Stochastic Modelling to Assess External Environmental Drivers of Atlantic Chub Mackerel Population Dynamics

The population dynamics of small and middle-sized pelagic fish are subject to considerable interannual and interdecadal fluctuations in response to fishing pressure and natural factors. However, the impact of environmental forcing on these stocks is not well documented. The Moroccan Atlantic coast is characterized by high environmental variability due to the upwelling phenomenon, resulting in a significant abundance and variation in the catches of small and middle-sized pelagic species. Therefore, understanding the evolution of stock abundance and its relationship with different oceanographic conditions is a key issue for fisheries management. However, because of the limited availability of independent-fishery data along the Moroccan Atlantic coast, there is a lack of knowledge about the population dynamics. The main objective of this study is to test the correlation between the environment conditions and the stock fluctuations trends estimated by a stock assessment model that does not need biological information on growth, reproduction, and length or age structure as input. To achieve this objective, the fishery dynamics are analyzed with a stochastic surplus production model able to assimilate data from surveys and landings for a biomass trend estimation. Then, in a second step, the model outputs are correlated with different environmental (physical and biogeochemical) variables in order to assess the influence of different environmental drivers on population dynamics. This two-step procedure is applied for chub mackerel along the Moroccan coast, where all these available datasets have not been used together before. The analysis performed showed that larger biomass estimates are linked with periods of lower salinity, higher chlorophyll, higher net primary production, higher nutrients, and lower subsurface oxygen, i.e., with an enhanced strength of the upwelling. In particular, acute anomalies of these environmental variables are observed in the southern part presumably corresponding to the wintering area of the species in the region. The results indicate that this is a powerful procedure, although with important limitations, to deepen our understanding of the spatiotemporal relationships between the population and the environment in this area. Moreover, once these relationships have been identified, they could be used to generate a mathematical relationship to simulate future population trends in diverse environmental scenarios.Postprin

Nutrient Assessment in the waters of the Oualidia lagoon, Moroccan Atlantic

The Oualidia lagoon is a shallow, nutrient-poor system that suffers from the expansion of oyster farming and agricultural drainage discharges. From an ecological point of view, this lagoon is probably one of the minor conserved wetlands in the Moroccan Atlantic zone. Therefore, the distribution of nutrients (PO43-, NH4+, and NO2-) and physicochemical parameters (temperature, dissolved O2, and salinity) were evaluated for one and a half years. For this purpose, the monitoring of nutrients in the Oualidia lagoon was carried out in four stations. The first results showed a considerable spatial and temporal variability of the physicochemical parameters. Indeed, nutrients of anthropogenic origin have been transported from agricultural areas to the Oualidia basin. However, these inputs were compensated by water exchanges with the adjacent open sea. These exchanges exerted a dynamic dilution effect and induced a short residence time in the water, thus limiting the enrichment and accumulation of nutrients for long periods. An overview of the previous studies, a comparison, and a hydrochemical characterization were performed to evaluate this work's results and give a general picture of the Moroccan Atlantic lagoons (i.e., Moulay Bousselham, Sidi Moussa, Oualidia, and Khnifiss)

Second Workshop on Atlantic chub mackerel (Scomber colias) (WKCOLIAS2)

The Atlantic chub mackerel Scomber colias has become an increasingly important commercial species in the European Atlantic waters in the last 10–15 years, probably through an expansion process from NW African waters and due to market needs. However, at present there are no assessment or advice requirements. In the WK framework, available information of the species in the West Atlantic waters has been compiled in order to evaluate possible geographical differences and trends, and the feasibility to describe its population structure. Though the Atlantic chub mackerel is not routinely included among the target species in the acoustic surveys performed in the Atlantic Iberian waters and the Mediterranean Sea, a synoptic overview of the species is possible over all its West Atlantic distribution. Moreover, the data available have indicated latitudinal trends, mainly in the landings’ length composition, L50 and the spawning periods. Nevertheless, even if some degree of connectivity likely exists and migrations are occurring between adjacent areas, some subunits could be considered for management purposes. From the assessment models’ trials carried out, the results or reference points obtained for the European fisheries cannot be retained at present. Therefore, continuing collating information from fisheries and biological sampling of the species, obtaining reliable biomass estimations from scientific surveys and identifying management units seem the main priorities to address in future research work and in case of assessment requirements

Stochastic Modelling to Assess External Environmental Drivers of Atlantic Chub Mackerel Population Dynamics

The population dynamics of small and middle-sized pelagic fish are subject to considerable interannual and interdecadal fluctuations in response to fishing pressure and natural factors. However, the impact of environmental forcing on these stocks is not well documented. The Moroccan Atlantic coast is characterized by high environmental variability due to the upwelling phenomenon, resulting in a significant abundance and variation in the catches of small and middle-sized pelagic species. Therefore, understanding the evolution of stock abundance and its relationship with different oceanographic conditions is a key issue for fisheries management. However, because of the limited availability of independent-fishery data along the Moroccan Atlantic coast, there is a lack of knowledge about the population dynamics. The main objective of this study is to test the correlation between the environment conditions and the stock fluctuations trends estimated by a stock assessment model that does not need biological information on growth, reproduction, and length or age structure as input. To achieve this objective, the fishery dynamics are analyzed with a stochastic surplus production model able to assimilate data from surveys and landings for a biomass trend estimation. Then, in a second step, the model outputs are correlated with different environmental (physical and biogeochemical) variables in order to assess the influence of different environmental drivers on population dynamics. This two-step procedure is applied for chub mackerel along the Moroccan coast, where all these available datasets have not been used together before. The analysis performed showed that larger biomass estimates are linked with periods of lower salinity, higher chlorophyll, higher net primary production, higher nutrients, and lower subsurface oxygen, i.e., with an enhanced strength of the upwelling. In particular, acute anomalies of these environmental variables are observed in the southern part presumably corresponding to the wintering area of the species in the region. The results indicate that this is a powerful procedure, although with important limitations, to deepen our understanding of the spatiotemporal relationships between the population and the environment in this area. Moreover, once these relationships have been identified, they could be used to generate a mathematical relationship to simulate future population trends in diverse environmental scenarios

An ecopath model for fisheries management in the Mogador marine protected area (Moroccan, Atlantic)

The high exploitation of marine fisheries resources for their economic value along with climate change in recent decades is threatening the regeneration of these resources. Available data on the state of fish stocks and the trophic organization and functioning of these aquatic environments are currently in insufficient. Considering this situation, we aim in this study to improve the knowledge and information available on the functioning of Mogador marine protected area (MPA), one of the marine ecosystems in the Moroccan Atlantic coasts which was established to support the conservation of the local fisher- ies. An Ecopath model is applied for this Mogador MPA which is represented by 27 functional groups including 18 fishes, which are grouped based on many criteria mainly their size and commercial importance in the fisheries of the study region. A series of indicator for the food web are identified through model statistics and web analysis. The results obtained show relatively high ecotrophic efficiency with a transfer efficiency close to10%, indicating a good degree of stability. Analysis of mixed trophic impact shows significant top-down control of the food web in this system. This study highlights the potential benefits of using an ecotrophic model to assess the effects of fishing on stocks

Linking oceanographic products to fisheries advice

This report focuses on encouraging usage of Copernicus Marine Service products by fisheries users and scientists, and consists of a number of key studies where numerous EuroSea activities support the uptakes of Copernicus Marine Service data products, focusing on Atlantic mackerel, European hake and Atlantic tuna. The report also contains an intercomparison study focused on oceanographic equipment (CTD) to determine the most suitable sensor for a fisheries observing system. A number of recommendations are provided on how to support the use of Copernicus Marine Service products in fisheries science, such as the production of new Best Practices, stronger partnerships (fisheries scientists and oceanographers) and co-development of ocean indicators

Bibliometric research analysis on the Oualidia and Sidi Moussa lagoons, Moroccan Atlantic coast

This investigation presents the evolution of scientific production, based upon a bibliometric study from 1974 to May 2021, including aspects such as the progress, trends, and hotspots of coastal research in Oualidia and Sidi Moussa lagoons (Moroccan Atlantic coast). In addition, the research investigation includes publication year, document type, language, and mainstream journals. Co-words, co-country and co-authorship analysis were conducted using VOSviewer software. A total of 351 publications were extracted. Of these publications, 276 (78.63%) were academic papers. The study revealed a disparity in the research distribution: 62.11% of the total publications were referred to Oualidia lagoon and only 37.89% to Sidi Moussa lagoon. 57.26% of them were produced between 2011 and 2021. Morocco, France, and Spain are the most important countries for international cooperation in this research area. Studies did exhibit heterogeneity regarding research priorities. Some prioritized environmental monitoring and water quality issues, while others focused more on topics such as heavy metal pollution. In contrast, the application of new monitoring methods for lagoons investigation, new technologies, processes, and models of ecological restoration received little attention