang 3.706 ton.  Fish stock density  is an index of stock abundance indicating the fish resources potential in a region.  This paper discusses the catch rate, stock density and biomass estimates of the demersal fish and shrimp resources. Research on the demersal fish and shrimp resources in the Indian Ocean-Western Sumatera conducted using the Research Vessel Baruna Jaya IV (1200 GT) carried out during  October and November 2015 (2nd intermonsoon season). Stock density was estimated through the swept area method. The trawl used has 36 m headrope, trawling speed of 2.5 - 3 knots, and maximum towing time was 1 hour. It was found that the fish resources in the waters of the Indian Ocean-Western Sumatera consisted of 151 species belonging to 59 families. The top five dominant fish families caught were Leiognathidae of 23.6%, Trichiuridae 9.8%, Haemulidae 8.0%, Engraulididae 6.6%, and Polynemidae 6.05%, while the shrimp families were Penaeidae of 79.08%, Scyllaridae 19.49%, and Solenoceridae 1.43%. The average catch rate of demersal fish was 205.80 kg/hour, with a stock density of 6.66 tons/km2 and shrimp of 2.30 kg/hour with a stock density of 5.3 kgs/km2. The estimated biomass of demersal fish was  470,122 tons and shrimp was 3,706 tons.  

Folly and fantasy in the analysis of spatial catch rate data

2003 ◽  
Vol 60 (12) ◽  
pp. 1433-1436 ◽  
Author(s):  
Carl Walters
Keyword(s):  
Catch Rate ◽  
Population Trends ◽  
Rate Data ◽  
Fishing Activity ◽  
Time Period ◽  
Abundance Indices ◽  
Catch Rates ◽  
Catch Per Effort

Spatial catch per effort data can provide useful indices of population trends provided that they are averaged so as to correct for effects of changes in the distribution of fishing activity. Simple, nonspatial ratio estimates should not be used in such analyses. The averaging for any time period must necessarily make some assumptions about what catch rates would have been in spatial strata that had not yet, or were no longer, being fished. Ignoring the unfished strata (averaging only over the areas that were fished) amounts to assuming that they behaved the same as the fished strata and can lead to severe hyperdepletion in abundance indices for fisheries that developed progressively over large regions.

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