Density dependence in the spatial behaviour of anchovy and sardine across Mediterranean systems

A spatial indicator—the spreading area index—is used to describe anchovy and sardine spatial distribution in relation to biomass variation and to look for ecosystem differences within the Mediterranean basin. Specifically, the variation in the spreading area index in relation to biomass was examined for different areas of the Mediterranean Sea (i.e. Aegean Sea, western Adriatic Sea, Strait of Sicily, Gulf of Lion, and Spanish Mediterranean waters). In order to capture the spatial variability of the population at different levels of fish density, acoustic survey data for the years of highest, lowest, and intermediate abundance were used. In a subsequent step standardized values of spreading area and biomass were estimated to allow comparisons. Results showed pronounced area differences. A significant relationship was revealed in the case of anchovy for areas with extended continental shelf (i.e. Aegean Sea, Adriatic Sea, and Gulf of Lion), indicating an increase in biomass with an increase in the spreading area. No relationship was found for areas dominated by narrow continental shelf and strong currents (i.e. Spanish Mediterranean waters and the Strait of Sicily). With regard to sardine, an increase in biomass was followed by an increase in the spreading area when estimates from the Aegean Sea, the Adriatic Sea, and the Strait of Sicily were considered together. The relationship was even more Abstracts–Theme Session B 9 pronounced when analysis was limited to the Aegean Sea and the Strait of Sicily. No relationship was found for the Spanish Mediterranean waters and the Gulf of Lion. This clearly implies that spatial indicators should be integrated into ecosystem management, taking into account that they can be area‐ or ecosystem‐dependent

The Seascape of Demersal Fish Nursery Areas in the North Mediterranean Sea, a First Step Towards the Implementation of Spatial Planning for Trawl Fisheries

The identification of nursery grounds and other essential fish habitats of exploited stocks is a key requirement for the development of spatial conservation planning aimed at reducing the adverse impact of fishing on the exploited populations and ecosystems. The reduction in juvenile mortality is particularly relevant in the Mediterranean and is considered as one of the main prerequisites for the future sustainability of trawl fisheries. The distribution of nursery areas of 11 important commercial species of demersal fish and shellfish was analysed in the European Union Mediterranean waters using time series of bottom trawl survey data with the aim of identifying the most persistent recruitment areas. A high interspecific spatial overlap between nursery areas was mainly found along the shelf break of many different sectors of the Northern Mediterranean indicating a high potential for the implementation of conservation measures. Overlap of the nursery grounds with existing spatial fisheries management measures and trawl fisheries restricted areas was also investigated. Spatial analyses revealed considerable variation depending on species and associated habitat/depth preferences with increased protection seen in coastal nurseries and minimal protection seen for deeper nurseries (e.g. Parapenaeus longirostris 6%). This is partly attributed to existing environmental policy instruments (e.g. Habitats Directive and Mediterranean Regulation EC 1967/2006) aiming at minimising impacts on coastal priority habitats such as seagrass, coralligenous and maerl beds. The new knowledge on the distribution and persistence of demersal nurseries provided in this study can support the application of spatial conservation measures, such as the designation of no-take Marine Protected Areas in EU Mediterranean waters and their inclusion in a conservation network. The establishment of no-take zones will be consistent with the objectives of the Common Fisheries Policy applying the ecosystem approach to fisheries management and with the requirements of the Marine Strategy Framework Directive to maintain or achieve seafloor integrity and good environmental status.Versión del editor4,411

Uncertainty in stock assessments, spatial distribution and habitat modelling of two small pelagic fish species, sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus), in the Mediterranean from late autumn spanish acoustic surveys

[cat] Els petits peixos pelàgics són espècies de peixos que viuen a la columna d’aigua i que tenen poca relació amb el fons marí. Durant el dia formen bancs de peixos amb l’objectiu alimentar-se, defensar-se en front potencial depredadors o per eficiència energètica, dispersant-se durant la nit. La importància dels petits pelàgics a l’ecosistema marí radica en la proporció de biomassa que representen i en la funció clau que exerceixen com esglaons intermedis, transferint energia entre les nivells inferiors i superiors de la cadena tròfica. Les seves poblacions són particularment sensibles a les fluctuacions ambientals (Cole and McGlade, 1998; Lloret et al., 2004) i freqüentment es troben baix un règim d’explotació elevat per part de les pesqueres comercials. Això pot comportar de manera ocasional el col·lapse de les seves poblacions explotables, afectant a l’ecosistema marí i a les pesqueries que sostenen. Gairebé el 50% del total de la biomassa anual desembarcada als ports del Mediterrani prové dels petits peixos pelàgics (Lleonart and Maynou, 2003). Al Mediterrani Occidental, la sardina (Sardina pilchardus) i l’aladroc (Engraulis encrasicolus) són les dues espècies més importants, tant en termes de biomassa capturada com pel seu interès comercial (Lleonart and Maynou, 2003). Malgrat la seva importància, la distribució espaial de les poblacions explotables és poca coneguda així com també ho és la relació d’aquesta distribució espaial amb variables ambientals. D’ençà de principis dels anys 90, es duen a terme campanyes acústiques a la plataforma continental del Mediterrani espanyol a finals de la tardor (Abad et al., 1998 a,b), coincidint amb el reclutament de l’aladroc i amb l’època de posta de la sardina (Abad and Giráldez, 1993; Giráldez and Abad, 1995). Tot i que el principal objectiu d’aquestes campanyes és l’estimació de l’abundància i de la biomassa de la sardina i l’aladroc, dades del conjunt de la comunitat pelágica també es recolleixen. A més a més, al llarg de la darrera dècada s’ha detectat una aparició incremental d’altres espècies de petits i mitjans pelàgics i per tant, es va aconsellar l’aplicació d’un enfoc multiespecífic a l’avaluació de les pesqueres del Mediterrani (Lleonart and Maynou, 2003). El present treball s’estructura en dues seccions principals. La primera secció del treball analitzarà la distribució espaial (1D i 2D) de la sardina i l’aladroc per mitjà de tècniques geoestadístiques, tant transitives com intrínseques (Matheron, 1969). Es prestarà especial atenció a la incerteza associada a les estimacions d’abundància i, concretament, a la incertesa originada pel disseny de mostreig que és considerat un dels factors que contribueixen amb més intensitat a l’error aleatori (ICES, 1998). La segona secció explorarà els factors ambientals que condicionen la presència o absència de sardina i aladroc a finals de tardor. Dades ambientals obtingudes de satèl·lit, com la temperatura superficial de la mar, la salinitat, clorofil·la, radiació fotosintèticament activa, anomalies del nivell de la mar i la profunditat del fons marí es relacionaran amb la presència-absència de les poblacions explotables de sardina i aladroc mitjançant models additius generalitzats (GAM, de l’acrònim anglès) per determinar les relacions existents (Bellido et al., 2008; Giannoulaki et al., 2008). L’hàbitat de la posta de la sardina serà igualment estudiada per tal de modelar la presència-absència d’ous de sardina i intentar entendre l’evolució de les seves poblacions explotables.[spa] Los pequeños peces pelágicos son especies que viven en la columna de agua y que tienen poca relación con el fondo marino. Durante el día forman bancos de peces con el objetivo de alimentarse, defenderse de potenciales depredadores o por motivos de eficiencia energética, dispersándose durante la noche. La importancia de los pequeños pelágicos en el ecosistema marino radica en la proporción de biomasa que representan y en la función clave que desempeñan como eslabones intermedios, transfiriendo energía entre los niveles tróficos inferiores y superiores de la cadena trófica. Sus poblaciones son particularmente sensibles a las fluctuaciones ambientales (Cole and McGlade, 1998; Lloret et al., 2004) y frecuentemente se encuentran en un régimen de explotación elevado por parte de las pesquerías comerciales. Esto puede comportar de manera ocasional el colapso de sus poblaciones explotables, afectando al ecosistema marino y a las pesquerías que las mantinen. Casi el 50% del total de la biomssa anual desembarcada en los puertos del Mediterráneo provienen de los pequeños peces pelágicos (Lleonart and Maynou, 2003). En el Mediterráneo Occidental, la sardina (Sardina pilchardus) y el boquerón (Engraulis encrasicolus) son las dos especies más importantes, tanto en términos de biomasa como capturada como por su interés comercial (Lleonart and Maynou, 2003). A pesar de su importancia, la distribución espacial de las poblaciones explotables es poco conocida así como también lo es la relación de la distribución espacial con los parámetros ambientales. Desde principios de los años 90, se llevan a cabo campañas acústica en la plataforma continental española del Mediterráneo a finales de otoño (Abad et al., 1998 a,b), coincidiendo con el reclutamiento de la anchoa y la época de puesta de la sardina (Abad and Giráldez, 1993; Giráldez and Abad, 1995). A pesar de que el principal objetivo de estas campañas es la estimación de la abundancia y de la biomas de la sardina y el boquerón, datos de la comunidad pelágica en conjunto también se recogen periódicamente. Además, a lo largo de la última década se ha detectado una aparición incremental de otras especies de pequeños y medianos pelágicos y por tanto, se aconsejó la aplicación de un enfoque multiespecífo en la evaluación de pesquerías del Mediterráneo (Lleonart and Maynou, 2003). El presente trabajo se estructura en dos seciones. La primera sección del trabajo analizará la distribución espacial (1D y 2D) de la sardina y el boquerón por medio de técnicas geoestadísticas, tanto transitivas como intrínsecas (Matheron, 1969). Se prestará especial atención a la incertidumbre asociasda a las estimaciones de abundancia y, concretamente, a la incertidumbre asociada al diseño de muestro que se considera uno de los factores que contribuyen con mayor intensidad al error aleatorio (ICES, 1998). La segunda sección explorará los factores ambientales que condicioinan la presencia o ausencia de sardina y boquerón a finales de otoño. Datos ambientales obtenidos de satélite, como la temperatura superficial del mar, la salinidad, clorofila, radiación fotosintéticamente activa, anomalía del nivel del mar y la profundidad del fondo marino se relacionarán con la presencia-ausencia de las poblaciones explotables de sardina y boquerón mediante modelos aditivos generalizados (GAM, del acrónimo inglés) para determinar las relaciones existentes (Bellido et al., 2008; Giannoulaki et al., 2008). El hábitat de la puesta de sardina será igualmente estudiada para modelar la presencia-ausencia de huevos de sardina e intentar entender la evolución de las especies explotables.[eng] Small pelagic fish are species that live in the water column and have little relationship with the sea bottom. During the day they may form schools with feeding, defence or energetic efficiency purposes and disperse during the night. The importance of small pelagic fishes within the marine ecosystem rely in the proportion of biomass they represent and the clue function they develop as intermediate links in the energy transfer between lower and upper levels of the trophic chain. Their populations are particularly sensitive to environmental fluctuations (Cole and McGlade, 1998; Lloret et al., 2004) and frequently highly exploited by commercial fisheries. These may occasionally collapse the stocks affecting both the marine ecosystem and the fisheries they sustain. In the Mediterranean, almost 50% of the total annual landings are attributable to small pelagic fishes (Lleonart and Maynou, 2003). In the Western Mediterranean Sea, sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) are the two most important species in terms of landed biomass and commercial interest (Lleonart and Maynou, 2003). Despite their importance little is known about the spatial distribution of these stocks or about the relationship between the spatial distribution and environmental variables. Since the ‘90s acoustic surveys are annually performed in the Spanish Mediterranean continental shelf in late autumn (Abad et al., 1998 a,b) coinciding with anchovy’s recruitment and the beginning of the spawning season for sardine (Abad and Giráldez, 1993; Giráldez and Abad, 1995). Although the main goal of these surveys is to estimate abundance and biomass of sardine and anchovy, data about the whole pelagic community has also been gathered. Furthermore, in the last decade it was detected an increasing appearance of other small and medium-sized pelagic species and the application of a multi-species approach to Mediterranean fisheries assessment was advised (Lleonart and Maynou, 2003). The present work is structured in two sections. The first section of the work will analyse the spatial distribution (1D and 2D) of sardine and anchovy by means of geostatistical techniques, both transitive and intrinsic methods (Matheron, 1969). Special attention will be paid to the estimation of the uncertainty associated to abundance estimations and, concretely, the uncertainty caused by sampling scheme which is thought to be one of the main contributors to random error (ICES, 1998). The second section will explore the environmental factors that drive the presence or absence of anchovy and sardine in late autumn. Satellite environmental data as sea surface temperature, salinity, chlorophyll-a, photosintethic active radiation, sea level anomalies or bottom depth will be related to the presence-absence of sardine and anchovy stocks through Generalised Additive Models (GAM) to try to depict the relationships that may be found between both (Bellido et al., 2008; Giannoulaki et al., 2008). The spawning area of sardine will also be studied in order to model the presence-absence of sardine eggs and try to understand the evolution of their stocks

The recreational fishery off Majorca Island (western Mediterranean): Some implications for coastal resource management

The sociology and habits of recreational anglers on the Island of Majorca (western Mediterranean) were evaluated using telephone and on-site surveys, as well as fishing logbooks and recreational fishing competitions. The recreational fishery is one of the island's main leisure activities, 5.14% of the population (37 265 people) participating. Enthusiasts tend to be mainly middle class (most anglers own boats moored at marinas), middle-aged males (90% male, mean age 46 ± 2 years). The most popular fishing method is from a boat (62.9%), followed by fishing from shore (32.4%), and spearfishing (3.6%). The mean time spent fishing is 3.86 ± 0.03 h d-1, and more than one type of gear (mean 1.27 ± 0.21) is used simultaneously by a single angler. The frequency of fishing is 4-6 times per month, mainly on holidays and weekends, increasing in summer. The activity has a sizeable impact on the coastal fauna, with diverse catches of at least 1209.25 t year-1 (about 615 000 fishing outings year-1). Thus, the amount of carbon extracted annually is at least 137.34 kg C km-2 year-1, and the recreational fishery removes about 31% of production at trophic level 4. Although these are gross estimates and more detailed study of the effect on trophic level and local production is needed, the values do highlight the pressure the recreational fishery exerts on coastal fish communities. Assuming that this level of exploitation is common to north-shore Mediterranean countries, there may be cause for concern about sustainable exploitation in the recreational fishery, and the effectiveness of current protection measures is discussed. Despite the limitations of the study, recreational fisheries clearly should be taken into account when considering measures for fisheries management. Moreover, fishing has considerable social import, and the benefits must be taken into account when investments to protect exploited resources are being contemplated. © 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.Peer Reviewe

Trawl fishery restricted areas in the Mediterranean Sea.

<p>Trawl fishery restricted areas are shown in blue, trawlable areas are shown in white.</p