Aquatic Conservation-Marine and Freshwater Ecosystems最新文献

Nature-like fishways are an important measure for restoring fish passage, mitigating the impacts of barriers, and providing valuable habitat benefits in a more natural and effective way than traditional technical fishways. Their ecological advantages make them a preferred solution in many river restoration projects. The turbulence at the fishway's pool is a key challenge in the design of fishways. This study evaluated the hydraulic performance of the nature-like fishway section of the Zongyang Fishway Project in China. This utilized a trapezoidal cross-section with a 1:242 bottom slope, 1:2 side slopes, and an operating water depth of 1–3 m. The bottom and sides were paved with 0.2–0.5 m diameter pebbles to create suitable habitat for bottom-dwelling fish. The target design velocity was 0.7–0.9 m s⁻¹. A physical model was constructed to assess the hydraulic characteristics of the nature-like fishway, including flow velocities within the slots and turbulence levels in the pools. The results showed that the slot velocities were within the target range, the head loss was parallel to the bottom elevation, and the flow field near the bottom mimicked technical fishway conditions, whereas the surface flow resembled open channel flow. Turbulence intensity remained below 60% of the design velocity. These findings provide valuable insights into the hydraulic performance and suitability of this nature-like fishway design for facilitating fish passage of the target freshwater species along with directly aiding to SDGs 6 and 14.

1. Shipwrecks are one of the most common types of artificial reefs. They are home to several sea creatures, including sea turtles. Here, we aim to understand the relationship between sea turtles and shipwrecks by investigating species occurrence, behaviours and food availability in artificial reefs in Pernambuco, Northeast Brazil.
2. To map sea turtle occurrence in shipwrecks, we considered data from the literature, and we inspected 54,145 photos resulting from 867 recreational dives performed in 19 shipwrecks. We then selected four wrecks for systematic behavioural observations through 97 h and 56 min of passive video recordings. We also investigated potential food resources for turtles in these shipwrecks.
3. We identified three turtle species (i.e., Chelonia mydas, Eretmochelys imbricata and Caretta caretta), but most records were juvenile Chelonia mydas individuals using conserved wrecks. We recorded nine behaviours. ‘Resting’ was the predominant activity for all three species, representing over 60% of the records for all species. Their overall activity pattern varied. The wrecks were predominantly encrusted with ascidia, octocoral, sponge and algae—organisms that are part of sea turtles' diet. We highlight the ecological role of the shipwrecks for sea turtles since they may serve as shelter (especially for the juveniles of Chelonia mydas), potentially protecting them against predators and strong currents. The wrecks may also serve as potential feeding areas for sea turtles. We reinforce the need to establish appropriate regulations for recreational dive tourism in shipwrecks in Brazil to avoid disturbing sea turtles in this ecologically important artificial reef.

The assessment of wild animal welfare has recently gained interest and represents a novel, complementary approach to monitoring free-ranging populations for conservation purposes. However, few attempts have been made to develop standardized welfare assessment tools for free-ranging animals. In the present study, a preliminary scoring system for the welfare assessment of Indo-Pacific humpback dolphins (IPHDs) was created using the Five Domains Model. During a series of online meetings, the panel established the scoring unit, the contribution of each parameter to the four physical/functional domains, the inferred mental states and impact intensity associated with each of these parameters, and the method of aggregating parameter scores within and among domains. The resulting framework includes a total of 53 parameter scores. A total of 20 welfare-status and 33 welfare-alerting parameters were identified; these are aggregated into two overall welfare grades for enhancement (positive experiences) and compromise (negative experiences). The panel attributed confidence scores to the intensity impact reflected by each parameter and associated mental states. As expected, these scores reflect higher confidence in welfare-status than welfare-alerting parameters; welfare compromise was also attributed higher confidence than welfare enhancement and Domain 1 (Nutrition) globally received higher confidence scores than other domains. As with any expert elicitation study, subjective biases likely exist; these can be reduced through further research on the suggested parameters. The framework uses current knowledge and has been developed to enable continual improvement as further evidence becomes available on various parameters. This study represents an important step in the development of a welfare assessment tool (WAT) for IPHDs. Next steps include defining measurement methods and thresholds for scoring parameter intensities, followed by reliability testing. This WAT can then be used to systematically monitor populations of IPHDs in a way that will better inform conservation measures and ensure their effectiveness.

The gharial (Gavialis gangeticus), a critically endangered freshwater reptile endemic to the Indian subcontinent, faces severe threats from various anthropogenic stressors. Despite positive conservation efforts, a holistic approach is essential for improved outcomes. This involves (1) identification of new conservation priority sites, (2) establishment of gharial populations outside protected areas, (3) interlinking ecosystem processes, (4) conducting census of gharial annually, (5) efficient use of digital technology, (6) adoption of best management practices to mitigate various threats, (7) assessment of inbreeding depression in gharial, (8) rescue and rehabilitation training for local communities, (9) interstate and trans-boundary commission and (10) survey on socio-economic status of local communities. Implementing the proposed synergistic measures will not only strengthen conservation efforts but also enhance the livelihoods of local communities, ensuring a sustainable future for this species.

Rhodoliths are non-geniculate, free-living coralline red algae that can accumulate on the seafloor and form structurally complex habitats supporting highly biodiverse communities termed rhodolith beds. Limited understanding of key rhodolith kinetical attributes and how they scale with environmental variability limits ability to predict changes in rhodolith bed distribution and abundance in a globally changing ocean climate. We carried out two experiments in an oscillatory wave tank to test the effects of (1) rhodolith (Boreolithothamnion glaciale) density and wave velocity on rhodolith displacement and abrasion over a hard substratum and (2) rhodolith density on rhodolith displacement and the stability of underlying sediment. We established that on a hard substratum, (1) a threshold wave velocity of ~0.3 m s⁻¹ is required to induce noticeable displacement in average-sized rhodoliths and (2) rhodolith abrasion increases (quasi-linearly) with wave velocity up to this threshold. We also showed that (3) for a same rhodolith density, rhodolith displacement is at least two times smaller on a sedimentary than hard substratum and (4) the loss of sediment underneath rhodoliths decreases (quasi-linearly) with an increase in rhodolith density. Rates documented and strong scaling with changes in water motion and rhodolith density indicate that relatively small changes in the density of rhodoliths or hydrodynamic forces can quickly destabilize rhodolith bed frameworks and underlying sediment. These rates can be used to develop predictive models of change in rhodolith bed distribution and abundance that can in turn inform development of more accurate, science-based rhodolith bed conservation strategies.