Movements and diving behaviour of white-chinned petrels: Diurnal variation and implications for bycatch mitigation

1. Many seabirds dive to forage, and the ability to use this hunting technique varies according to such factors as morphology, physiology, prey availability, and ambient light levels. Proficient divers are more able to seize sinking baits deployed by longline fishing vessels and may return them to the surface, increasing exposure of other species. Hence, diving ability has major implications for mitigating incidental mortality (bycatch) in fisheries.
2. Here, the diving behaviour and activity patterns of the most bycaught seabird species worldwide, the white-chinned petrel (Procellaria aequinoctialis), tracked from Bird Island (South Georgia), are analysed. Three data sources (dives, spatial movements, and immersion events) are combined to examine diverse aspects of at-sea foraging behaviour, and their implications for alternative approaches to bycatch mitigation are considered.
3. The tracked white-chinned petrels (n = 14) mostly performed shallow dives (<3 m deep) of very short duration (<5 s), predominantly during darkness, but only 7 and 10% of landings in daylight and darkness, respectively, involved diving, suggesting that surface-seizing is the preferred foraging technique. Nonetheless, individuals were able to dive to considerable depth (max = 14.5 m) and at speed (max = 2.0 m·s⁻¹), underlining the importance of using heavy line-weighting to maximize hook sink rates, and bird-scaring lines (Tori lines) that extend for long distances behind vessels to protect hooks until beyond diving depths.

     

Recreational scuba diving in a groundwater ecosystem: Disturbance mechanisms,ecological impacts and stakeholder perceptions

1. Ecological damage by scuba divers has been extensively studied in marine ecosystems, particularly coral reefs, whereas the impacts on freshwater environments such as groundwater springs is unknown. In the Silfra groundwater fissure in Iceland, a vast increase in diver entries has occurred during the last decade, prompting concerns over potential ecosystem impacts and visitor carrying capacity.
2. Here, a mixed‐method approach was used to assess the impacts of scuba diving in Silfra. (a) Divers were recorded under water to observe the mechanisms of diver‐related disturbances, (b) benthic material was collected along transects in Silfra and the undisturbed fissure Flosagjá to compare biofilm biomass and zoobenthic communities between and within fissures, and (c) the perceptions and experiences of stakeholders surrounding the dive tourism in Silfra were explored.
3. Underwater observations showed that 91.4% of the divers caused at least a single disturbance, resulting in biofilm detachments and/or sediment stirring. Diver fins caused the most frequent disturbances, predominantly through fin‐generated currents but also by directly contacting the substrate. Benthic biofilm biomass was lower in Silfra than Flosagjá and exhibited a negative correlation with dive‐use. Some disturbance‐tolerant zoobenthic groups exhibited moderate to strong correlations with dive‐use.
4. All stakeholders had negative perceptions towards increasing diver entries, but although entry limitation could improve tourism quality, disturbance might only minimally be reduced as springs like Silfra may be particularly sensitive.
5. Springs are characteristically stable and uniform environments that can be vulnerable to disturbance. Their use for scuba diving should be carefully managed through a holistic approach and an active collaboration between all stakeholders.

     

Diving behaviour of a Baird's beaked whale, Berardius bairdii, in the slope water region of the western North Pacific: first dive records using a data logger

A depth and temperature data logger was deployed by air gun on an individual Baird’s beaked whale (Berardius bairdii) off the Pacific coast of Japan. The retrieved data logger recorded 81 dives over approximately 29 h. The maximum recorded depth and the longest dive duration were 1777 m and 64.4 min, respectively. All dives were classified into three categories by depth: deep dives (>1000 m), intermediate dives (100–1000 m), and shallow dives (<100 m). Several intermediate dives generally followed a deep dive, and sequential shallow dives followed several intermediate dives in the record of the Baird’s beaked whale.     

Diving for science ‐ science for diving: volunteer scuba divers support science and conservation in the Mediterranean Sea

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Bycatch susceptibility in pelagic longline fisheries: are albatrosses affected by the diving behaviour of medium‐sized petrels?

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Are changing diver characteristics important for coral reef conservation?

1. the 2012 industry has a higher proportion of low and medium specialization visitors that have lower expectations and lower overall satisfaction, yet remain willing to return;
2. the average per capita economic contribution of divers to the local economy and to dive companies declined by more than 30% by 2012;
3. Andaman coast diving continued to grow in 2012, dominated by mass ‐ market tourism that had diversified into several niches;
4. the results verify the use of the Wildlife Tourism Model as a tool to understand industry sustainability, and suggest further development of the model to capture the extension into specific, niche markets.

Changes to diver characteristics in 2012 restrict the ability of diving to fund conservation, provide alternative livelihoods, support environmental choices by operators, and control dive pressure exerted on reefs.

Results suggest the operationalization of Limits of Acceptable Change by both managers and dive operators to grow the conservation value of diving.

The results of this study suggest that the Wildlife Tourism Model can be used to inform management choices in emerging dive destinations. For instance, creating spatial zones that target the tourist composition most appropriate to meet the conservation goals of each reef system.

Copyright © 2015 John Wiley & Sons, Ltd.     

Why do young Pacific bluefin tuna repeatedly dive to depths through the thermocline?

Young Pacific bluefin tuna Thunnus orientalis with archival tags were released in the East China Sea. Time-series data for depth, and ambient and peritoneal temperatures for nine fish, recorded every 128 s, were analyzed. Our objectives were to describe monthly changes in diving patterns in relation to the ambient thermal structure and the occurrence of feeding events during March–June, and to discuss possible reasons why bluefin tuna repeatedly dived to depths below the thermocline in terms of their thermoconservation mechanisms. It was found that the fish repeatedly dived through the thermocline at intervals of 1.2 h on average, and the dive frequency was high during March–May. However, the dive frequency and periodicity decreased in June, when the gradient became steeper. In contrast, feeding events increased in June. These results indicate that from March to May, bluefin tuna repeatedly dive because food biomass is inadequate at the surface, and they stop undertaking repeated dives in June when food becomes more readily available at the surface, in addition to low visibility caused by low solar radiation. Further, the range of heat transfer times for these fish was so long that their peritoneal temperature was probably maintained by engaging in brief dives. The periodicity of dives may lead to a lower fluctuation in the peritoneal temperature, suggesting that the dives are a kind of behavioral thermoregulation.     

Survival of rockhopper penguins in times of global climate change

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Benthic communities in the Southwest Atlantic Ocean: Conservation value of animal forests at the Burdwood Bank slope

1. The characterization of benthic communities at the Burdwood Bank slope (≥200 m depth) is provided, comprising data from the marine protected area (MPA) Namuncurá II (created in December 2018), as well as from some deep bathyal surrounding areas in the Southwest Atlantic Ocean. This information was acquired during two research cruises with RV Puerto Deseado (Argentina) during 2016 and 2017.
2. Marine animal forests were detected in the study area: coral gardens, mainly composed of alcyonaceans, were detected in the south and west of Burdwood Bank (MPA Namuncurá II) and neighbouring areas, whereas pennatulacean aggregations were detected in the north‐west of the plateau. The three‐dimensional structures of live but also dead corals provide substrate and refuge to many associated species. Benthic communities dominated by sponges were also recorded between 200 and 300 m in depth.
3. Six sites that meet the characteristics of vulnerable marine ecosystems (VMEs) are reported.
4. Conservation strategies applied to scarcely known austral Argentinean waters led to the establishment of a pioneer MPA (Namuncurá I). Following the management plan that aimed to establish the biodiversity of Namuncurá I and neighbouring areas, the area of protection has now been enlarged to include the southern slope of the bank (currently Namuncurá II), where marine animal forests were detected, at depths below 200 m. The data presented here provide empirical evidence to support the conservation value of the region.

     

Effects of depth and eutrophication on the zooxanthella clades of Stylophora pistillata from the Gulf of Eilat (Red Sea)

• 1. The symbiotic association between corals and zooxanthellae has been a major contributing factor in the success of reef‐building corals.
• 2. The diversity of zooxanthellae harboured in the hermatypic coral Stylophora pistillata in the Gulf of Eilat (Aqaba), northern Red Sea, was investigated on the basis of the length and sequence variation of the 18S small subunit ribosomal DNA. Of several clades found worldwide, only clades A and C were found to be associated with this coral species in the Gulf.
• 3. No correlation between the pink and brown colour morphs of the coral S. pistillata and the zooxanthella clade was found. Shallow‐water colonies (5 m) harbour clade A while deeper‐water colonies (17 m) harbour either clade A or C. This coral is a brooding species that associates with different zooxanthellae at different depths.
• 4. Eutrophication from fish farms did not affect clade identity associated with Stylophora.

Copyright © 2008 John Wiley & Sons, Ltd.     

Assessing the importance of net colour as a seabird bycatch mitigation measure in gillnet fishing

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A new large‐scale and cost‐effective restoration method for cold‐water coral gardens

1. Gorgonians dwelling on the Mediterranean continental shelf are among the most frequent fishing bycatch taxa. These species display several traits, such as long lifespans and slow growth, which make them very vulnerable to the impacts caused by fishing activities with far‐reaching and long‐lasting effects.
2. Hence, restoration and mitigation actions are crucial to enhance and speed up the natural recovery of damaged cold‐water coral gardens. Given the growing concern to develop effective and affordable restoration actions, the present study aims to propose and technically validate a new large‐scale and cost‐effective restoration method.
3. This technique, named ‘badminton method', consists of attaching bycatch Eunicella cavolini colonies to cobble supports and returning them to the continental shelf by gently throwing the gorgonian transplants directly from a boat.
4. Two consecutive field experiments were conducted in order to find the best cobble type support and gorgonian size to be used: first, to evaluate the landing efficiency of gorgonian transplants at different depths (from 5 to 30 m) and second, to evaluate their capability to maintain a correct position over time.
5. Natural cobbles with large gorgonians attached were the best option. Field results and modelling approaches suggest that the transplants would correctly land on the continental shelf seabed in a predicted area of around 60 m². Moreover, they would successfully maintain an upright position ensuring gorgonian survival over time.
6. The success of this method highlights the feasibility of large‐scale and low‐cost restoration actions with promising results for the conservation and recovery of cold‐water coral gardens.

     

Considerations on diving patterns of bigeye tuna Thunnus obesus based on archival tag data

Swimming depth and selected environmental factors were examined using 2764 days of archival tag data for 18 bigeye tuna Thunnus obesus (fork length at release 58.5 ± 7.2 cm) that were captured, tagged, and released into Japanese waters. Daytime swimming depth was deeper with increasing body length. The lowest temperature encountered was usually about 10 °C or slightly higher. A positive correlation between swimming depth and light intensity at the ocean surface was dominant for during both daytime and nighttime. Synchronicity of swimming depth with deep scattering layer (DSL) was observed, except around midday. Deep diving to depths exceeding 550 m was observed a mean of 0.30 dives/fish/day. Based on the classification and analyses of deep diving pattern and consideration of environmental data, deep diving was assumed to be undertaken for the purposes of foraging, predator avoidance, and exploration of bathymetry, as well as due to aberrant behavior. Occasionally, extremely deep diving events exceeding 1000 m (maximum 1616 m) were recorded. Bigeye tuna appear to have high visual acuity and tolerance of both low and wide temperature ranges, and low dissolved oxygen content. Thus, probably bigeye tuna swimming depth is primarily adjusted based on prey distribution.     

The marine temperature and depth preferences of Arctic charr (Salvelinus alpinus) and sea trout (Salmo trutta), as recorded by data storage tags

Eleven Arctic charr (Salvelinus alpinus) (370–512 mm) and eight sea trout (Salmo trutta) (370–585 mm in length) were tagged externally or internally with depth‐ and temperature‐measuring data‐storage tags (DST) before they were released into the sea in the Alta Fjord in north Norway in June 2002. All sea trout were recaptured after they spent 1–40 days at sea, while all Arctic charr were recaptured after 0.5–33 days at sea. On average, trout preferred water about 0.6 m deeper and 1.3°C warmer than Arctic charr. Arctic charr spent >50% of their time between 0 and 1 m depth, while trout spent >50% of their time between 1 and 2 m depth. Both species spent >90% of their time in water no deeper than 3 m from the water surface. However, sea trout dove more frequently and to greater depths (max. 28 m) than Arctic charr (max. 16 m), and these deep dives were most frequently performed at the end of the sea migration. Arctic charr demonstrated a diel diving pattern, staying on average about 0.5 m deeper between 08:00 hours and about 15:00 hours than during the rest of the 24 h, even though there was continuous daylight during the experiments. When comparing data obtained from the DSTs with temperature measurements within the fjord system, the two species were observed to select different feeding areas during their sea migration, the sea trout choosing the inner and warmer parts of the fjord, in contrast to the Arctic charr that preferred the outer, colder parts of the fjord. The observed differences in migration behaviour between the two species are discussed in relation to species preferences for prey and habitat selection, and their optimal temperatures for growth.     

Do surrogates describe patterns in marine macroalgal diversity in the Recherche Archipelago,temperate Australia?

• 1. Surrogates aim to predict species diversity and to minimize sampling effort. Here the value of surrogates for marine macroalgae is tested.
• 2. Higher taxonomic levels and dominant taxa were evaluated as surrogates for detecting patterns in macroalgal species diversity (derived from species‐level biomass data) in the Recherche Archipelago, Western Australia.
• 3. Data were stratified by two island groups (inshore and offshore), three depth intervals (<10 m, 10–20 m, >20 m), and two exposures to wave energy. Correlations between similarity matrices from surrogate and species diversity data matrices were analysed using a modified Spearman rank correlation (r_s). The ability of surrogates to detect differences between exposures to wave energy was also investigated using analysis of similarity. Species diversity data were aggregated to higher taxonomic levels and were either fourth‐root or presence/absence (richness) transformed.
• 4. Species richness was the most consistent surrogate (r_s‐values>0.69, P=0.001). Genus‐level richness was also strongly correlated to species diversity in the Recherche Archipelago, except in depths <10 m where patterns in diversity were characterized by species turnover.
• 5. At offshore islands in depths 10–20 m and >20 m, family‐ and order‐level biomass data were suitable surrogates owing to the abundance of Alariaceae (Order Laminariales) represented by a single genus and species. Surrogates using biomass data from the orders Laminariales, Ceramiales, Dictyotales and Fucales were also successful at offshore islands in middle to deeper depths.
• 6. At inshore islands in depths 10–20 m and >20 m, genera from the orders Gigartinales, Fucales and Ceramiales were strongly correlated to species biomass data.
• 7. Surrogates, like species richness, that were strongly correlated to species biomass data were also able to distinguish between exposures to wave energy, based on analysis of similarity tests.
• 8. Sampling effort would be reduced if collecting richness data in species‐rich macroalgal assemblages such as those found in temperate Australia.

Copyright © 2006 John Wiley & Sons, Ltd.     

Testing a depth‐based Habitat Classification System against reef fish assemblage patterns in a subtropical marine park

• 1. The Solitary Islands Marine Park (SIMP) in New South Wales (NSW), Australia, has strong cross‐shelf patterns of reef fish assemblages on shallow reefs (<25 m). While the SIMP also contains reef at depths of up to 75 m, marine communities below 25 m are poorly described. The Habitat Classification System (HCS) used for planning the arrangement of zones in this marine park included three depth categories for reef: shallow (<25 m); intermediate (25–60 m); and deep (>60 m). However, these had not been tested to determine if they adequately reflect biotic patterns.
• 2. Using baited remote underwater video (BRUV), fish assemblages were surveyed at 56 sites spread across shallow, intermediate, and deep reefs within the SIMP to examine spatial variation between depth categories. Relationships between assemblage patterns, depth, and four additional factors considered likely to affect assemblage patterns (distance from shore, reef type, dominant benthos, and latitude), were subsequently explored using multivariate statistical methods.
• 3. Reef fish assemblages differed significantly among the depth categories. Assemblage patterns for fish were strongly correlated with depth and moderately correlated with the dominant benthic assemblage. Correlations with the other factors were generally weak. Three distinct assemblages occurred on reefs <25 m, 25–50 m and >50 m. Shallow (<25 m) reefs also displayed strong cross‐shelf patterns, supporting the results from other studies. Weaker cross‐shelf patterns were evident at intermediate depths (25–50 m).
• 4. Depth‐based and cross‐shelf categories are clearly fundamental components for a HCS that will adequately represent reef fish assemblages for conservation planning in the SIMP. Further refining the depth criteria for the intermediate/deep boundary (to 50 m) improves this representation. Further research is required to determine the wider application of the refined HCS to other marine parks in NSW and to determine how well it represents other components of biodiversity. Copyright © 2011 John Wiley & Sons, Ltd.

     

Coastal breeding aggregations of threatened stingrays and guitarfish in the Levant

1. Stingrays and guitarfish are globally threatened by overexploitation, particularly so in the Mediterranean Sea. Nevertheless, very little information is known about their ecology, behaviour, and taxonomy in the Mediterranean, and especially in the Levant, where water temperature, salinity, and the impact of invasive species are relatively high.
2. Although it has been suggested that some species may aggregate in the Levant, this has not been formally documented and the scale of this phenomenon, the taxonomic composition, and the temporal dynamics are unknown.
3. Visual surveys were conducted, which allowed the documentation of stingrays and guitarfish behaviour, and which was not available from data based on fishery catches. The census took place within a marine protected area over a period of 3 years.
4. Altogether, we documented 675 batoid observations. One of the observed species is Endangered (Glaucostegus cemiculus) and one is Vulnerable (Dasyatis pastinaca), whereas the others are classed as Least Concern (Torpedo torpedo and Torpedo marmorata), Data Deficient (Taeniurops grabatus), non‐assessed within the Mediterranean (Dasyatis chrysonota), and Not Evaluated (Himantura uarnak). Results show clear seasonal patterns, with dense aggregations recorded during spring and early summer, when densities reached 85 observations per kilometre. In addition, there were clear indications of breeding behaviour in D. pastinaca and D. chrysonota, including the first recorded documentation of D. pastinaca courtship in the Mediterranean.
5. Large seasonal stingrays and guitarfish aggregations in shallow waters have not, to our knowledge, been documented in the Mediterranean Sea previously. This highlights the importance of conserving shallow habitats as potential breeding grounds. As these sites are easily reached while both snorkelling and diving, the aggregation of these charismatic species can serve as potential ecotourism sites. Finally, this study shows the benefits of using simple visual census, as opposed to catch‐based methods, to record both the diversity and the behaviour of batoids.

     

Decimation of a population of the endangered species Scutellastra mexicana (Broderip and Sowerby, 1829) (Mollusca,Gastropoda) in the Marías Island (Eastern Ocean Pacific) Biosphere Reserve

1. Scutellastra mexicana is the largest known patellid limpet species and probably is one of the most endangered marine invertebrates.
2. The species was once distributed along the American Pacific coast from Mexico to Peru, but their large size (up to 35 cm long) and easy accessibility (shallow sublittoral), made it very vulnerable to human collection and now is extinct on most of the mainland Mexican coast.
3. In August 2017, a large population of this species was found on María Cleofas island, off the coast of west‐central Mexico (Marías Archipelago, Pacific Ocean). This constitutes the only report of a population of this species since 1988.
4. A total of 808 adult individuals of up to 26 cm in length and 20 cm in width were estimated, together with the presence of juveniles, suggesting that it is a self‐sustaining population. The population was monitored in August 2017 and August 2018.
5. Although the species is under the category ‘Special Protection’ in the General Mexican Wild Law, and that María Cleofas island is a Biosphere Reserve, fishermen that operate with impunity in the area decimated the limpet population within a year of its discovery. Abundance in the shallowest area decreased significantly from 120 individuals per transect (65 m long and 2.75 m wide) in August 2017 to 48 individuals in August 2018, and the estimated adult population decreased from 808 to 304 limpets.
6. Neither passive national conservation policies nor local practices have reduced current threats to biodiversity and resource depletion in Marías Archipelago. Protected areas like this are ‘paper parks’—parks in name only—because there is no active conservation strategy or protection of marine species.

     

Tori‐lines with weighted branch lines reduce seabird bycatch in eastern South Pacific longline fishery

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