Search

Aim: Previous analyses of marine fish species richness based on presence-absence data have shown changes with latitude and average species size, but little is known about the underlying processes. To elucidate these processes we use metabolic, neutral and descriptive statistical models to analyse how richness responds to maximum species length, fish abundance, temperature, primary production, depth, latitude and longitude, while accounting for differences in species catchability, sampling effort and mesh size. Data: Results from 53,382 bottom trawl hauls representing 50 fish assemblages. Location: The northern Atlantic from Nova Scotia to Guinea. Time period: 1977–2013. Methods: A descriptive generalized additive model was used to identify functional relationships between species richness and potential drivers, after which nonlinear estimation techniques were used to parameterize: (a) a ‘best’ fitting model of species richness built on the functional relationships, (b) an environmental model based on latitude, longitude and depth, and mechanistic models based on (c) metabolic and (d) neutral theory. Results: In the ‘best’ model the number of species observed is a lognormal function of maximum species length. It increases significantly with temperature, primary production, sampling effort, and abundance, and declines with depth and, for small species, with the mesh size in the trawl. The ‘best’ model explains close to 90% of the deviance and the neutral, metabolic and environmental models 89%. In all four models, maximum species length and either temperature or latitude account for more than half of the deviance explained. Main conclusions: The two mechanistic models explain the patterns in demersal fish species richness in the northern Atlantic almost equally well. A better understanding of the underlying drivers is likely to require development of dynamic mechanistic models of richness and size evolution, fit not only to extant distributions, but also to historical

The ICES Working Group on Ecosystem Assessment of Western European Shelf Seas (WGEAWESS) meeting was held in Lisbon (Portugal), on 24–28 April 2017. The meeting was attended by 8 participants from 4 countries and chaired by Steven Beggs, Northern Ireland (UK). This was the first year of the new 3-year Terms of Reference (ToR) for WGEAWESS. The main activities for the group at the 2017 meeting were to discuss progress and further development of work towards the ToRs a) Continue metadata compilation for all ecosystem components available for IEA development, b) Continue evaluation of data and trends for a regional Integrated Ecosystem Assessment (IEA). Identify ecosystem trends relevant to stock assessment and management. As an outcome of specific objectives to integrate the activities of WGEAWESS with sister IEA groups, the meeting was held back to back with both the ICES/HELCOM Working Group on Integrated Assessments of the Baltic Sea (WGIAB) and the Working Group on Comparative Analyses between European Atlantic and Mediterranean marine ecosystems to move towards an Ecosystem-based Approach to Fisheries (WGCOMEDA). This back to back meeting had many advantages and provided much opportunity for group integration and future collaboration.

Providing regional integrated ecosystem assessments (IEA) is a key challenge identified in the ICES Strategic Plan (2014-2018). IEAs are seen as a fundamental link between advice and ecosystem science inachieving Ecosystem Based Management (EBM).While EBM is not a new concept, difficulties in achieving such an ambitious goal have been highlighted by the extensive work conducted in this area. The implementation of new regulation policies, such as the Marine Strategy Framework Directive (MSFD) and the reformed Common Fisheries Policy (CFP) in Europe,have challenged the scientific community to rapidly react despite these difficulties and provide scientific advice to support management decisions concerning these policies. RegionalICES groups have been tasked with developing methods and tools for IEA in their corresponding ecoregions; this is the case of the Working Group on Ecosystem Assessment of Western European Shelf Seas (WGEAWESS). The role of this group is to implement, and test tools and methods for the advisory process, focusing on the North Atlantic European continental shelf, including Celtic Seas, Bay of Biscay and Iberian Waters. In this presentation we show the progress made within this WG during its initial three years of activity, in relation to some of the terms of reference already addressed. An adaptation of the ODEMM framework has been selected as a tool for identifying a) links between components, processes, pressures and states, and b) gaps in data availability and indicator implementation. Some preliminary results of a first IEA exercise will also been shownwith emphasis onthe MSFD descriptors D1 (biological diversity) and D4 (food webs).

The dynamics of Sardina pilchardus in Iberian upwelling are examined. Spawning-stock biomass (SSB), recruitment (R), and production (R/SSB) data for the years 1978-2006 are analysed in relation to the upwelling index (UPW) and sea surface temperature (SST). The population oscillates in two relatively stable orbits (identified by multiresolution decomposition of the recruitment series) because the external forcing (UPW and SST) are the inverse of each other and the synchrony is lost between the two external variables, R and R/SSB as they shift towards steep, negative (depensatory) trends. Such mechanics may have induced recruitment failures and significant decreases in abundance of Iberian sardine. The relationships are assumed to validate a complex and dynamic continuum (multiple orbits of stability) and an alternative variable-carrying- capacity population model. Radial systems with two orbits of stability are proposed for the R/SSB and S/SSB (where S is the stock size) relationships. Results are discussed in relation to classical and alternative SR models to address stock rehabilitation and fishing mortality issues as the population shifts towards low recruitment and abundance, and critical factors to consider in developing exploitation strategies for systems with multiple orbits of stability are discussed

Background is provided to the selection of ecological indicators by the IndiSeas Working Group, and the methodology adopted for analysis and comparison of indicators across exploited marine ecosystems is documented. The selected indicators are presented, how they are calculated is explained, and the philosophy behind the comparative approach is given. The combination of selected indicators is intended to reflect different dynamics, tracking processes that display differential responses to fishing, and is meant to provide a complementary means of assessing marine ecosystem trends and states. IndiSeas relied on inputs and insights provided by the local experts from participating ecosystems, helping to understand state and trend indicators and to disentangle the effect of other potential ecosystem drivers, such as climate variability. This project showed that the use of simple and available indicators under an ecosystem approach can achieve a real, wide-reaching evaluation of marine ecosystem status caused by fishing. This is important because the socio-economics of areas where fishing activities develop differs significantly around the globe, and in many countries, insufficient data are available for complex and exhaustive analyses

The usefulness of indicators in detecting ecosystem change depends on three main criteria: the availability of data to estimate the indicator (measurability), the ability to detect change in an ecosystem (sensitivity), and the ability to link the said change in an indicator as a response to a known intervention or pressure (specificity). Here, we specifically examine the third aspect of indicator change, with an emphasis on multiple methods to explore the "relativity" of major ecosystem drivers. We use a suite of multivariate methods to explore the relationships between a pre-established set of fisheries-orientated ecosystem status indicators and the key drivers for those ecosystems (particularly emphasizing proxy indicators for fishing and the environment). The results show the relative importance among fishing and environmental factors, which differed notably across the major types of ecosystems. Yet, they also demonstrated common patterns in which most ecosystems, and indicators of ecosystem dynamics are largely driven by fisheries (landings) or human (human development index) factors, and secondarily by environmental drivers (e.g. AMO, PDO, SST). How one might utilize this empirical evidence in future efforts for ecosystem approaches to fisheries is discussed, highlighting the need to manage fisheries in the context of environmental and other human (e.g. economic) drivers

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 sardine egg presence off northern Portugal, GAM estimated areas being similar or higher in the late 1990s for southwestern and southern Portugal. The distributional area covered by larvae was not estimated for 1988 (larval distribution extended beyond the survey area), although it was probably higher than the 9600 km2 for 1997 and 5500 km2 for 1999. In 1997 and 1999, the Gulf of Cadiz was also sampled, indicating extensive areas with sardine eggs and larvae (more than 50% of the total area of distribution off Portugal). Standardized data from 15 ichthyoplankton surveys between 1985 and 2000 show a decline in the mean probability of egg presence within the Portuguese continental shelf from the mid-1980s to the late-1990s, because of a marked reduction in egg presence off northern Portugal. Sardine larval data from the same surveys suggest that the reduction in mean probability of presence in the north is less marked than for eggs (although this comparison ignores the presence of sardine larvae beyond the continental shelf in the 1980s). Similar changes off northern Portugal and western Galicia are observed in commercial sardine catches and the acoustically estimated area of fish distribution. It is possible that the observed decline in spawning area off northwestern Iberia during the 1990s is indirectly reflecting the prevalence of environmental conditions detrimental to sardine recruitment (northerly winds during winter that favour coastal upwelling and offshore transport), which have reduced the spawning contribution of young fish in that area.

Spanish Oceanogrnphic Institute (IEO) and Portuguese Research Inistitute (IPIMAR, ex-INIP) using their research vessels "Comide de Saavedra" and "Noruega" have conducted groundfish surveys in Spanish and Portuguese waters. The results of these surveys have been reported to the relevant ICES Working Groups, communicated to ICES Annual Conferences and/or published in journals of bioiogy and flsheries. Data collected from groundfish surveys were also the basis to carry out assemblage studies and to several advices to the Spanish, Porttuguese and European fishery administrations concerning the implementation of technical measures for fish stock management. This communication intends to give information about the past, the present and the future of these surveys, concerning objectives, methodology and publications. Critical aspects and solutions to improve some aspects are presented.