Yorgos Stratoudakis

Instituto Português do Mar e da Atmosfera | IPMA · Divisão de Modelação e Gestão de Recursos de Pesca

The Marine Stewardship Council (MSC) is the frontrunner in fisheries certification, receiving both exten-sive support and strong criticisms. The increasing uptake by fisheries and markets (almost 10% of worldfisheries tonnage engaged by the end of 2014) has been followed by a widening pool of stakeholdersinteracting with the MSC. However, the appli...

To provide new information on the ingress dynamics of glass eels at the Portuguese coast, the study analyzes catch per unit effort (CPUE) data from river Lis, biometric data from recruits in basins of western Portugal and meteo-oceanographic data from the Iberian margin and shelf. Biometric data of glass eels in western Portugal are congruent with...

Converting assemblages of marine protected areas (MPAs) into functional MPA networks requires political will, multidisciplinary information, coordinated action and time. We developed a new framework to assist planning environmental representativity in a network across the marine space of Portugal, responding to a political commitment to protect 14%...

Fisheries co-management policy and research have been extensively reported in recent decades, with mixed results in process and outcome. Co-management has proliferated worldwide under the assumption that fisher participation in resource regimes enhances authority of decisions, reduces transaction costs, and increases compliance. The concept of legi...

Anadromous fish challenge human jurisdictions and are exposed to cumulative pressures originating in the marine, freshwater, and terrestrial realms. Here, a detailed questionnaire survey to anadromous fishers (river Mondego, n = 35; international river Minho/Miño, n = 38) assesses and compares perceptions on sustainability and management for import...

The glass eel catch from the international River Minho, western Iberian Peninsula, forms the southernmost Atlantic series in the composite index outside the North Sea assessing European eel recruitment. Here, new experimental yield data from the lower estuary (1981–2022) and fishers´ daily records (1990–2022) were modelled to describe and compare s...

Passive acoustic monitoring (PAM) is useful for monitoring vocal fish but has had so far limited application in fisheries management. Here, four years (2016–2019) of concurrent daily catch and effort fishery data in Portugal and species-specific vocal activity in the Tagus estuary are compared to describe biological and small-scale fishery dynamics...

Costa de Caparica and Fonte da Telha are oceanic communities southwards of Lisbon founded by fishers targeting pelagic fish by beach seining (Arte-Xávega). This chapter aims to capture fishers’ environmental knowledge, practices and adaptations over the past century and compare between the two sites. Livelihood interviews and questionnaires provide...

Este relatório descreve o trabalho de campo e sintetiza os resultados de um inquérito realizado com os pescadores profissionais de peixes anádromos no Troço Internacional do Rio Minho/Miño (TIRM) durante 2021. O objetivo do inquérito foi de recolher individualmente e sistematizar a opinião dos pescadores perante uma proposta de alteração do ordenam...

This report summarizes current threats to the Tagus estuary and adjacent ecosystems, presented in Lisbon in June 2021, and prioritizes actions to maintain or improve ecosystem services for a densely populated area close to the deep ocean.

Seafood certification in developing countries

River defragmentation works and an effective fishway with a monitoring station have created conditions for adaptive fishery management in the estuary of Mondego River in central Portugal. Since 2013 fishers, scientists and authorities annually meet to update data for anadromous fish and rules for the upcoming fishing season. Meetings provide an opp...

Collective engagement and inclusiveness have been in growing demand particularly within the context of managing natural resources. Here, a natural and a social scientist report on a case that the two have participated over the past decade, supported by a transdisciplinary evaluation framework. With the aid of a boundary scientist external to the pr...

Human population on Earth at the start of the Neolithic was approximately equal to the current population of the metropolitan Lisbon area. In the last ten thousand years human population on Earth increased three orders of magnitude and its use of energy and materials increased five orders. This was achieved though novel mechanisms of harnessing fre...

The Marine Stewardship Council (MSC) is the frontrunner in fisheries certification, receiving both extensive support and strong criticisms. The increasing uptake by fisheries and markets (almost 10% of world fisheries tonnage engaged by the end of 2014) has been followed by a widening pool of stakeholders interacting with the MSC. However, the appl...

The project MAIA (Marine Protected Areas in the Atlantic arc) provided an opportunity to address the problems of fishery data quality within an MPA (Luíz Saldanha Marine Park – PMLS) through a partnership between fishers and scientists. The long-term goals of this partnership were to reinforce the trust among stakeholders, improve accuracy in catch...

This contribution summarizes the main concerns presented by experts at a conference held in Lisbon in January 2015 to discuss the developing Portuguese legal framework for MSP and lists the suggestions that were correspondingly offered on how to improve the proposed framework.

The Prof. Luiz Saldanha Marine Park (PMLS – Arrábida, Portugal) was created in 1998 and has been managed according to a spatial plan since 2005. This study presents the results from an inquiry on the perceptions of PMLS users in relation to the ecological, socioeconomic and governance situation in the Park 4-7 years after the phased implementation...

The Prof. Luiz Saldanha Marine Park (PMLS - Arrábida, Portugal) was created in 1998 and is regulated by a spatial plan since 2005 (POPNA). The present study shows results from an inquiry that collected information and opinions of PMLS fishers on the ecological, socio-economic and governance conditions 4-7 years after the phased introduction of regu...

The behavioural effects of confinement of sardine Sardina pilchardus in a purse seine were evaluated through three laboratory experiments simulating the final stages of purse seining; the process of slipping (deliberately allowing fishes to escape) and subsequent exposure to potential predators. Effects of holding time (the time S. pilchardus were...

We present a method for estimating the interspawning interval (ISI) in batch-spawning teleosts with indeterminate fecundity based on the rate of oocyte growth and the size of oocytes at the beginning and end of the spawning cycle. The method is accompanied by a number of prerequisites, which are tested and subsequently applied to wild collections o...

Cetaceans are known to interact with numerous fisheries in many parts of the world resulting sometimes in detrimental effects for the animals (by catch and incidental mortality) and the fishery (reduction of catches, increasing fishing time, loss of gear, depredation). In Portugal, four of the 19 species of cetaceans found in continental waters ove...

Bernal, M., Stratoudakis, Y., Wood, S., Ibaibarriaga, L., Uriarte, A., Valdés, L., and Borchers, D. 2011. A revision of daily egg production estimation methods, with application to Atlanto-Iberian sardine. 1. Daily spawning synchronicity and estimates of egg mortality. – ICES Journal of Marine Science, 68: . Assumptions of daily spawning synchronic...

Bernal, M., Stratoudakis, Y., Wood, S., Ibaibarriaga, L., Uriarte, A., Valdés, L., and Borchers, D. 2011. A revision of daily egg production estimation methods, with application to Atlanto-Iberian sardine. 2. Spatially and environmentally explicit estimates of egg production. – ICES Journal of Marine Science, 68: . A spatially and environmentally e...

Zwolinski, J. P., Oliveira, P. B., Quintino, V., and Stratoudakis, Y. 2010. Sardine potential habitat and environmental forcing off western Portugal. – ICES Journal of Marine Science, 67: 1553–1564. Relationships between sardine (Sardina pilchardus) distribution and the environment off western Portugal were explored using data from seven acoustic s...

Marçalo, A., Marques, T. A., Araújo, J., Pousão-Ferreira, P., Erzini, K., and Stratoudakis, Y. 2010. Fishing simulation experiments for predicting the effects of purse-seine capture on sardine (Sardina pilchardus). – ICES Journal of Marine Science, 67: 334–344. To study the impact of purse-seine fishing on deliberately released sardine, two laborat...

Estimation of fish abundance from acoustic surveys requires the estimation of total acoustic backscatter of the target species in the sampled region. Although the arithmetic mean of acoustic backscatter is an unbiased estimator of the mean backscatter for regular or random sampling designs, under the presence of spatial structure, its use leads to...

Data from 10 acoustic surveys targeting sardine (spring and autumn), 3 acoustic surveys targeting blue whiting (spring) and 9 groundfish surveys (summer and autumn) were used to describe the distribution and relative abundance of snipefish (Macroramphosus spp.) off Portugal and the Gulf of Cadiz in recent years (1998-2003). Snipefish (8-17 cm) were...

Silva, A., Skagen, D. W., Uriarte, A., Massé, J., Santos, M. B., Marques, V., Carrera, P., Beillois, P., Pestana, G., Porteiro, C., and Stratoudakis, Y. 2009. Geographic variability of sardine dynamics in the Iberian Biscay region. – ICES Journal of Marine Science, 66: 495–508. The spatio-temporal variability in the distribution, demographic struct...

The assessment and management of small pelagic fish (SPF) stocks is particularly difficult and uncertain because their short life expectancy, characteristic aggregative behavior, rapid response to climate and environmental signals and large and variable natural mortality make them less tractable through traditional population dynamic models and ass...

We investigated and compared the pattern of accumulation of recent and late atretic follicles in the ovaries of Iberian sardine, Sardina pilchardus, in relation to body size with the aim to examine whether late atresia can be used in back-calculations of individual spawning history. Oppositely to earlier stages, late atresia in sardine was shown to...

Surface velocity estimates from wind and altimeter data, together with satellite-derived sea surface temperature and chlorophyll, were used to explore the advection patterns and environmental conditions using a simple Lagrangian model. Although the model is generic (only considering the physical transport), the results are of particular interest fo...

Presentation of Working Group on Acoustic and Egg Surveys for Sardine and Anchovy in ICES areas VIII and IX

This study describes broad-scale spatial variations in sardine growth across the northeastern Atlantic and Mediterranean waters using opportunistic samples collected in recent years. More detailed information on spatial, decadal and seasonal growth variations is provided for the Iberian-Biscay region using data collected in acoustic surveys since t...

The main factors that affect early survival, physical damage and stress reactions of sardine Sardina pilchardus after live capture and introduction to captivity were examined. A total of 2800 sardines were captured alive from commercial purse seiners in five trials off southern Portugal and monitored for 4 weeks in aquaculture tanks. Survival rates...

Data on the occurrence of sardine (Sardina pilchardus) eggs from 42 national ichthyoplankton surveys along the European Atlantic coast were collated in order to describe the spawning habitat and spawning distribution of sardine in recent decades (1985–2005). A modification of existing spawning habitat characterisation techniques and a newly develop...

Egg data from ichthyoplankton monitoring sites in the western English Channel (1988–2003) and northern Spain (1990–2000) and macroscopic maturity data from biological samples of purse seine landings in western and southern Iberia (1980–2004) are used to describe the spawning seasonality of sardine (Sardina pilchardus) in European waters of the nort...

Zwolinski, J., Morais, A., Marques, V., Stratoudakis, Y., and Fernandes, P. G. 2007. Diel variation in the vertical distribution and schooling behaviour of sardine (Sardina pilchardus) off Portugal. – ICES Journal of Marine Science, 64: 963–972. Diel patterns in the schooling behaviour and vertical distribution of pelagic fish schools were studied...

In the CNS, the monoamine neurotransmitter-neuromodulator serotonin (5-Hydroxytryptamine, 5-HT) is critical for maintaining normal cognitive and emotional processes. With respect to animal welfare, it should particularly be noted that 5-HT is paramount in controlling neurogenesis and synaptic plasticity, processes without which learning ability, me...

Inaccuracy in the aging of postovulatory follicles (POFs) and in estimating the effect of temperature on the resorption rate of POFs may introduce bias in the determination of the daily spawning age classes with the daily egg production method (DEPM). To explore the above two bias problems with field-collected European pilchard (Sardina pilchardus,...

High-resolution acoustic and ichtyoplankton sampling with a 'continuous under-way fish egg sampler (CUFES)' was performed in two regions of approximately 100 square nautical miles off southern Iberian Peninsula, with the aim of studying the small scale distribution of sardine ( Sardina pilchardus) adults and eggs during a spawning event. Very dense...

Spawning temperature preferences for sardine (Sardinapilchardus) in the eastern North Atlantic were determined from egg survey data. These were compared with climatological temperature cycles (198615.0°C from the English Channel to Portugal and 16.0–18.0°C for all north-west African regions. Spawning seasons were closely related to the general lati...

We investigate spatial and temporal variations in sardine maturation patterns and discuss the implications for stock structure, using recent samples collected opportunistically across the species range and data collected regularly for the assessment of the Atlanto-Iberian stock. Maturity ogives were fitted to maturity-at-length data using Generaliz...

More than 120 surveys over 25 years suggest that appropriate use of the daily egg production method (DEPM) provides unbiased but rather imprecise estimates of spawning biomass (coefficient of variation generally above 30%). Knowledge of species reproductive biology and early life history and a survey design adapted to local population dynamics are...

Observations from the purse seine fishery off northern Portugal are used to describe the early dynamics of sardine (Sardina pilchardus) stress reactions and identify likely stressors during the commercial fishing operation. Sardine blood and muscle were sampled from the onset of fishing (school identification and encircling) to the end of fish tran...

Courtship sounds made by three sympatric cichlid species, Pseudotropheus zebra, P. callainos and an undescribed species known as P. ‘zebra gold’ were recorded and compared to investigate the potential role of acoustic signals in mate choice. Sounds were emitted during ‘quiver’ and ‘circle’ components of the male courtship display and consisted of r...

Within the EU project SARDYN, tagging laboratory experiments and operations at sea were designed to study the movements of sardine (Sardina pilchardus) off the Iberian peninsula. In the summer of 2003, around 2500 fish were caught and transferred alive to aquaculture tanks (IEO-Vigo and IPIMAR-Olhão). Mortality ranged between 10-30% in the first we...

ICES CM 2004/Q:19 Sardine (Sardina pilchardus) spawning season in the North East Atlantic and relationships with sea surface tem-perature Yorgos Stratoudakis, Steve Coombs, Tim Smyth, Jerom Costas, Concha Franco, Ana Lago de Lanzós, Alexandra Silva, Maria Begoña Santos, Paula Alvarez, and Maria Santos Sardine (Sardina pilchardus) spawning occurs al...

The acoustic repertoire of captive grey gurnard Eutrigla gurnardus during competitive feeding consisted of three types of sound: knocks, grunts and growls. Knocks were audible as a single sound, whereas grunts and growls were perceived as longer, pulsed sounds to the human ear. Typically, knocks were composed of 1–2 pulses, grunts of 4–8 pulses and...

Lasker (1985) provides the first and most thorough report on the use of the Daily Egg Production Method (DEPM) for the estimation of the spawning biomass of small pelagic fish stocks. An update to this report is provided by Anonymous (1997), a compilation of research papers resulting from an EU concerted action on DEPM techniques. The present Coope...

Surface water samples were collected before, during and after purse seining for sardine off northern Portugal (12 sets) to test the hypothesis that fishing can lead to changes in local nutrient concentrations. Ammonia, urea, residual organic nitrogen and phosphate concentrations significantly increased during fishing and the increase was a pulse ev...

Generalized additive models (GAMs) were fitted to sardine (Sardina pilchardus) egg distribution data from three daily egg production method surveys. The results showed that the area of egg cover off Portugal decreased significantly from 11 800 km2 in 1988 to 7000 km2 in 1997 and 7400 km2 in 1999. This is because of a significant reduction in sardin...

We found 1049 of 2409 mackerel eggs (46%) from 59 samples in the north-east Atlantic to be parasitized by the dinoflagellate Ichthyodinium chabelardi. The endogenous life cycle of the parasite is briefly described.

Observations aboard purse-seiners demonstrated that deliberate lowering of the net to allow pelagic fish to escape ("slipping") was frequent off northern Portugal during the second semester of 2001. Some slipping occurred in 25 of 30 trips observed, and the quantities slipped were significantly higher when the net was set on dense echo-sounder mark...

Atresia in the ovaries of sardine Sardina pilchardus did not show clear seasonal patterns. There was high prevalance (c. 60%) and low intensity (c. 1% of gonadal area occupied by oocytes) in all months of the spawning season studied. The batch size to ovary-free mass relationship was significantly different in the mid-spawning season, with higher r...

Nephrops norvegicus (Norway lobster or prawn) is an important target species in demersal fisheries of the north-east Atlantic. Trawling for Nephrops is wasteful when many small fish are caught and discarded in the process. Here, data from 106 commercial fishing trips, sampled between 1982 and 1998 as part of the Scottish discard sampling programme,...

: In the absence of adequate model-based estimators, estimation of spawning biomass from the Daily Egg Production Method (DEPM) is entirely based on the selected survey design, using design-based estimators. Judgement sampling and survey post-stratification have been recommended as ways of achieving sampling proportional to local fish densities and...