Fishing Areas Research Articles

Using benthic recruitment densities to forecast fisheries recruitment of American lobster in Atlantic Canada

There is limited understanding of the mechanisms underlying the marked spatial and temporal trends in landings of American lobster in Canada since the mid-1980s, and little ability to forecast changes. We built an individual-based model for three Lobster Fishing Areas (LFAs) in Canada that uses the annual density of benthic recruits in nursery grounds to generate an index of exploited biomass 6 to 10 years in the future, using von Bertalanffy growth equations complemented with inter-individual variability in growth, and regional maturity ogives and spawning probabilities to allow exclusion of ovigerous females from the exploitable biomass. We found significant positive relationships between the modelled biomass index and fisheries landings in all three LFAs. Out-of-sample validation in two LFAs (longer time series) using 1-year and 6-year reduced data sets revealed mean annual prediction errors of 11.4% and 11.2%, and 23.7% and 51.7%, respectively. Our findings strongly suggest benthic recruitment indices could help make strategic decisions concerning lobster fishing activities, and they argue for the continued and expanded monitoring of lobster benthic recruitment in Canada.

Evaluasi Bangunan Pelindung Pantai Sisi Miring Dalam Upaya Penanggulangan Abrasi Pesisir Pantai

The coast of Kampung Jawa Lama, Banda Sakti Sub-district, Lhokseumawe City is a fishing area and densely populated. The breakwater building in the coastal area of Kampung Jawa Lama is a sloping Breakwater with a height of 1.5 m and a width of 1 m. The type of breakwater used is usually determinet by the availability of material on the site. The problem in this research was the cause of abrasion and its impact, as well as how to plant coastal protection structures. The purpose of this study was to reduce the impact of erosion, abrasion and damage to the buildings and to re-evaluate coastal structures. The method used on this research is Hudson method and descriptive analysis by making direct observation and reviuwing research that has been done previously. The cause of abrasion is triggered by several factors such us tides, high sea waves and ocean currents that have the potential to cause damage as a result of strong winds that produce destructive waves. The community also receiver the impact of the abrasion, namely decreasing income, the place where they live is inundated by sea water and it affects the decline in the quality of life of the community. One of the efforts that can be applied to reduce the abrasion problem in the area is to build a Breakwater construction. Based on calculation, the results obtained in the planning reviuw of the existing shoreline protection building were 1.5 m, so that to prevent abrasion the increase in height of the building 4.074 m was 5.574 m with a peak width of 1 m so that increase of 0.20 m was 1.2 m, the thickness of the first layer of protection was 1.2 m and the thickness of the second layer was 0.60 m. The width of the leg guard is 1.8 m with a thickness of 0.5 m

Integration of socio-ecological data to prioritize biodiversity hot-spots for Marine Protected Area (MPA) delineation in the coastal zone of Bangladesh

Marine Protected Areas (MPAs) are widely used tools for conserving coastal and marine biodiversity and ecosystem health. However, the goal of declaring and managing at least 10 % of coastal and marine waters as MPAs has not been achieved in Bangladesh and many other countries. This study aimed at prioritizing the potential areas for MPA delineation in the south-west coastal zone of Bangladesh. The study also examined the socio-economic status, environmental and ecological characteristics of the study areas. Data on socio-economic, environmental, ecological, and management variables were collected through intensive field surveys from August 2023 to December 2023. The data were integrated using a multi-criteria analytical technique. Fishing was identified as the primary occupation for all fishermen surveyed, with secondary occupations including fish selling, marketing, and drying activities. The fishing areas for fishermen from the three survey sites were mainly concentrated in the offshore area. All three areas were identified as biodiversity hotspots, with Kuakata coast showing the highest species diversity, followed by Salimpur and Sandwip coasts. The study revealed that the Kuakata coast has the highest conservation importance, especially for IUCN red-listed species, juvenile fisheries species, and megafauna species. Salimpur coast is important for the conservation of saltmarshes, mangroves, and their dependent communities, while Sandwip is crucial for juvenile fish species conservation. Based on socio-ecological criteria, Kuakata was recommended as the most potential site for MPA delineation, followed by Salimpur and Sandwip. Implementing these recommendations can improve the management and execution of existing MPAs by focusing conservation efforts on areas with the highest biodiversity and ecological importance, ensuring better protection for vulnerable species, and enhancing the sustainability of local fishing communities. This, in turn, will ultimately enhance biodiversity conservation and ecosystem health in the southwest coastal area of Bangladesh.

Emergent geopolitical risks from fishing activities and past conflicts in the Pacific Ocean

Pacific Ocean longline fisheries support numerous international fleets targeting various species. However, global fishing activities has increased the density of vessels flagged to different countries fishing near each other. Such spatial competition increases the risk of fisheries conflicts by potentially introducing resource sharing, gear interactions, or territorial disputes. As international fisheries conflicts increase and fishing patterns evolve, it is important to know who is fishing nearby whom, and where. Enduring rivalries, or countries with historical disputes, can also contribute to a cycle of future conflicts. Here, we use network and geospatial analyses to examine which countries, country pairs, and regions in the Pacific Ocean may be at an elevated risk of fisheries conflict from spatial competition and enduring rivalries. Certain countries dominate fishing activities: Taiwan and Chinese-flagged vessels fish the largest area at 64 million km2 each (33 % greater than the next ranked country), with 7.9 and 7.2 million fishing hours respectively (nearly 2 times greater than the next ranked country). These countries and others (Japan, United States, South Korea) rank among the highest in conflict risk because of large overlapping fishing areas with enduring rivals. International diversity is most widespread in the tropical Pacific, though highest in the south Pacific, reflecting international participation in tropical bigeye and yellowfin fisheries and south albacore fisheries. High-risk regions primarily occur in the tropical Pacific across jurisdictions and similarly appear influenced by regional fisheries management. Overall, our research takes an international-level approach to study how spatial and temporal interconnectedness may influence conflict risk.

Marine protected areas can increase the abundance of invasive lionfish (Pterois miles)

AbstractMarine protected areas (MPAs) can protect and restore marine biodiversity and fisheries, but there are concerns that they may also benefit invasive species. The spatial and temporal colonization of invasive lionfish (Pterois miles) in the eastern Mediterranean was compared across zones with varying fishing restrictions (no fishing, recreational and commercial fishing, and commercial fishing only), and stations where targeted removal events were conducted by volunteer SCUBA divers. Lionfish density in no fishing areas was nearly double that of areas with commercial fishing only, and over four times greater than in areas where both commercial and recreational fishing were allowed. Lionfish density increased with depth, possibly due to easier human exploitation in shallow waters (0–10 m) that are accessible to recreational spearfishers. Targeted removals by volunteer divers decreased lionfish densities by over 60%, while areas without removals had a 200%–400% increase. Along with management actions, natural and ecological processes might drive lionfish densities within MPAs, and the speed with which lionfish colonized fishery‐restricted zones, emphasized the need for a more sophisticated MPA management strategy that considers invasive species impacts and dynamics in an ecosystem‐based approach.

Analysis of recommendations for developing sustainable fishing areas based on geographic information systems: the integrated Center of Marine and Fisheries (SKPT) Mimika case study

Abstract The Integrated Center of Marine and Fisheries (SKPT) is one of the Indonesian government’s steps in developing better management of the fisheries sector. SKPT Mimika has “The golden fishing ground” waters with a capture fisheries potential of 2.64 million tons per year; Arafura waters are one of the most fertile waters in Indonesia. With this potential and the concept of water development, namely the blue economy, where the economy with the axis of the sea must be sustainable, has a high urgency to ensure that there is no excessive exploitation of marine resources. The development of a sustainable blue economy involves many parties, but we consider that the closest community is the answer to the success of this development. Creating the potential fishing zone (PFZ) from Aqua MODIS image data and SWOT Analysis to formulate sustainable recommendations can help the community and stakeholders. Some of the outcomes of our recommendations are 1) Empower and implement an adaptive management approach that considers the needs and situations of each member of society, community, and region; 2) Increase the resilience of fisheries and aquaculture systems through implementing sustainable practices, diversifying fisheries commodities, and increasing access to markets. 3) Increase the ability of fisheries and aquaculture stakeholders to adapt to the impacts of climate change through training, education and awareness-raising activities; 4) Integrate the fisheries and aquaculture sectors into national policies and strategies for climate change; and 5) Management of intentional fishing and dumping.

KOMPOSISI HASIL TANGKAPAN GILLNET MILENIUM BERDASARKAN PERBEDAAN KEDALAMAN SETTING DIPERAIRAN PULAU AMBON

The natural dynamics of the distribution of fish resources in marine waters are not uniform. This will have implications for optimizing the utilization of fish resources using various fishing gear in a fishing area. Fishing using millennium gillnets is generally not done by many fishermen on Ambon Island. The research aimed to determine the composition and influence of differences in millennium gillnet depth on catch results. This research method is a fishing experiment using 3 units of 3.5-inch millennium gillnets of uniform size which are set on the bottom of the water at treatment depths, namely 0-20 meters, 21-40 meters and > 40 meters. Simultaneous capture operations in the afternoon for 8 capture attempts. During the research, the catch was 364 fish weighing 209 kg. 6 types of fish were identified, namely Kuwe (Caranx sexfasciatus), yellow-tailed Lalosi (Caesio cunning), sand porter (Naso thynnoides), Samandar (Siganus sp), and grouper (Epinephelus merra), and mackerel (Scomberomorus gullatus). This type of fish is usually found swimming in open water or near the sea surface. The highest number of catches was the Kuwe fish species, 135 fish (37.09%) weighing 56.4 kg (26.99%), the lowest was the Tenggiri fish species (Scomberomorus gullatus), 5 fish (1.37%) weighing 5.1 kg (2, 44%). The highest catch was in the 21-40 m depth range, namely 162 fish and 94.7 kg, followed by more than 41 m, namely 103 fish and 57 kg, and the lowest in the 0-20 m depth range, namely 99 fish and 57.3 kg. The chance of catching fish occurs at all net-setting depths, but the highest chance occurs at 21-40 m. The results of the analysis showed that neither the overall catch nor the dominant fish species showed significant differences based on differences in depth.

Sustainable management of predatory fish affected by an Allee effect through marine protected areas and taxation

Ecological balance and stable economic development are crucial for the fishery. This study proposes a predator–prey system for marine communities, where the growth of predators follows the Allee effect and takes into account the rapid fluctuations in resource prices caused by supply and demand. The system predicts the existence of catastrophic equilibrium, which may lead to the extinction of prey, consequently leading to the extinction of predators, but fishing efforts remain high. Marine protected areas are established near fishing areas to avoid such situations. Fish migrate rapidly between these two areas and are only harvested in the nonprotected areas. A three-dimensional simplified model is derived by applying variable aggregation to describe the variation of global variables on a slow time scale. To seek conditions to avoid species extinction and maintain sustainable fishing activities, the existence of positive equilibrium points and their local stability are explored based on the simplified model. Moreover, the long-term impact of establishing marine protected areas and levying taxes based on unit catch on fishery dynamics is studied, and the optimal tax policy is obtained by applying Pontryagin’s maximum principle. The theoretical analysis and numerical examples of this study demonstrate the comprehensive effectiveness of increasing the proportion of marine protected areas and controlling taxes on the sustainable development of fishery.

Evaluating the influence of marine protected areas on surf zone fish.

Marine protected areas (MPAs) globally serve conservation and fisheries management goals, generating positive effects in some marine ecosystems. Surf zones and sandy beaches, critical ecotones bridging land and sea, play a pivotal role in the life cycles of numerous fish species and serve as prime areas for subsistence and recreational fishing. Despite their significance, these areas remain understudied when evaluating the effects of MPAs. We compared surf zone fish assemblages inside and outside MPAs across 3 bioregions in California (USA). Using seines and baited remote underwater videos (BRUVs), we found differences in surf zone fish inside and outside MPAs in one region. Inside south region MPAs, we observed higher abundance (Tukey's honest significant difference [HSD]=0.83, p=0.0001) and richness (HSD=0.22, p=0.0001) in BRUVs and greater biomass (HSD=0.32, p=0.0002) in seine surveys compared with reference sites. Selected live-bearing, fished taxa were positively affected by MPAs. Elasmobranchs displayed greater abundance in BRUV surveys and higher biomass in seine surveys inside south region MPAs (HSD=0.35, p=0.0003 and HSD=0.23, p=0.008, respectively). Although we observed no overall MPA signal for Embiotocidae, abundances of juvenile and large adult barred surfperch (Amphistichus argenteus), the most abundant fished species, were higher inside MPAs (K-S test D=0.19, p<0.0001). Influence of habitat characteristics on MPA performance indicated surf zone width was positively associated with fish abundance and biomass but negatively associated with richness. The south region had the largest positive effect size on all MPA performance metrics. Our findings underscored the variability in species richness and composition across regions and survey methods that significantly affected differences observed inside and outside MPAs. A comprehensive assessment of MPA performance should consider specific taxa, their distribution, and the effects of habitat factors and geography.

The catch amount of Mediterranean horse mackerel Trachurus mediterraneus (Steindachner, 1868) gillnets in the Sea of Marmara

The small-scale fishermen in the coastal area of the Marmara Sea between April and June caught the Mediterranean horse mackerel Trachurus mediterraneus (Steindachner, 1868) with gillnets. This target species, T.mediterraneus and significant amounts of non-target species are caught in these nets. So, the technical and structural characteristics of the gillnets for a commercial fishermen were determined and the target and non-target species were evaluated in catching operations. The multifilament gillnet mesh size of 18 milimeters polyamid, twine thickness of 210d/2, hanging ratio of 0.33 and the total length of approximately 200 meters. Also, guarding nets were added to gillnets. The total amount was determined as 397.8 kilograms (kg) and 9204 individuals (ind). The weight of T.mediterraneus was constituted 39.3% of the total weight. The in of T.mediterraneus was constituted 43.4% of the total ind. While the catch per unit effort (CPUE) for T.mediterraneus was calculated at 0.026 kg/m.operation-1 and 0.7 ind/m.operation-1, the CPUE for the total amount was calculated at 0.066 kg/m.operation-1 and 1.5 ind/m.operation-1. The total economic value was calculated at 15814.4 Turkish Liras (TL), which 9390 TL from T.mediterraneus and 6424.4 TL from non-target species. This study is important in terms of revealing for the first time the catch efficiency of gillnets used by commercial fishermen to catch T.mediterraneus in the coastal area of the Marmara Sea, which is an important fishing area. These results will contribute to the creation of management plans and fisheries management for species-specific fishing gear used in a region.

Comparison of linear and nonlinear modeling approaches to develop an abundance index based on voyage and market data for a data-limited fishery

IntroductionWorldwide coastal fish resources face severe threats from fisheries overexploitation. However, the evaluation of abundance trends in most coastal fisheries is constrained by limited data. This study took blackmouth croaker (Atrobucca nibe), a stock depleted by coastal trawl fishery in southwestern Taiwan, as an example to showcase the development of a relative abundance index from data-limited fishery (only landing data were available).MethodsThis study employed unique data sourcing from voyage data recorders (VDRs) to estimate fishing effort (in combination with landing data to estimate the catch per unit effort, CPUE) that demonstrated the potential application in global data-limited fisheries and assessed alternative approaches for predictors of fishery-targeting practices to condition effort for producing more accurate metrics of relative abundance. The nominal CPUE was standardized using three statistical models: generalized linear model, generalized additive model (GAM), and vector-autoregressive spatiotemporal models (VASTs) with two treatments of each of the four effects: environmental (sea temperature, salinity, density of mixing layer, seafloor temperature, and chlorophyll), vessel, spatial, and targeting effects. A total of 15 models were designed and compared for these effects, and their explanatory power (EP) was evaluated using cross-validation R2 and other metrics.Results and discussionResults indicated that the targeting effect exerted the most significant influence on standardization and was suggested to be addressed through the principal component analysis (PCA) approach. Both vessel and spatial effects demonstrated considerable influence, whereas the environmental effect exhibited a limited impact, possibly due to the small fishing area in this study. Regarding models’ EP, given the nonlinear nature of the PCA algorithm and environmental data, the study highlighted the superiority of the GAM over linear-based models. However, incorporating nonlinear features in VAST (M15) makes it the most effective model in terms of predictive power in this study. Concerning the stock status, despite variations in relative CPUE trends among major models, a general declining trend since 2015 signals the potential decline of the blackmouth stock and urges fishery managers to consider further design of management measures.

MANAGEMENT PLAN FOR RECREATIONAL FISHING IN THE HYDROGRAPHIC ÂNCORA RIVER BASIN

This work is the result of the most recent studies carried out by the ICNF in the drainage basin of the future recreational fishing area (ZPL) of the Âncora river. These supported the design of a plan for the sustainable management and exploitation of recreational fishing in this river basin, which is part of the Minho and Lima Hydrographic Region (RH1). Seven sampling stations were set up for this purpose. Six in the main watercourse and one in the Regueiro dos Enxurros, in the middle of an area of successive waterfalls, just before its confluence with the Regueiro da Lapa Ladrão, which is considered to be the source of the Âncora River. At these stations, hydromorphological quality assessments were carried out on 500 m stretches using the River Habitat Survey (RHS) methodology and fish community monitoring (three per station, for a total of twenty-one inventories) using the electrofishing technique. The results made it possible to consider implementing more sustainable management and exploitation measures for fishing in these continental bodies of water. In this context, the management options took marked account of conservation objectives associated with the presence of European eels (Anguilla anguilla) and red eels (Achondrostoma spp.), the wide distribution of trout (Salmo trutta) and the reduced presence of boga (Pseudochondrostoma duriense) whose distribution in the upper third of this drainage basin is conditioned by a very peculiar geomorphology, filled with numerous slopes, which give rise to beautiful waterfalls. With the information collected, data on the age, growth and physical condition of the ichthyofauna assessed was studied, and their relationship with the different types of habitat in which they occurred was established. The results show that these are watercourses with "Excellent" quality habitats, but with levels of artificialization ranging from "severely modified" to "predominantly unmodified", the result of anthropogenic actions over time. Trout (Salmo trutta) are the most widely distributed species along the main watercourse. The absence of exotic aquaculture species in the samples and the lack of medium to large water impoundment structures in the hydrographic network evaluated should be emphasized. The existing river compartmentalization is materialized by the numerous micro-weirs (many of which allow aquatic organisms to migrate for a good part of the year) and a few waterfalls (natural cascades) that prevent fish from passing through. The trout show isometric growth for all the sampling stations, a balanced physical robustness and a maximum lifespan of 6 years. As a practical result of this study, a Recreational Fishing Management and Exploration Plan for the Âncora River will be created, which will support the design of measures to promote the sustainable management of recreational fishing in the area of the future LPZ, reconciling this activity with nature conservation objectives.

Assessing the Conservation Value of Artificial and Natural Reefs via Ichthyoplankton Spatio-Temporal Dynamics

The distribution of fish eggs and larvae (ichthyoplankton) reflects spawning and nursery areas as well as dispersal routes. This study’s goal is to demonstrate how the identification of ichthyoplankton species and stages and their spatial distribution among natural reefs (NRs) and artificial reefs (ARs) may serve as decision-making tools in conservation and fishery management. Natural reefs exhibited an eight-times higher abundance of eggs, as well as the highest abundance of larvae in the yolk-sac and preflexion phases. In contrast, ARs had the highest abundance of larvae in the flexion and postflexion phases. Natural reefs may serve as breeding grounds for Scaridae, Labridae, and Mugilidae; whereas, ARs may serve as breeding sites for Lutjanidae, Synodontidae, Carangidae, Fistularidae, and Haemulidae. Our study revealed differences between ARs and NRs, which demonstrate the potential of artificial reefs to expand the supply and settlement options of reef fishes and consequently can lead to increased fish production with potential benefits to adjacent fishing areas through connectivity. Thus, ARs as no-take sites can be effective tools for both fishery management and biodiversity conservation. The findings highlight the potential use of ichthyoplankton tools and the importance of considering both types of reefs in marine conservation and management efforts.

Defining the role of Sabellaria alveolata reefs as nursery areas for juvenile fish: first evidence from drone-based imagery and underwater visual census data

The biogenic reefs built by the honeycomb worm Sabellaria alveolata constitute priority habitats along Atlanto-Mediterranean coastal areas. Despite their wide extent and important ecological role, the nursery value of S. alveolata reefs remains unclear, and more information is needed to define how such structured habitats affect juvenile fish assemblages. In this study, habitat use by juveniles of 7 fish species was investigated by underwater visual census (UVC) at 3 study sites representing a gradient of complexity of Sabellaria reef habitats, spanning from a large and uniform reef to patchy and isolated small reef formations. Sabellaria reef metrics derived by drone-based cartography and GIS analysis were used to quantitatively monitor the seasonal structural changes occurring due to the natural dynamics of the reefs. We also tested the potential effect of Sabellaria habitats on the growth and relative condition factor (Kn) of white seabream Diplodus sargus juveniles. Five of the 7 surveyed species, especially sparid fishes, showed a clear preferential association with Sabellaria formations. Generalized additive modelling revealed a significant effect of the compactness ratio on estimated fish densities at high and low index values. The juvenile fish sampled on Sabellaria reefs exhibited higher values of Kn than those sampled on rocky habitats, supporting the hypothesis that structural complexity positively affected their condition. We provide evidence on habitat use by juveniles, suggesting that the presence of the Sabellaria reef may act as a nursery and affect local fish density in Mediterranean coastal waters.

Technical and Financial Analysis of Floating Lift Net Business in Tulehu Village, Central Maluku Regency

Uncertainty of sustainability is a common problem in the fisheries business due to the nature of the fishes, which are seasonal and highly perishable. Therefore, financial analysis of this kind of business is essential to maintain its sustainability. Many small-scale fishing businesses requires an organized financial record keeping. This research is aimed at (1). Analyze the technical conditions of the floating lift net business in Tulehu Village, Central Maluku Regency, and (2) Analyze the financial aspects of the floating lift net business in Tulehu Village, Central Maluku Regency. The results show that the floating lift net in Tulehu Village measured 18m x 20m, with the construction parts consisting of a balancer, lift net house, support poles, net rollers, and anchor rollers, while the parts of the additional equipment which consist of nets, lighting devices, boats, and transport machines as well as scoops. The average number of fishing activities for floating lift nets in non-fishing seasons is 55 trips, while in the fishing season, it is 138 trips, with different fishing areas depending on the season. Based on the investment assessment criteria, the average R/C calculation value is 3.4, the average PP value is 3.26, and the average ROI value is 34.87%. The floating lift net business at the research location is financially feasible to develop.

Erosion vs. accretion of sandy beaches: their impacts on nursery areas of coral reef fish

Erosion vs. accretion of sandy beaches: their impacts on nursery areas of coral reef fish

Comparative Study on Current Fishing Status of Paalameenmadu and Kallar Barmouths in Batticaloa District,

Batticaloa lagoon is one of the productive estuaries on the East coast of Sri Lanka and is connected to the sea at two points, Paalameenmadu and Kallar barmouths. The entire dynamics of the lagoon is based on the seasonal opening and closing of the above barmouths which influences the fish catch composition in nearby fishing areas. This study collects information on current fishing practices, species composition of the catch, and seasonal catch species composition, the level of awareness on fishing regulation and sustainable fishery using semi-structured questionnaire. Fisheries data were collected from 10 major barmouth fishery landing sites from January to April 2021. 210 respondents were selected using a stratified random sampling technique. A semi-structured questionnaire was used to collect responses after a pre-test and analysed with descriptive statistics method using SPSS. The study revealed that Paalameenmadu barmouth was opened annually and Kallar barmouth has been closed for the last five years. The most practiced crafts in Paalameenmadu are outboard Fiber Reinforced Plastic boats (OFRP) by 35.26% of fishers and small lagoon canoes by 87.04% fishers in Kallar. A total of seven types of fishing gears are used, among them hook and line, cast net, and dragnet were identified as major fishing gears operated. 30 aquatic species have been recorded in the catch, representing 17 families. Among them, dominant fish families are Scombridae 17.11% and Penaeidae 14.81% in Paalameenmadu. In the Kallar, family Penaeidae 18.75% and Gerreidae 16.32% have been recorded. Barmouth opening is favourable for fishing and 38.57% Penaeidae species were caught during barmouth opening period. Community response that Irregular and early barmouth opening have caused a reduction in fish production which impacts on economic activities. Fishermen have good awareness on importance of fishery resources sustainability and these resources need to be preserved for future generations through proper management practices.

Characterization of hypoxic events in Paracas bay (Peru, 13.8°S) through intensity and biological effect indexes

Over the past decade, there has been a significant increase in low oxygen conditions within marine coastal areas, profoundly impacting ecosystem processes and living coastal resources. Coastal bays in highly productive upwelling regions, where hypoxia occurs naturally, are special areas affected by both local and adjacent shelf-related processes. Paracas Bay (13.8°S) is a traditional shellfish fishing and intense farming area highly influenced by one of the most active upwelling centers of the Peruvian coast. Despite the small dimensions of the bay (35 km2), a key feature is its complex physical dynamics and high environmental variability. Recently, important efforts have been made in the study of both the spatial and temporal oxygen concentration variability, nevertheless, information regarding the ecological and biological impact of hypoxic events is still lacking. In this study, the spatial and temporal distribution of hypoxic events was analyzed across Paracas bay at different depths by means of high-frequency hourly dissolved oxygen records collected by data-loggers deployed across the bay during the periods September 2012 – February 2013 and March 2015 – February 2017. To study the ecological impact of hypoxic events, we developed a hypoxia intensity index, while the biological impact was studied through the development of a hypoxia biological effect index using as model species the Peruvian scallop (Argopecten purpuratus). Our results showed that hypoxic events have an intrinsic variability across the bay. The deeper areas of the bay, towards the northwest and center, were characterized by long, intense, and lethal events, while the southeast and southwest, shallower areas, were characterized by shorter events of low intensity and either sublethal or innocuous. We propose that the observed variability is not only related to the large-scale environmental context in which the events occurred, but also to small-scale variability linked to local circulation, biological activity, and sediment biogeochemistry. We expect that our research will be useful not only for scientific purposes, but also for coastal resource management and aquaculture, underlining the importance of developing high-resolution oxygen monitoring systems in coastal bays.

Quantification of finfish assemblages associated with mussel and seaweed farms in southwest UK provides evidence of potential benefits to fisheries

Low trophic aquaculture, including shellfish and seaweed farming, offers a potentially sustainable food source and may provide additional environmental benefits, including the creation of new feeding, breeding and nursery areas for fish of commercial and ecological importance. However, quantitative assessments of fish assemblages associated with aquaculture sites are lacking. We used pelagic baited remote underwater videos (BRUVs) and hook and line catches to survey summer fish assemblages at 2 integrated blue mussel Mytilus edulis and kelp (predominantly Saccharina latissima) farms in southwest UK. We recorded at least 11 finfish species across the surveys, including several of commercial importance, with farmed mussels and/or kelps supporting significantly higher levels of abundance and richness than reference areas outside farm infrastructure. Farmed kelp provided temporary habitat due to seasonal harvesting schedules, whereas farmed mussels provided greater habitat stability due to overlapping interannual growth cycles. Stomach content analysis of fish caught at the farms revealed that some low trophic level species had high proportions of amphipods in their stomachs, which also dominated epibiont assemblages at the farms. Higher trophic level fish stomachs contained several lower trophic level fish species, suggesting that farms provide new foraging grounds and support secondary and tertiary production. Although not identified to species level, juvenile fish were abundant at both farms, suggesting potential provisioning of nursery or breeding grounds; however, this needs further verification. Overall, this study provides evidence that shellfish and seaweed aquaculture can support and enhance populations of commercially and ecologically important fish species through habitat provisioning.

Estimating the extent of urchin barrens and kelp forest loss in northeastern Aotearoa, New Zealand

ABSTRACT On shallow rocky reefs in northeastern Aotearoa, New Zealand, urchin barrens are indicators of the ecosystem effects of overfishing reef predators. Yet, information on their extent and variability is lacking. We use aerial imagery to map the urchin barrens and kelp forests on reefs (<30 m depth) across seven locations, including two long-established marine reserves and a marine protected area that allows recreational fishing. Urchin barrens were present in all locations and were restricted to reefs <10–16 m deep. Urchin barrens covered 30% (7–49%) of shallow reefs in fished areas, with variation among and within locations likely related to the relative extent and topography of reefs and wave exposure. Within the marine reserves, barrens covered <2% of shallow reefs. Long-term comparison of historical imagery at two fished locations demonstrates that current areas of urchin barrens were historically dominated by kelp forests, but barrens have persisted since at least the early 2000s. We estimate ∼30 km2 of barrens exist across the region. This demonstrates the widespread nature of barrens, the potential long-term effectiveness of no-take marine protection in restoring urchin barrens, and the need for a multifaceted management approach to restore kelp forests and prevent further expansion of barrens.