Exploring foraging preference of local fish species towards non-indigenous fouling communities near marinas: Insights from Remote Video Foraging System (RVFS) trials.

Non-indigenous species (NIS) spread from marinas to natural environments is influenced by niche availability, habitat suitability, and local biotic resistance. This study explores the effect of indigenous fish feeding behaviour on NIS proliferation using fouling communities, pre-grown on settlement plates, as two distinct, representative models: one from NIS-rich marinas and the other from areas outside marinas with fewer NIS. These plates were mounted on a Remote Video Foraging System (RVFS) near three marinas on Madeira Island. After 24-h, NIS abundance was reduced by 3.5 %. Canthigaster capistrata's preference for marinas plates suggests potential biotic resistance. However, Sparisoma cretense showed equal biting frequencies for both plate types. The cryptogenic ascidian Trididemnum cereum was the preferred target for the fish. Our study introduces a global framework using RVFS for in-situ experiments, replicable across divers contexts (e.g., feeding behaviour, biotic resistance), which can be complemented by metabarcoding and isotopic analysis to confirm consumption patterns.

Effect of underwater visual survey methodology on bias and precision of fish counts: a simulation approach.

Bias in underwater visual census has always been elusive. In fact, the choice of sampling method and the behavioural traits of fish are two of the most important factors affecting bias, but they are still treated separately, which leads to arbitrarily chosen sampling methods. FishCensus, a two-dimensional agent-based model with realistic fish movement, was used to simulate problematic behavioural traits in SCUBA diving visual census methods and understand how sampling methodology affects the precision and bias of counts. Using a fixed true density of 0.3 fish/m2 and a fixed visibility of 6 m, 10 counts were simulated for several combinations of parameters for transects (length, width, speed) and point counts (radius, rotation speed, time), generating trait-specific heatmaps for bias and precision. In general, point counts had higher bias and were less precise than transects. Fish attracted to divers led to the highest bias, while cryptic fish had the most accurate counts. For point counts, increasing survey time increased bias and variability, increasing radius reduced bias for most traits but increased bias in the case of fish that avoid divers. Rotation speed did not have a significant effect in general, but it increased bias for fish that avoid divers. Wider and longer transects and a faster swim speed are beneficial when sampling mobile species, but a narrower, shorter transect with a slow swim is beneficial for cryptic fish.

Ecological quality assessment of small estuaries from the Portuguese coast based on fish assemblages indices.

The importance of establishing the ecological quality of estuarine systems has been widely acknowledged and led to the development of several fish community-based multimetric indices. Nevertheless, a question rose about the accuracy of these tools when natural disturbance is acting upon the organization of the systems' communities. Four multimetric indices were used to examine their ability to differentiate the ecological status of five small estuarine systems (southern Portugal), and also to test if they reflected the level of anthropogenic pressures. Fish assemblages from Mira, Odeceixe and Aljezur (in the Southwest coast), Gilão and Bensafrim (in the South coast) estuaries were sampled seasonally for one year, and anthropogenic sources of pressure were identified and quantified. We found that although the applied indices provided information on ecological condition differentiation among systems, they are unable to explain different classes of ecological status in systems with equivalent pressure levels.

Development of a fish-based multimetric index to assess the ecological quality of marine habitats: the Marine Fish Community Index.

In this paper the Marine Fish Community Index (MFCI) for the assessment of ecological status of marine environment is proposed. The MFCI was divided into 4 typologies: Rocky subtidal; shallow, intermediate and deep soft-bottoms. Based on the typical community associated to each typology and the DPSIR analysis performed, a set of metrics were selected and tested through a multiple correlation matrix (Pearson's coefficient) and the core ones included in the index. The MFCI was applied in all typologies and the scores obtained with each metric were analyzed. In order to test the robustness of the MFCI the final ecological value of each zone was recalculated by removing successively one metric at a time. The MFCI showed a sensitive and robust response in the ecological status assessment. Since it incorporates both functional and structural community information, the MFCI can be useful in the context of the Marine Strategy Framework Directive as well as in other contexts of conservation and sustainable management of the marine environment.

Efficacy of adapted estuarine fish-based multimetric indices as tools for evaluating ecological status of the marine environment.

The assessment of ecological status of marine fish communities required by the marine strategy framework directive (MSFD) emphasises the need for fish-based ecological indices in marine waters. In this study we adapt five estuarine multimetric indices to the marine environment and apply them in three types of substrates, analysing the metrics responsible for the obtained patterns of ecological status. The results show inefficiency of the community degradation index (CDI) and the biological health index (BHI) in ecological status assessment and disagreement between the estuarine biotic integrity index (EBI), the estuarine fish community index (EFCI) and the transitional fish classification index (TFCI). Analysis of individual metrics suggests lack of representativeness and consideration for the particularities of each substrate's typical fish communities. None of the tested indices were efficient on the marine environment, urging the need for new marine indices that account for differences between types of substrate and depth.