CAtch rate Standardisation of fin-fishes targeted by the GAlician (NW Spain) Small-Scale fishery

The principal aim of this study is to standardize catch and effort data obtained from observers on commercial fishing vessels for a number of finfish species targeted by the small-scale (1) fishing fleet off the Galician coast (ICES areas IXa and VIIIc). This would allow the development of indices of abundance to be used as inputs for stock assessments. A secondary objective is to investigate the degree of synchronicity among trends in species’ abundance in relation to environmental conditions and life history traits.

The proposal builds on various pillars of the current ICES strategic plan. It specifically seeks for an understanding of the dynamics and structure of key biotic components from an integrated perspective (Goals 1 and 2). It also fosters the use of sound statistical models to analyze new data sets (Goals 4), and provide credible advice for management needs (Goal 3).
ICES Science Fund should support this proposal according to the following reasoning: i) small-scale fisheries have a strong socio-ecological importance for the region and are understudied [1], ii) they are of interest within the Common Fisheries Policy (CFP) debate [2], and iii) ICES has manifested the importance of gathering information for species subjected to exploitation in EU coastal waters though not included in management plans yet [3].
The aim of standardization is to obtain indices of relative abundance once removed the impact on catch rates of factors other than abundance [4]. These indices can be later used to feed assessment models in order to provide reliable advice. This method is frequently used to study large pelagics stocks, mainly sharks and tunas (e.g. [5-7]) for which fishery-independent data is non-existent, though rarely used for other species (but see [8]).
Fishery data is usually non Gaussian and errors not independent in time and/or space, thus there is a need to use appropriate statistical methods to provide robust time series of abundance. To this end, we will explore the use of several models including generalized linear models (GLMs), generalized additive models (GAMs), mixed modelling (GLMMs and GAMMs), so as zero-inflated models (ZI) that allow the accommodation of null samples [9-11].
The Galician small-scale fishery is a multi-species and multi-gear fishery that, despite its importance, lacks of robust management plans. The governmental agency UTPB (“Technical Unit of Artisanal Fisheries”) runs a monitoring fishery-dependent program since mid-1990s that serves the autonomous government (“Xunta de Galicia”) to develop simple exploitation plans together with the several fisheries associations (“Cofradías”). However, these data have never been further used outside the regional domain, thus we consider the information an unique source to apply advanced statistical tools for robust standardization of abundance and deliver the results to the assessment and management bodies. Briefly, data are recorded by UTPB observers onboard fishing vessels randomly selected within the artisanal fleet. This sampling is assumed to be random within the commercial catch and well balanced among the set of numerous gears, seasons and with a sufficient spatial coverage. The usage of this information is in its first steps and, to date, relegated to two species [12-15]. The proposal, however, is focused on analysing at least a set of 12 species of equal interest for both the government and ICES. These will comprise the following: i) a number of species requested by the WGHMM [3] including the seabass (Dicentrarchus labrax), the gunnar (Eutrigla gurnardus), the plaice (Pleuronectes platessa), the pollack (Pollachius pollachius), the sole (Solea vulgaris), and the red mullet (Mullus surmuletus); and ii) a list of six other abundant and valuable species including the white seabream (Diplodus sargus), the pouting (Trisopterus luscus), the ballan wrasse (Labrus bergylta), the european conger (Conger conger), the undulate ray (Raja undulata), and the small-spotted catshark (Scyliorhinus canicula). Overall, this set of species covers a wide range of different taxa of the coastal fish community in the area. However, we would like to note that during the kick off meeting (held in Santiago de Compostela on 28th April 2014) we decided to make a few changes in the selected set of species (see casgass_species).

Oficial web page of the project.

(1)   We here define the small-scale fleet as those vessels that are smaller than 18 m length and 50 GRT that operate in coastal waters. Excluded are offshore trawlers and seiners.

Scientists involved in the CASGASS project:

Alexandre Alonso Fernández, lead applicant, academic scientist: data analysis and model development, IIM-CSIC
Rafael Bañón, co-applicant, government scientist: data handling and management purposes, UTPB-Xunta de Galicia
Jaime Otero Villar, academic scientist staff: data analysis and model development, IIM-CSIC
Xosé Antón Álvarez Salgado, academic scientist staff: data analysis and model development, IIM-CSIC
Jose Manuel Campelos, government scientist staff: data handling and management purposes, UTPB-Xunta de Galicia
Fernando Quinteiro Fernandez, government scientist staff: data handling and management purposes, UTPB-Xunta de Galicia


Press release

  • Press 14/06/2014

Atlántico Diario 14/06/2014 (online)

  • Radio interview

Since 25′ (in Galician) 12/06/2014



[1]      Freire J & García-Allut A (2000) Socioeconomic and biological causes of management failures in European artisanal fisheries: the case of Galicia (NW Spain). Marine Policy 24: 375–384.


[3]      ICES (2013) Report of the Working Group on the Assessment of Southern Shelf Stocks of Hake, Monk, and Megrim (WGHMM), 10 – 16 May 2013, ICES Headquarters, Copenhagen. ICES CM 2013/ACOM:11A, 11 p.

[4]      Maunder MN & Punt AE (2004) Standardizing catch and effort data: a review of recent approaches. Fisheries Research 70: 141–159.

[5]      Baum JK & Blanchard W (2010) Inferring shark population trends from generalized linear mixed models of pelagic longline catch and effort data. Fisheries Research 102: 229–239.

[6]      Minami M, Lennert-Cody CE, Gao W & Román-Verdesoto M (2007) Modeling shark bycatch: The zero-inflated negative binomial regression model with smoothing. Fisheries Research 84: 210–221.

[7]      Brodziak J & Walsh WA (2013) Model selection and multimodel inference for standardizing catch rates of bycatch species: a case study of oceanic whitetip shark in the Hawaii-based longline fishery. Canadian Journal of Fisheries and Aquatic Sciences 70: 1723–1740.

[8]      Battaile BC & Quinn II TJ (2004) Catch per unit effort standardization of the eastern Bering Sea walleye pollock (Theragra chalcogramma) fleet. Fisheries Research 70: 161–177.

[9]      McCullagh P & Nelder JA (1989) Generalized Linear Models. Chapman & Hall, London, UK.

[10]  Wood S (2006) Generalized Additive Models: An Introduction with R. Chapman & Hall, London, UK.

[11]  Zuur AF, Saveliev AA, Ieno EN (2012) Zero Inflated Models and Generalized Linear Mixed Models with R. Highland Statistics Ltd., Newburgh, UK.

[12]  Villegas-Ríos D, Alonso-Fernández A, Fabeiro M, Bañón R & Saborido-Rey F (2013) Demographic variation between colour patterns in a temperate protogynous hermaphrodite, the ballan wrasse Labrus bergylta. PLoS One 8: e71591.

[13]  Villegas-Ríos D, Alós J, Palmer M, Lowerre-Barbieri S, Bañón R, Alonso-Fernández A & Saborido-Rey F (in review) Fish life-history shapes catchability. Journal of Applied Ecology.

[14]  Alonso-Fernández A, Otero J, Villegas-Ríos D & Bañón R (in review) Drivers of body size changes of a Pollachius pollachius stock in NE Atlantic coastal waters. Marine Ecology Progress Series.

[15]  Otero J, Alonso-Fernández A, Villegas-Ríos D & Bañón R (in preparation) Standardising trends in catch rates of Pollachius pollachius harvested by the small-scale fishery along the Galician coast (NE Atlantic). ICES Journal of Marine Science.

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