Fisheries are among the human activities that are most strongly affected by ongoing climate-related changes in the presence and abundance of fish species across the globe. The ecological and social repercussions of such changes for recreational fisheries are however still poorly understood. Here, we explore selected ecological and social dimensions of recreational angling and spearfishing targeting the bluefish (Pomatomus saltatrix) in Italy. The bluefish has undergone a northward expansion in the region over the last 20-30 years, during which it reached new areas and increased in abundance. Using digital videos and their associated data published by recreational fishers on YouTube we characterized ecological and social dimensions using a culturomics approach. Specifically, we focused on harvesting patterns, social engagement and sentiments related to the bluefish. Our study revealed four major results: (i) similar harvesting patterns (i.e., declared mass and seasonal upload patterns) related to videos by recreational anglers and spearfishers; (ii) higher social engagement (i.e., number of views and likes) for videos by recreational anglers than spearfishers; (iii) differences in themes of discussion, with anglers being mainly interested in fishing strategy and gears and spearfishers being more interested in fishing actions shown on the videos; iv) positive and negative sentiments of both recreational anglers and spearfishers towards the invasiveness and aggressiveness of the species. The latter represents an interesting trade-off associated with recreational fishing of the bluefish: it is perceived as an invasive species, but it is also a valued fish target because its voracity contributes to the quality of the recreational fishing experience. Our study showcases the value of exploring social media and associated data to better understand the ecological and human dimensions of marine recreational fisheries in relation to distributional range shifts of species associated with climate change.

Climate change affects the shift range distribution of species, especially among mobile species, and this phenomenon can alter ecosystems and impacts human activities. Fishing is an anthropic activity that undergoes the effect not only of the introduction and increase of non-native species but also of native thermophilic ones. Some of these species can become a commercially exploitable resource. However, this information is often obscured by the negative effects these species can cause to the environment. We investigated how the thermophilic species Caranx rhonchus, neglected in Italy, could become a relevant resource. We studied the nutritional profile and the presence of heavy metal contamination and compared these traits with those of a similar common Mediterranean species, namely Trachurus trachurus. The proximate composition was determined following the AOAC procedure, while the fatty acid profile was determined by GC/MS, and the mineral component was obtained by mass spectrometer (ICP-MS). Caranx rhonchus is a nutritionally good species, although it is little consumed and exploited. Increasing the market supply with new commercially exploitable emerging species would benefit local communities and the environment. Therefore, it is necessary to investigate how a shift of the range caused by climate change can provide benefits within the human dimension.

We applied data mining on YouTube videos to better understand recreational fisheries targeting common dentex (Dentex dentex), an iconic species of Mediterranean fisheries. In Italy alone, from 2010 to 2016 spearfishers posted 1051 videos compared to 692 videos posted by anglers. The upload pattern of spearfishing videos followed a seasonal pattern with peaks in July, a trend not found for anglers. The average mass of the fish declared in angling videos (6.4 kg) was significantly larger than the one in spearfishing videos (4.5 kg). Videos posted by spearfishers received significantly more likes and comments than those posted by anglers. Content analysis suggested that the differences in engagement can be related to appreciation of successful spearfishers necessitating relevant personal qualities for catching D. dentex. We also found that the mass of the fish positively predicted social engagement as well as the degree of positive evaluation only in spearfishing videos. This could be caused by the generally smaller odds of catching large D. dentex by spearfishing. Our case study demonstrates that data mining on YouTube can be a powerful tool to provide complementary data on controversial and data-poor aspects of recreational fisheries and contribute to understanding the social dimensions of recreational fishers.

iEcology and conservation culturomics are two emerging research approaches that rely on digital data for studying ecological patterns and human-nature interactions. We applied data mining of videos published on YouTube related to recreational fishing of four species of groupers (family: Epinephelidae) in Italy between 2011 and 2017 to learn whether digital user-supplied data help uncover key spatio-temporal ecological patterns characteristic of the studied species. Our results support an ontogenetic deepening of the dusky grouper (Epinephelus marginatus) as revealed by a positive relationship between body mass and depth of captures declared in spearfishing videos. In addition, the data support a northward expansion of the white grouper (Epinephelus aeneus) because the average latitude associated to the catch was found to be positively correlated with the years when the videos were uploaded on YouTube. Furthermore, the georeferenced data about the white grouper filled a knowledge gap in a well-established international occurrence records dataset. The approach presented here could help mitigating data deficiencies and inform about harvesting patterns shown by recreational anglers and spearfishers. Our work illustrates the value of digital data associated with recreational fishing for advancing fish and fisheries research. The approach can be broadened to larger spatial and temporal scales, and to different species, contributing to a better understanding of macroecological patterns, assessment and conservation of exploited species, and monitoring of recreational fisheries.

Italy, at the center of the Mediterranean Sea, hosts a high diversity of fishes, but to a certain extent, this richness remains hidden or poorly known because of rare, cryptic or recently introduced species, that are hardly to detect with the traditional sampling approaches. In this study, we gained complementary knowledge, engaging Italian sea users, especially fishers and underwater photographers, to share their observations. Results obtained during 2019 provided 124 new records distributed in 40 species. Most of these records are related to native-rare and native-thermophilic fishes (-95%), while few observations (-5%) concern non-indigenous taxa. Records of thermophilic species were reported from the Tyrrhenian Sea and the Ionian Sea, while alien species were mostly reported from the southernmost coasts of Italy. Our findings highlight the potential of participatory actions and emphasize the value of a close collaboration between researchers and sea-lovers for monitoring marine biodiversity on large spatial scales.

Results of the AlienFish project – monitoring and study of rare and non-indigenous fish species in Italian waters – collected through citizen science in 2018 are here reported. Overall, 36 observations of 21 fish species belonging to 17 families were provided from the central and southern sectors of Italian seas. Our findings highlight the effectiveness of involving sea users in the detection of fish species of both indigenous and non-indigenous origin. Professional fishermen were particularly effective in providing information on rare deep-water and open-water fishes.

The dataset was collected with the the Mediterranean LEK initiative. The initiative was initially conceived by the international basin-wide monitoring program CIESM Tropical Signals (funded by the Albert II of Monaco Foundation) and subsequently adopted by the projects BALMAS (Ballast Water Management System for Adriatic Sea Protection, IPA Adriatic Cross-Border Cooperation Programme; FAO-AdriaMed and FAO-MedSudMed. This action was recently supported by the Interreg Med Programme (Grant number Pr MPA-Adapt 1MED15_3.2_M2_337) 85% co-funded by the European Regional Development Fund, which implemented the use of standard LEK protocols for Marine Protected areas and partially supported the writing of this publication. Data refers to self-reported trends of various fish species, which were regarded as increaseing by a sample of fishermen from various Mediterranean countries. Interviews were elicited from fishermen through semi-structured protocols (see Azzurro et al., 2011).

The seasonal timing of recurring biological processes is essential for organisms living in temperate regions. While ample knowledge of these processes exists for terrestrial environments, seasonal timing in the marine environment is relatively understudied. Here, we characterized the annual rhythm of habitat use in six fish species belonging to the Sparidae family, highlighting the main environmental variables that correlate to such rhythms. The study was conducted at a coastal artificial reef through a cabled observatory system, which allowed gathering underwater time-lapse images every 30 minutes consecutively over 3 years. Rhythms of fish counts had a significant annual periodicity in four out of the six studied species. Species-specific temporal patterns were found, demonstrating a clear annual temporal niche partitioning within the studied family. Temperature was the most important environmental variable correlated with fish counts in the proximity of the artificial reef, while daily photoperiod and salinity were not important. In a scenario of human-induced rapid environmental change, tracking phenological shifts may provide key indications about the effects of climate change at both species and ecosystem level. Our study reinforces the efficacy of underwater cabled video-observatories as a reliable tool for long-term monitoring of phenological events.

Data about recreational fisheries are scarce in many areas of the world. In the absence of monitoring data collected in situ, alternative data sources, such as digital applications and social media platforms, have the potential to produce valuable insights. Yet, the potential of social media for drawing insights about recreational fisheries is still underexplored. In this study, we applied data mining on YouTube videos to better understand recreational fisheries targeting common dentex (Dentex dentex), an iconic species of Mediterranean recreational fisheries. We chose this model species because of ongoing controversies about the relative impact of recreational angling and recreational spearfishing on its conservation status. In Italy alone, from 2010 to 2016 recreational spearfishers posted 1051 videos compared to 692 videos posted by recreational anglers. Only the upload pattern of spearfishing videos followed a seasonal pattern with peaks in July, suggesting seasonality of spearfishing catches of D. dentex – a trend not found for anglers. The average mass of the fish declared in recreational angling videos (6.43 kg) was significantly larger than the one in spearfishing videos (4.50 kg). Videos posted by recreational spearfishers received significantly more likes and comments than those posted by recreational anglers, suggesting that the social engagement among recreational spearfishers was stronger than in anglers. We also found that the mass of the fish positively predicted social engagement in recreational spearfishing videos, but not in videos posted by recreational anglers. This could be caused by the generally smaller odds of catching large D. dentex by spearfishing, possibly explaining why posting videos with particularly large specimen triggered larger social engagement by recreational spearfishers. Our case study demonstrates that data mining on YouTube can be a powerful tool to provide complementary data on controversial and data-poor aspects of recreational fisheries.

Climate change and biological invasions are rapidly reshuffling species distribution, restructuring the biological communities of many ecosystems worldwide. Tracking these transformations in the marine environment is crucial, but our understanding of climate change effects and invasive species dynamics is often hampered by the practical challenge of surveying large geographical areas. Here, we focus on the Mediterranean Sea, a hot spot for climate change and biological invasions to investigate recent spatiotemporal changes in fish abundances and distribution. To this end, we accessed the local ecological knowledge (LEK) of small-scale and recreational fishers, reconstructing the dynamics of fish perceived as "new" or increasing in different fishing areas. Over 500 fishers across 95 locations and nine different countries were interviewed, and semiquantitative information on yearly changes in species abundance was collected. Overall, 75 species were mentioned by the respondents, mostly warm-adapted species of both native and exotic origin. Respondents belonging to the same biogeographic sectors described coherent spatial and temporal patterns, and gradients along latitudinal and longitudinal axes were revealed. This information provides a more complete understanding of the shifting distribution of Mediterranean fishes and it also demonstrates that adequately structured LEK methodology might be applied successfully beyond the local scale, across national borders and jurisdictions. Acknowledging this potential through macroregional coordination could pave the way for future large-scale aggregations of individual observations, increasing our potential for integrated monitoring and conservation planning at the regional or even global level. This might help local communities to better understand, manage, and adapt to the ongoing biotic transformations driven by climate change and biological invaders.

A major problem worldwide is the rapid change in species abundance and distribution, which is rapidly restructuring the biological communities of many ecosystems under changing climates. Tracking these transformations in the marine environment is crucial but our understanding is often hampered by the absence of historical data and by the practical challenge of survey large geographical areas. Here we focus on the Mediterranean Sea, a region which is warming faster than the rest of the global ocean, tracing back the spatio-temporal dynamic of species, which are emerging the most in terms of increasing abundances and expanding distributions. To this aim, we accessed the Local Ecological Knowledge (LEK) of small-scale and recreational fishers reconstructing the dynamics of fish perceived as ‘new’ or increasing in different fishing area. Over 500 fishers across 95 locations and 9 different countries were interviewed and semi-quantitative information on yearly changes in species abundance was collected. Overall, 75 species were mentioned by the respondents, being the most frequent citations related to warm-adapted species of both, native and exotic origin. Respondents belonging to the same biogeographic sectors described coherent spatio-temporal dynamics, and gradients along latitudinal and longitudinal axes were revealed. This information provides a more complete understanding of recent bio-geographical changes in the Mediterranean Sea and it also demonstrates that adequately structured LEK methodology might be applied successfully beyond the local scale, across national borders and jurisdictions. Acknowledging this potential through macro-regional coordination, could pave the ground for future large-scale aggregations of individual observations, increasing our potential for integrated monitoring and conservation planning at the regional or even global level.

Cabled observatories offer new opportunities to monitor species abundances at frequencies and durations never attained before. When nodes bear cameras, these may be transformed into the first sensor capable of quantifying biological activities at individual, populational, species, and community levels, if automation image processing can be sufficiently implemented. Here, we developed a binary classifier for the fish automated recognition based on Genetic Programming tested on the images provided by OBSEA EMSO testing site platform located at 20 m of depth off Vilanova i la Gertru (Spain). The performance evaluation of the automatic classifier resulted in a 78% of accuracy compared with the manual counting. Considering the huge dimension of data provided by cabled observatories and the difficulty of manual processing, we consider this result highly promising also in view of future implementation of the methodology to increase the accuracy.

The abundance and composition of fish assemblages varies at different temporal scales as a product of diel and annual rhythms. In this study, we used a video-wired observatory (OBSEA, www.obsea.es) to monitor annual rhythms in a coastal fish assemblage with a 3-year data set (2012-2014). The photographs were acquired at 30 min frequency. Five species of the family Sparidae were studied (i.e. Dentex dentex, Diplodus sargus, Diplodus vulgaris, Diplodus annularis and Diplodus puntazzo) together with water temperature and daylength. The results of the annual rhythmicity analysis indicated that most of the peaks of abundance occured in the autumn months. Results suggest differentially temporal use of the reproductive or trophic niche.