Simulating spatial dynamics to evaluate methods of deriving abundance indices for tropical tunas

2010 ◽  
Vol 67 (9) ◽  
pp. 1409-1427 ◽  
Author(s):  
Thomas R. Carruthers ◽  
Murdoch K. McAllister ◽  
Robert N. M. Ahrens
Keyword(s):  
Population Dynamics ◽  
Relative Abundance ◽  
Spatial Dynamics ◽  
Selection Criterion ◽  
Information Criterion ◽  
Fishing Effort ◽  
Catch Per Unit Effort ◽  
Applied Model ◽  
Thunnus Obesus ◽  
Abundance Indices

Relative abundance indices derived from nominal catch-per-unit-effort (CPUE) data are a principle source of information for the majority of stock assessments. A particular problem with formulating such abundance indices for pelagic species such as tuna is the interpretation of CPUE data from fleets that have changed distribution over time. In this research, spatial population dynamics are simulated to test the historical pattern of fishing effort as a basis for making inferences about relative abundance. A number of age-structured, spatially disaggregated population dynamics models are described for both Atlantic yellowfin tuna ( Thunnus albacares ) and bigeye tuna ( Thunnus obesus ) to account for uncertainty in spatial distribution and movement. These models are used to evaluate the reliability of standardization methods and a commonly applied model selection criterion, Akaike’s information criterion (AIC). The simulations demonstrate the pitfalls of aggregating CPUE data over spatial areas and highlight the need for data imputation. Simulations support simpler models than those selected using AIC for extracting reliable indices of relative abundance.

scholarly journals A Standardized Abundance Index from Fishery Independent Data: A Case Study of Swordfish (Xiphias Gladius) from Indonesian Tuna Longline Fishery

2020 ◽  
Vol 147 ◽  
pp. 02016
Author(s):  
Bram Setyadji ◽  
Zulkarnaen Fahmi
Keyword(s):  
Relative Abundance ◽  
Fishery Management ◽  
Negative Binomial ◽  
Stock Assessment ◽  
Information Criterion ◽  
Catch Per Unit Effort ◽  
Hurdle Models ◽  
Abundance Indices ◽  
Longline Fisheries ◽  
Tuna Longline

Most varieties of the billfish caught in the Indian Ocean are either swordfish or Indo-Pacific sailfish. Swordfish is mostly considered as by-catch from tuna longline fisheries, except for South African, Spanish and Portuguese fleets. Despite of its importance, little are known about their abundance. Relative abundance indices are the input data for stock assessment analyses that provide useful information for decision making and fishery management. In this paper, a Generalized Linear Model (GLM) was utilized to systematize the catch-per-unit-effort (CPUE) and to estimate relative abundance indices based on the Indonesian longline dataset. The data was collected by scientific observers from August 2005 to December 2016. Conventional models for counting data were used, but zero-inflated and hurdle models also considered, due to the high number of zero-catchper-set. Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) were applied to select the best models among all those evaluated. Both AIC and BIC suggested that the simple negative binomial (NB) model is the best option. The trends were relatively similar to the nominal series, but with smoother peaks. In general, there was a tendency of positive trends in the last decade, with the series varying throughout the period.

scholarly journals Factors affecting relative abundance of low-mobility fishing resources: spiny lobster in the Galapagos Marine Reserve

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7278 ◽  
Author(s):  
Juan Carlos Murillo-Posada ◽  
Silvia Salas ◽  
Iván Velázquez-Abunader
Keyword(s):  
Monitoring System ◽  
Relative Abundance ◽  
Spatial Scales ◽  
Marine Reserve ◽  
Spiny Lobster ◽  
Fishing Effort ◽  
Additive Models ◽  
Catch Per Unit Effort ◽  
Monthly Basis ◽  
Galapagos Marine Reserve

Management of low-mobility or benthic fisheries is a difficult task because variation in the spatial distribution and population dynamics of the resources make the monitoring and assessment of these fisheries challenging. We assumed that environmental, spatial, and temporal factors can contribute to the variability of the relative abundance of such species; we used Generalized Additive Models for Location Scale and Shape (GAMLSS) to test this hypothesis using as a case study the lobster fishery (targeting two species) in the Galapagos Marine Reserve, Ecuador. We gathered data on each of the two species of lobster on a monthly basis over seven years, including: (a) onboard observers’ records of catch data, fishing effort, and ground location by trip, and (b) data from interviews undertaken with fishers at their arrival to port, recording the same type of information as obtained from onboard observers. We use this information to analyze the effect of the measured variables and to standardize the Catch per Unit Effort (CPUE) in each case, using the GAMLSS. For both species, the temperature, region, fishing schedule, month, distance, and the monitoring system were significant variables of the selected models associated with the variability of the catch rate. ForPanulirus penicillatus, CPUE was higher at night than during the day, and forPanulirus gracilisit was higher during the day. Increased temperature resulted in a decrease of CPUE values. It was evident that temporal, spatial scales and monitoring system can influence the variability of this indicator. We contend that the identification of drivers of change of relative abundance in low-mobility species can help to support the development of monitoring and assessment programs for this type of fisheries.

Does habitat or depth influence catch rates of pelagic species?

2007 ◽  
Vol 64 (11) ◽  
pp. 1581-1594 ◽  
Author(s):  
Keith A Bigelow ◽  
Mark N Maunder
Keyword(s):  
Relative Abundance ◽  
Environmental Conditions ◽  
Environmental Data ◽  
Catch Per Unit Effort ◽  
Blue Shark ◽  
Species Vulnerability ◽  
Thunnus Obesus ◽  
Catch Rates ◽  
The Relationship ◽  
The Vertical Distribution

The efficiency of a pelagic longline fishing operation and the species composition of the resulting catch is influenced primarily by the relationship between the distribution of hooks and species vulnerability, with vulnerability described by either depth or some suite of environmental variables. We therefore fitted longline catch rate models to determine whether catch is estimated better by vertically distributing a species by depth or by environmental conditions (e.g., temperature, thermocline gradient, and oxygen concentration). Catch rates were estimated by two methods: (i) monitoring longlines where the vertical distribution of hooks and catch in relation to depth and environmental conditions is known, and (ii) applying a statistical habitat-based standardization (statHBS) model to fishery and environmental data to develop relative abundance indices for bigeye tuna (Thunnus obesus) and blue shark (Prionace glauca). Results indicated that an understanding of gear dynamics and environmental influences are important for analyzing catch-per-unit-effort (CPUE) data correctly. Analyses based on depth-specific catch rates can lead to serious misinterpretation of abundance trends, despite the use of sophisticated statistical techniques (e.g., generalized linear mixed models). This illustrates that inappropriate inclusion or exclusion of important covariates can bias estimates of relative abundance, which may be a common occurrence in CPUE analysis.

scholarly journals Comparación entre dos modelos estructurados por edades, aplicados a la pesquería de langosta, Panulirus Argus (Latreille, 1804), en la región suroriental de Cuba

2012 ◽  
Vol 3 ◽  
pp. 131
Author(s):  
Romina Alzugaray Martínez ◽  
Rafael Puga Millán
Keyword(s):  
Linear Models ◽  
Population Analysis ◽  
Spiny Lobster ◽  
Information Criterion ◽  
Fishing Effort ◽  
Panulirus Argus ◽  
Catch Per Unit Effort ◽  
Raw Data ◽  
Linear Relationships ◽  
Exploitation Status

La langosta común, Panulirus argus, es una de las especies con mayor valor comercial en el Atlántico Centro Occidental. En Cuba se han realizado numerosos estudios para conocer y actualizar su estado de explotación y recomendar medidas de manejo. A pesar de estas medidas, las capturas continúan disminuyendo, por lo que el objetivo del presente estudio consistió en evaluar la dinámica de la población de langosta en la región suroriental de Cuba, a través de dos estrategias analíticas diferentes. A partir de datos de captura y esfuerzo pesquero de 1979-2010, se aplicaron un análisis de población virtual (VPA) y un análisis estadístico de captura por edades (SCA). Se examinó la relación lineal entre los datos primarios y las variables estimadas por los modelos. El ajuste de los modelos lineales de los datos se evaluó mediante el Criterio de Información de Akaike corregido (AICc). Según ambos métodos de captura por edades, el tamaño poblacional y el reclutamiento de langostas con un año de edad han disminuido en la región en el período estudiado, aunque el SCA muestra estabilización en la última década. Mientras, la biomasa poblacional disminuyó hasta estabilizarse en la última década, lo cual puede relacionarse con el comportamiento histórico de la captura por unidad de esfuerzo. Existen asociaciones lineales significativas entre los datos primarios y las variables estimadas. Según los valores de Δi, el modelo VPA garantiza el mejor ajuste de las variables a las relaciones lineales estimadas. Abstract Spiny lobster, Panulirus argus, is one of the most commercially valuable species in the Western Central Atlantic. Although numerous studies have been conducted in Cuba to learn and update its exploitation status and to recommend management measures, catches continue to decline. Consequently, the objective of this study was to evaluate the dynamics of the lobster population in Cuba’s southeastern region, through two different analytical strategies. Using catch and fishing effort data from 1979-2010, a Virtual Population Analysis (VPA) and a Statistical Catch-at-age Analysis (SCA) were applied. We examined the linear relationship between raw data and the variables estimated by the models. The fit of the linear models to data was assessed using the corrected Akaike Information Criterion (AICc). According to both age-structured methods, population size and recruitment of one year old lobster have declined in the region during the study period, although the SCA shows stabilization in the last decade. Population biomass decreased to stabilize in the last decade, this may relate to the historical behavior of the catch per unit effort. There are significant linear associations between raw data and estimated variables. According to Δi values, the VPA model ensures the best fit for the variables of estimated linear relationships.

Hierarchical analysis of multiple noisy abundance indices

2010 ◽  
Vol 67 (1) ◽  
pp. 108-120 ◽  
Author(s):  
Paul B. Conn
Keyword(s):  
Relative Abundance ◽  
Sampling Error ◽  
Atlantic Coast ◽  
Implicit Assumption ◽  
Hierarchical Analysis ◽  
Catch Per Unit Effort ◽  
Spanish Mackerel ◽  
Process Error ◽  
The Us ◽  
Abundance Indices

Fisheries analysts often rely on relative abundance indices for assessing stock status. However, trends in abundance can be difficult to discern when there are multiple indices or when correlation among indices is weak or negative. In this paper, I present a hierarchical framework for analyzing multiple, noisy indices with the goal of estimating a single time series of relative abundance. An implicit assumption is that each index is measuring the same quantity (relative abundance) but that each is subject to process error (attributable to variation in catchability, spatial distribution, etc.) in addition to an estimable level of within-survey variance (i.e., sampling error). I use simulation to explore estimator performance under a number of scenarios, including several that violate underlying assumptions. In general, the hierarchical approach produced estimators with reasonable properties. I illustrate the method with an analysis of seven fishery-dependent catch-per-unit-effort indices of Spanish mackerel ( Scomberomorus maculatus ) off the US Atlantic coast and provide several suggestions for how this approach can be used in practice.

scholarly journals Population dynamics and CPUE of Alosa genus with emphasis on Alosa braschnikovi (Borodin, 1904) on the coasts of Golestan Province, Iran

2018 ◽  
Vol 19 (1) ◽  
pp. 59-66
Author(s):  
ZOBEYDE BIBAK ◽  
SEYYED YOUSEF PAIGHAMBARI ◽  
MOJTABA POULADI ◽  
RASOUL GHORBANI ◽  
SEYYED ABBAS HOSSEINI ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Sex Ratio ◽  
Relative Abundance ◽  
Fish Species ◽  
Age Groups ◽  
Abundant Species ◽  
Catch Per Unit Effort ◽  
Beach Seine ◽  
Unit Effort ◽  
Golestan Province

Bibak Z, Paighambari SY, Pouladi M, Ghorbani R, Hosseini SA, Yahyaei M. 2018. Population dynamics and CPUE of Alosa genus with emphasis on Alosa braschnikovi (Borodin, 1904) on the coasts of Golestan Province, Iran. Biodiversitas 19: 59-66. The aim of this study was to compare relative abundance and catch per unit effort of members of the Alosa genus (family: Clupeidae) in the fishing grounds of Gomishan and Miankale in Golestan coasts. Sampling operations were done by beach seine during 2011 to 2012. A total of 240 fish were collected. Identified species in Gomishan were: Alosa braschnikovi (Borodin, 1904) and A. saposchnikovi (Grimm, 1887). The most abundant species in this region were individuals of A. braschnikovi. The highest length and weight in the region were 35.6±1.85 mm and 447.8±57.43 gr for Alosa braschnikovi in Gomishan. Besides the two mentioned species, A. kessleri (Grimm, 1887) was caught in Miankale coasts. The most abundant species again was Alosa braschnikovi in this region. The highest length and weight were 33.12±3.18 cm and 362.5±99.57 gr for Alosa braschnikovi in Miankale region. The results showed that mean of CPUE in Miankale was higher than in the Gomishan region. The comparison of sex ratio for shads showed that males were dominant against females. Also, the comparison between species showed that the highest values for length, and weight of fish species compared belonged to Alosa braschnikovi. Among the Alosa braschnikovi fishes caught, individuals were in the range of 2 to 5 age groups within the two compared regions and most abundant were observed in 4 age groups.

scholarly journals THE INFLUENCE OF THE COASTAL CURRENT ON THE ESTIMATION OF RELATIVE ABUNDANCE INDICES IN SMALL-SCALE SHRIMP FISHERY

2021 ◽  
Vol 47 ◽  
pp. e665
Author(s):  
Paulo Victor do Nascimento ARAÚJO ◽  
Alex Barbosa de MORAES ◽  
Flávia LUCENA FRÉDOU ◽  
Fúlvio Aurélio de Morais FREIRE
Keyword(s):  
Relative Abundance ◽  
Stock Assessment ◽  
Northeastern Brazil ◽  
Small Scale ◽  
Coastal Current ◽  
Sampling Effort ◽  
Catch Per Unit Effort ◽  
Abundance Index ◽  
Shrimp Fishery ◽  
Abundance Indices

The aim of this scientific note was to evaluate the influence of the coastal current on the estimation of relative abundance indices for small-scale marine shrimp trawling to indicate the best relative abundance index to be used for stock assessment and conservation. Georeferenced experimental trawls were carried out with standardized equipment and capture time on the coast of Rio Grande do Norte, northeastern Brazil. Drags followed convergent and divergent orientations in relation to the flow of the local coastal current. The results showed that the direction of the coastal current flow directly influences the distances and drag shifts, generating variations in the sampling effort and, consequently, bias when using Catch per Unit Effort (CPUE) as a relative abundance index. Conversely, the adoption of Catch per Unit of Swept Area (CPUA) as an index of relative abundance for shrimp trawling becomes more suitable since the variations in the distances of trawl shifts are perceptible through this index.

scholarly journals Impacts of the live reef fish trade on populations of coral reef fish off northern Borneo

2007 ◽  
Vol 274 (1612) ◽  
pp. 989-994 ◽  
Author(s):  
Helen Scales ◽  
Andrew Balmford ◽  
Andrea Manica
Keyword(s):  
Coral Reef ◽  
Reef Fish ◽  
Relative Abundance ◽  
Coral Reef Fish ◽  
Fishing Effort ◽  
Catch Per Unit Effort ◽  
Future Data ◽  
Large Coral ◽  
Species Specific ◽  
Fish Trade

The live reef fish trade (LRFT) is one of the greatest but least-quantified sources of fishing pressure for several species of large coral reef fish across the Indo-Pacific. For the first time we quantify the localized impact of the LRFT. We collected data from three LRFT traders in northern Borneo, which yielded information on daily fishing effort and the species and mass of all fishes sold every day by individual fishers or vessels over 2, 3 and 8 years. Total monthly catch and relative abundance (catch-per-unit-effort) declined significantly in several species, including the most valuable species the Napoleon wrasse ( Cheilinus undulatus , estimated changes of −98 and −78% over 8 years in catch and relative abundance, respectively) and lower-value bluelined groupers ( Plectropomus oligocanthus : −99 and −81%) and Epinephelus groupers (−89 and −32%). These severe declines were rapid, species-specific and occurred in the first 2–4 years of the dataset and are, we believe, directly attributable to the LRFT. This has crucial implications for future data collection and monitoring if population collapses in other parts of the LRFT and similar wildlife trades are to be successfully detected.

scholarly journals Quantifying the increase in fishing efficiency due to the use of drifting FADs equipped with echosounders in tropical tuna purse seine fisheries

2020 ◽  
Author(s):  
Gwenaëlle Wain ◽  
Loreleï Guéry ◽  
David Michael Kaplan ◽  
Daniel Gaertner
Keyword(s):  
New Technology ◽  
Recent Change ◽  
Purse Seine ◽  
Catch Per Unit Effort ◽  
Katsuwonus Pelamis ◽  
Thunnus Obesus ◽  
Efficiency Increase ◽  
Tropical Tuna ◽  
Floating Objects ◽  
The Impact

Abstract Numerous pelagic species are known to associate with floating objects (FOBs), including tropical tunas. Purse seiners use this behaviour to facilitate the capture of tropical tunas by deploying artificial drifting fish aggregating devices (dFADs). One major recent change has been the integration of echosounders in satellite-tracked GPS buoys attached to FOBs, allowing fishers to remotely estimate fishable biomass. Understanding the effects of this new technology on catch of the three main tuna species (yellowfin tuna, Thunnus albacares; bigeye tuna, Thunnus obesus; and skipjack tuna, Katsuwonus pelamis) is important to accurately correct for this change in catch-per-unit-effort (CPUE) indices used for stock assessments. We analysed catch data from the French purse seine fleet for the period 2010–2017 in the Indian Ocean to assess the impact of this fleet’s switch to echosounder buoys around 2012. Results indicate that echosounders do not increase the probability a set will be succesful, but they have a positive effect on catch per set, with catches on average increasing by ≈2−2.5 tonnes per set (≈10%) when made on the vessel's own dFADs equipped with an echosounder buoy. Increases were due to a decrease in sets below ≈25 tonnes and an increase in those greater than ≈25 tonnes, with a non-linear transition around this threshold. This increase explains the considerable investment of purse seiners in echosounder buoys, but also raises concerns about bias in stock size estimates based on CPUE if we do not correct for this fishing efficiency increase.

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