scholarly journals Inferring the depth distribution of catchability for pelagic fishes and correcting for variations in the depth of longline fishing gear

2005 ◽  
Vol 62 (5) ◽  
pp. 1130-1142 ◽  
Author(s):  
Peter Ward ◽  
Ransom A Myers
Keyword(s):  
Time Series ◽  
Depth Distribution ◽  
Fishing Gear ◽  
Commercial Catch ◽  
Additional Information ◽  
Pelagic Fishes ◽  
The Pacific ◽  
Abundance Indices ◽  
The Pacific Ocean ◽  
Catch Rates

We introduce a new method that uses generalized linear mixed models to infer the depth distribution of pelagic fishes. It uses existing data from research surveys and observers on commercial vessels to estimate changes in catchability when longline fishing gear is lengthened to access deeper water. We infer the depth distribution of catchability for 37 fish species that are caught on pelagic longlines in the Pacific Ocean. We show how the estimates of catchability can be used to correct abundance indices for variations in longline depth. Our method facilitates the inclusion of data from early surveys in the time series of commercial catch rates used to estimate abundance. It also resolves inconsistencies in the time series caused by a rapid switch to deep longlining in the 1970s. The catchability distribution does not always match depth preferences derived from tracking studies. Therefore, depth preferences from tracking studies should not be used to correct abundance indices without additional information on feeding behavior.

How reliable are the abundance indices derived from commercial catch–effort standardization?

2009 ◽  
Vol 66 (7) ◽  
pp. 1169-1178 ◽  
Author(s):  
Yimin Ye ◽  
Darren Dennis
Keyword(s):  
Generalized Linear Model ◽  
Observation Error ◽  
Potential Bias ◽  
Catch Per Unit Effort ◽  
Rock Lobster ◽  
Commercial Catch ◽  
Abundance Indices ◽  
Catch Rates ◽  
Power Component ◽  
Stock Abundance

Commercial catch-per-unit-effort (CPUE) data are often standardized to construct indices of stock abundance. The value of such standardization lies in the improvement in the proportionality between the derived index and true abundance. Using the Torres Strait rock lobster ( Panulirus ornatus ) fishery in Australia as an example, we first standardized the commercial CPUE data using a generalized linear model (GLM) and then fitted observation error models to the resulting abundance indices and independent abundance data (as estimated by research diver surveys) to examine the proportionality. While the GLM standardization greatly improved proportionality in comparison with the nonstandardized commercial catch rates, it could produce biased results if the model did not explicitly incorporate variables that had caused changes in fishing efficiency. As most catch–effort standardizations do not model the fishing power component simultaneously, this result may serve as a warning to the potential bias in stock abundance indices extracted from GLMs that are underfitted.

Estimating abundance of pelagic fishes using gillnet catch data in data-limited fisheries: a Bayesian approach

2007 ◽  
Vol 64 (7) ◽  
pp. 1019-1033 ◽  
Author(s):  
Shane P Griffiths ◽  
Petra M Kuhnert ◽  
William N Venables ◽  
Stephen J.M Blaber
Keyword(s):  
Effective Area ◽  
Similar Species ◽  
Ecosystem Models ◽  
Tropical Regions ◽  
Catch Data ◽  
Pelagic Fishes ◽  
Abundance Estimates ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Ecosystem Based Fisheries Management

We describe a Bayesian modelling approach to estimate abundance and biomass of pelagic fishes from gillnet catches in data-limited situations. By making a number of simple assumptions, we use fish sustained swimming speed to calculate the effective area fished by a gillnet in a specified soak time to estimate abundance (fish·km–2) from the number of fish caught. We used catch data from various sampling methods in northern Australia and elicited anecdotal information from experts to build a size distribution of the true population to compensate for size classes that were unlikely to be represented in the catch because of size selectivity of the gear. Our final abundance estimates for various-sized scombrids (0.04–4.17 fish·km–2) and istiophorids (0.004–0.005 fish·km–2) were similar to what has been estimated for similar species in more data-rich situations in tropical regions of the Pacific Ocean. The model is particularly useful in data-limited situations in which abundance or biomass estimates are required for pelagic fish species of low economic importance. These data are often required for ecosystem models (e.g., Ecopath) that are increasingly being considered as potential tools for ecosystem-based fisheries management.

Systematics of the genus Halgerda Bergh, 1880 (Heterobranchia : Nudibranchia) of Mozambique with descriptions of six new species

2018 ◽  
Vol 32 (6) ◽  
pp. 1388
Author(s):  
Yara Tibiriçá ◽  
Marta Pola ◽  
Juan Lucas Cervera
Keyword(s):  
New Species ◽  
Indian Ocean ◽  
Western Indian Ocean ◽  
Molecular Data ◽  
Colour Variation ◽  
Additional Information ◽  
Species Complexes ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Pseudocryptic Species

The species of the genus Halgerda Bergh, 1880, are restricted to the Indo-Pacific; some being common inhabitants of reefs off the coast of Mozambique. These species have been relatively well studied morphologically, but few molecular data are available. During a seven-year period surveying the reefs of Mozambique, 11 Halgerda spp. were collected, six of which are described here. We provide details on their morphology, anatomy, novel genetic markers and additional information about their colour variation. The new species described herein are Halgerda leopardalis, sp. nov., H. mozambiquensis, sp. nov., H. jennyae, sp. nov., H. meringuecitrea, sp. nov., H. nuarroensis, sp. nov. and H. indotessellata, sp. nov., the last of which was found to be a pseudocryptic species of H. tessellata. Moreover, we identified two species complexes, one composed mainly of specimens from the Western Indian Ocean and another with specimens mostly from the Pacific Ocean and Western Australia.

scholarly journals Investigating links between rainfall variations in the Ogooué River basin and ENSO in the Pacific Ocean over the period 1940–1999

2021 ◽  
Vol 384 ◽  
pp. 181-186
Author(s):  
Sakaros Bogning ◽  
Frédéric Frappart ◽  
Gil Mahé ◽  
Adrien Paris ◽  
Raphael Onguene ◽  
...  
Keyword(s):  
Time Series ◽  
Pacific Ocean ◽  
River Basin ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
The Pacific ◽  
Basin Scale ◽  
The Pacific Ocean ◽  
Wavelet Coherence Analysis ◽  
Enso Index

Abstract. This paper investigates links between rainfall variability in the Ogooué River Basin (ORB) and El Niño Southern Oscillation (ENSO) in the Pacific Ocean. Recent hydroclimatology studies of the ORB and surrounding areas resulting in contrasting conclusions about links between rainfall variability and ENSO. Thus, to make the issue clearer, this study investigates the links between ENSO and rainfall in the ORB over the period 1940–1999. The principal component analysis of monthly rainfall in the ORB was done. The temporal mode of the first component corresponds to the interannual variations of rainfall on the ORB. Also, the pattern of the spatial mode of the first component shows that the ORB is a homogeneous hydroclimatic zone. However, no leading mode is significantly correlated to the ENSO index. A cross-wavelet analysis of the time series of basin-scale rainfall and the ENSO index was therefore carried out. The result is a set of periodogram structures corresponding to some ENSO episodes recorded over the study period. And wavelet coherence analysis of both time series confirms that there are significant links between ENSO and rainfall in the ORB.

scholarly journals Observation of equatorial Kelvin solitary waves in a slowly varying thermocline

1998 ◽  
Vol 5 (3) ◽  
pp. 153-165 ◽  
Author(s):  
Q. Zheng ◽  
R. D. Susanto ◽  
X.-H. Yan ◽  
W. T. Liu ◽  
C.-R. Ho
Keyword(s):  
Time Series ◽  
Dispersion Relation ◽  
Solitary Waves ◽  
Nonlinear Term ◽  
Equatorial Pacific ◽  
Equatorial Waves ◽  
Kelvin Wave ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Dispersive Term

Abstract. TOPEX/POSEIDON (T/P) sea level deviation (SLD) time series from 3 October 1992 to 15 May 1997 combined with upper ocean thermal structures are used to observe the characteristics and analyze the dynamics of equatorial waves in the Pacific Ocean. The evolution of the Kelvin wave propagating along an eastward shoaling thermocline in the equatorial Pacific is investigated. The behaviour of this wave as it propagates eastward can be approximately described with the solutions of the perturbed Korteweg-de Vries (PKDV) equation and modified Green's Law. Assuming that the nonlinear term and dispersive term of this equation are balanced, the amplitude increases as the thermocline decreases to the power -3/8. Approaching the eastern Pacific, the nonlinearity increases and the relation changes to the power -9/8. The dispersion relation, and mass and energy conservations are investigated. The results indicate that under a varying thermocline, the nonlinear Kelvin solitary waves indeed exist in the real ocean.

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