Search

The quantity of plastic fishing gear lost to the ocean remains largely undocumented despite its importance for understanding the magnitude of fishery contributions to plastic marine debris and mitigating contamination at the source. This study estimated plastic gear loss from a major Australian pot fishery by interviewing 50 commercial fishers from the West Coast Rock Lobster Managed Fishery in 2021 to document the plastic gear components used, the number of pots lost, and the causes for gear loss. The estimated annual percentage of gear lost (10.8%) and rate of “active” gear loss by fishing effort (0.2%) were lower than global estimates for other pot fisheries indicating that plastic gear loss from this commercial fishery is relatively low. Plastic gear loss was attributed to rope (47.0%), pot components (30.7%), and floats (22.3%), of which 78.0% were polypropylene and polyethylene. The composition of pots, measures used to prevent gear loss, and changes to management could influence plastic gear loss from this fishery. This is the first study to examine plastic gear loss from an Australian pot fishery with a dynamic approach that provides robust estimates for better understanding plastic gear loss from fisheries and informing plastic mitigation efforts.

It is unknown whether lobster behaviour is sensitive to fishing, as has been previously suggested for fish. This study investigated the impacts of recreational fishing on the wariness of western rock lobster (Panulirus cygnus, George) through comparisons between fished sites and no-take reserves (NTRs) at Rottnest Island. We used visual census to survey the density and size structure of lobster at sites inside and outside three comparable NTRs, and baited remote underwater video to study the behaviour of lobster at comparable sites. The density of legal-sized P. cygnus was twice as high within NTRs (0.34 ± 0.05) than fished sites (0.16 ± 0.03). P. cygnus also spent less time with bait in fished sites (0.42 ± 0.15 min) than NTRs (1.15 ± 0.28 min). This study provides the first evidence that behaviour of decapods, namely P. cygnus, is sensitive to noninjury-related disturbance associated with recreational fishing, with higher wariness in fished areas. Investigation is required into potentially confounding biotic and abiotic factors to further explore the applicability of lobster wariness as an indicator for fishing pressure.

Many researchers have pointed to coastal environments and their use for energy production, aquaculture, and conservation as key to solving profound challenges facing humanity. Navigating this transition in ocean space necessitates tools to quantify impacts on displaced marine users, including recreational fishers. In this study, we present a novel method combining spatial ecological models of recreational catch with fine-scale random utility models of site choice to predict the impacts of site closures on recreational fishing experiences (fisher welfare). We demonstrate our approach by modelling data from over 10 000 fishing trips to fine-scale sites across 1500 km of coastline in the south-west of Australia and simulating the effects of no-take marine reserves recently implemented in the Australian Marine Parks. The results show how the combination of random utility modelling with spatial ecological methods provides a powerful tool for investigating recreational fisheries as joint social-ecological systems and incorporating recreational fishing into marine spatial planning.

Inherent differences between baited remote video versus diver-operated video survey methodologies may influence their ability to detect effects of fishing. Here, the ability of no-take zones (NTZs) to provide protection for legal-sized fish from targeted species within the Ningaloo Marine Park (NMP) was assessed using both baited remote underwater stereo-video (stereo-BRUV) and diver-operated stereo-video (stereo-DOV). The relative abundance of legal-sized individuals of three recreationally targeted fish species, spangled emperor Lethrinus nebulosus, chinaman cod Epinephelus rivulatus and goldspotted trevally Carangoides fulvoguttatus, were examined using both methodologies inside and outside six NTZs across the NMP. Stereo-BRUVs found positive effects of protection on the relative abundance of legal-size C. fulvoguttatus and L. nebulosus in NTZs. Stereo-DOVs, however, did not detect any differences in relative abundances and sizes of these species between areas opened and closed to fishing. These contrasting results suggest that choice of sampling methodology can influence interpretations of the ability of NTZs to provide adequate levels of protection for target species. Our results suggest that stereo-BRUVs are a superior technique to stereo-DOVs for assessing the effectiveness of no-take zones for protection of fishery target species, reflecting bait attraction and an absence of diver influence on fish behaviour.

Made available in DSpace on 2022-04-28T19:52:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-03-01 Fundação Grupo Boticário de Proteção à Natureza Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Visual census conducted by divers has remained the most common method for obtaining quantitative data on reef fish assemblages since it was first applied in the 1950s. More recently, stereo-video systems are increasingly becoming popular as a sampling method to complement underwater visual counts. Understanding which method is more suitable to estimate fish assemblage metrics for particular objectives and hypotheses is important to design effective studies. Here, we compared rocky reef fish assemblage characteristics sampled by diver-based stationary point count and transect visual census, as well as back and forth diver-operated stereo-video systems (stereo-DOVs) and baited remote underwater stereo-video systems (stereo-BRUVs) in a coastal island in Southwestern Atlantic. Diver-based methods sampled a higher richness and abundance of fishery non-target species closely associated with the reef, as well as cryptobenthic small-bodied species. Conversely, stereo-BRUVs’ samples focused more on larger and mobile carnivorous fishery target species of the families Carangidae and Lutjanidae. The stereo-DOV recorded higher species richness compared to other methods and required less sample effort in the field. Limitations faced by the four methods were discussed; however, the higher sampling efficiency of the adapted back and forth stereo-DOVs, combined with the diverse advantages of video techniques, such as permanent record of data and decreased interobserver variability for species identification and estimates of body size, indicates stereo-DOVs as a highly efficient method to assess the entire fish assemblage, across feeding guilds and commercially important species. In addition, when combined with a remote technique, such as stereo-BRUVs, both of these methods efficiently capture estimates of diversity metrics as well as body size information especially for fishery target species in rocky reefs. Institute of Biosciences São Paulo State University (UNESP), São Paulo Elasmobranch Research Laboratory Institute of Biosciences São Paulo State University (UNESP), São Paulo Oceans Institute and School of Biological Sciences The University of Western Australia (UWA) Department of Environmental Sciences Rural Federal University of Rio de Janeiro (UFRRJ), Rio de Janeiro Institute of Biosciences São Paulo State University (UNESP), São Paulo Elasmobranch Research Laboratory Institute of Biosciences São Paulo State University (UNESP), São Paulo Fundação Grupo Boticário de Proteção à Natureza: 1043_20151 CNPq: 141799/2016-1 CNPq: 308430/2015-8

Understanding the extent to which species’ traits mediate patterns of community assembly is key to predict the effect of natural and anthropogenic disturbances on ecosystem functioning. Here, we apply a trait-based community assembly framework to understand how four different habitat configurations (kelp forests, Sargassum spp. beds, hard corals, and turfs) shape the trophic and energetic dynamics of reef fish assemblages in a tropical–temperate transition zone. Specifically, we tested (i) the degree of trait divergence and convergence in each habitat, (ii) which traits explained variation in species’ abundances, and (iii) differences in standing biomass (kg ha−1), secondary productivity (kg ha−1 day−1) and turnover (% day−1). Fish assemblages in coral and kelp habitats displayed greater evidence of trait convergence, while turf and Sargassum spp. habitats displayed a higher degree of trait divergence, a pattern that was mostly driven by traits related to resource use and thermal affinity. This filtering effect had an imprint on the trophic and energetic dynamics of reef fishes, with turf habitats supporting higher fish biomass and productivity. However, these gains were strongly dependent on trophic guild, with herbivores/detritivores disproportionately contributing to among-habitat differences. Despite these perceived overall gains, turnover was decoupled for fishes that act as conduit of energy to higher trophic levels (i.e. microinvertivores), with coral habitats displaying higher rates of fish biomass replenishment than turf despite their lower productivity. This has important implications for biodiversity conservation and fisheries management, questioning the long-term sustainability of ecological processes and fisheries yields in increasingly altered marine habitats.