Marine and Freshwater Research最新文献

Entrainment and removal of fish from aquatic ecosystems can occur at water pump offtakes. Exclusion screens that reduce these impacts are recognised as an important conservation measure.

Evaluate the effectiveness of the Australian screen design guidelines in protecting larvae and young-of-year age class of a native fish species, Murray cod Maccullochella peelii.

Entrainment and impingement of postflexion larvae and young-of-year were assessed in a controlled laboratory environment. Tests were conducted under a range of approach velocities (AV) and impingement durations for two screen materials.

Fish screens reduced larval entrainment by ≤84%. Screens had no significant effect on reducing larval entrainment at AV ≥0.125 m s⁻¹. Impingement of young-of-year was positively associated with AV and mortality increased with impingement duration, irrespective of screen type.

To protect early life-stage Murray cod, it is recommended that water pump offtakes be fitted with 2-mm vertical wedge-wire stainless steel screens and AV be limited to ≤0.1 m s⁻¹.

This study represents the first assessment of the effectiveness of the Australian screen design guidelines in protecting larvae, providing knowledge to further refine specifications for screen design and support the recovery of native fish populations.

Longspined sea urchins (Centrostephanus rodgersii) form extensive urchin barrens in south-eastern Australia, threatening biodiversity and lucrative fishery stocks. Although large urchins are readily visible on reefs, small or ‘undersized’ urchins have often been considered non-emergent, cryptic, and largely inaccessible to predators, meaning smaller predators are considered not to contribute to top–down urchin control.

Here, we aim to investigate variation in nocturnal movement across urchin size classes and discuss the associated ecological implications.

Using timelapse footage we measured timing of movement, distance covered, and displacement of different sized sea urchins in various habitats.

Small urchins emerge from cryptic habitats and are active overnight on open reef areas. At dusk, smaller urchins emerge later than larger urchins, whereas at dawn, movement of all size classes of urchins decline at a similar rate.

The nocturnal emergence and movement of small urchins on open reef spaces makes them accessible to nocturnal predators, such as the southern rock lobster (Jasus edwardsii).

This time–space overlap of predator and prey implies that rock lobsters (including small lobsters) may be inflicting higher predatory pressure than previously considered on undersized sea urchins.

The Mediterranean fanworm arrived as a non-indigenous species in parts of Australasia, where it has established and then rapidly spread from the initial points of arrival, despite marked differences in environmental conditions compared from its natal habitat in the Mediterranean Sea.

To better understand the invasive capacity of this species in New Zealand.

Maturation, reproductive cycle, and gametogenesis were investigated, with a focus on female gamete development, for a population in Auckland, and the results were compared with those of previous studies in the Mediterranean Sea and Australia.

Egg sizes in female fanworms were highly variable throughout the year; however, a reduced presence of larger eggs was observed from August to November, which could indicate spawning. This Auckland fanworm population also appeared to have a female-skewed sex ratio compared with previous studies where a 1:1 sex ratio was observed. Fanworm maturation was reached at ~6 cm in length, compared with 15 cm in natal populations. Fanworms with body size smaller than 5 cm were not mature and did not produce mature gametes, in contrast to an Australian fanworm population.

The observed Mediterranean fanworm population in New Zealand demonstrates reproductive flexibility and high fecundity, contributing to its invasive capacity.

The reproductive biology of a species is important in determining its invasive capacity, and may also be flexible between populations, with implications for effective biosecurity management strategies.

Rioraja agassizii is a vulnerable species endemic to the Southwest Atlantic. It is caught by trawl fisheries throughout its range.

To determine the age, estimate growth parameters, and age and size at maturity.

Ages were determined using vertebrae readings. To fit growth models, a Bayesian framework was employed with the von Bertalanffy, Gompertz and Logistic candidate models. To estimate age and size at maturity, a logistical ogive was fitted to binomial maturity data.

Maximum ages determined for males and females were 12 and 11 years respectively. The von Bertalanffy model was selected as the best one and there were no differences between sexes (mean parameters: L_∞ = 684.8 mm, k = 0.33 years⁻¹ and L₀ = 105.5 mm). Age and size at maturity were estimated at 3.31 and 4.55 years, and 485.02 and 544.55 mm TL for males and females respectively.

Rioraja agassizii has a moderate growth rate and age at maturity was similar to those of skate species with a similar body size.

Because skate species have different maximum ages, growth rates and maturity parameters, we strongly recommend urgent species-specific management measures for the pool of skate species exploited in Argentina.

Diseases have affected coral populations worldwide, leading to population declines and requiring active restoration efforts.

Describe population and individual impacts of necrotising disease in the Endangered octocoral Dendronephthya australis.

We quantified population loss and recruitment by using reference photos, survey and GPS mapping and described disease lesions by using histopathology.

From December 2019 to January 2020, we observed polyp loss, necrotic lesions and loss of large colonies of D. australis at Botany Bay, New South Wales, Australia. By September 2020, only a few scattered recruits remained, and all large colonies were lost. Histopathology of colonies sampled in January 2020 confirmed that the disease had resulted in necrosis, gastrovascular canal collapse and internal colony integrity loss, leading to mortality. New recruits were recorded within 10 months of disease onset, and large colonies within 18 months.

Although the necrotising disease had significant impacts on both the individual and population level, natural recruitment began quickly. As such, unlike in other populations, restoration is not currently required in the Bare Island D. australis population.

The extent of disease impact at the individual and population levels suggests that monitoring for lesions should be undertaken before developing conservation and restoration strategies for this species.

Otoliths are calcified structures in the inner ear of fish, the analysis of which can be used to derive important life-history characteristics. Otoliths can be used to age young fish by counting daily growth increments visible in the otolith cross-section; however, this is costly and time-consuming. Otolith weight is a potential surrogate for fish age in growth analysis, providing a rapid alternative. Bony bream (Nematalosa erebi) is Australia’s most widespread freshwater fish and an important component of riverine food webs, yet its life-history characteristics are informed by few publications. We investigated the relationship between assumed fish age derived from otolith increments and otolith weight in young-of-year bony bream. We also assessed the utility of otolith weight for use in relative growth rate analysis. Linear modelling showed a significant positive relationship between increment count and otolith weight. Otolith weight when paired with body length was a reliable alternative to increment count, and thus age, for use in relative growth studies. This method can facilitate research into the factors shaping the life history of this ecologically significant species.

Aquaculture is an essential industry and assessing its impact on the environment, particularly water quality, is crucial for sustainable practices. This study aimed to comprehensively evaluate the seawater quality in the Dongji Island yellow croaker (Larimichthys crocea) aquaculture area by using the fuzzy comprehensive evaluation method and field survey.

The main objective of this study was to assess the seawater quality in the aquaculture area during 2 consecutive years (2019 and 2020) on the basis of monitoring data.

The researchers utilised the fuzzy comprehensive evaluation method to assess seawater quality in the Dongji Island yellow croaker aquaculture area. Seawater monitoring data from 6 months in 2019 and 6 months in 2020 were collected for the evaluation. The method included an annual average evaluation, and membership degrees were calculated for each year and individual months. Qualitative interviews with 30 local fish farmers were conducted to unravel the challenges faced by aquaculture water quality management.

The evaluation results indicated that the seawater quality in the aquaculture area was classified as Class I water in both 2019 and 2020 on the basis of the annual average evaluation. However, the membership degrees for 2019 were higher than those for 2020, suggesting that water quality was better in 2019. Furthermore, individual monthly evaluations in 2020 showed varying membership degrees, with May and June having higher membership degrees, indicating better water quality than in other months. August had the lowest membership degree, implying poorer water quality during that month.

The study demonstrated that the fuzzy comprehensive evaluation method is effective for evaluating seawater quality in aquaculture areas. It also concluded that the water quality in 2019 was superior to that in 2020, raising concerns about potential environmental degradation.

The quantitative and qualitative findings of this research have important implications for aquaculture practices in the Zhoushan area. The study highlights the need for continued monitoring and management of water quality to ensure sustainable aquaculture practices and adherence to water-quality policies. Future aquaculture endeavours in the region should consider the potential impact on water quality to maintain a healthy ecosystem.

The usual strategy for monitoring of eutrophication process is the use of traditional limnological methods, based on laboratory analysis. These procedures involve costly and time-consuming analyses, usually with in vitro methodologies, which can still have limitations in terms of sensitivity and reliability, if poorly managed. Phytoplankton pigments, such as chlorophyll-a (Chl-a), are highly fluorescent and can provide the environmental status of water bodies.

This study aims to analyse, compare and evaluate an estimation of Chl-a through fluorescence in public water sources in the Brazilian cerrado. Exploratory statistical analyses were conducted by using absolute fluorescence units (AFU) and relative fluorescence units (RFU) compared with traditional laboratory data (standard procedure for the determination of Chl-a by spectroscopic methods) to evaluate the significance of differences in estimating Chl-a concentration. Subsequently, empirical models, based on spectral band combinations, were generated to convert fluorescence measurement in Chl-a concentration, by linear regression.

The generated model found a strong correlation and coefficient of determination (r = 0.88; R² = 0.78). The efficiency of the model was also confirmed by statistical indicators (RMSE = 1.27, MAPE = 26.72 and BIAS = −6.32).

We concluded that the estimate of Chl-a through RFU was better than through AFU.

Therefore, based on the results of this study, it is recommended that RFU be used to obtain more precise and accurate estimates of Chl-a concentration through empirical models based on linear regression.

Poorly installed or undersized culverts at road crossings are one of the most frequently encountered barriers to fish movements, especially for small-bodied fish species. Although replacement with more ‘fish friendly’ culvert designs is the preferred solution, at many sites remediation will be required in the short to medium term. Consequently, there is a need for effective evidence-based fish passage solutions that can be deployed at scale. This study examined the passage efficiency of juvenile īnanga (Galaxias maculatus) past a perched culvert fitted with spat ropes and a flexible rubber ramp. Only four fish (0.79%) successfully passed the ramp, and no fish successfully passed the whole culvert by the conclusion of the trial. Deployment of flexible rubber ramps to remediate fish passage at perched culverts has recently become common practice in several regions of New Zealand, despite the absence of any evidence base to support their use. This study provides a strong preliminary indication that flexible rubber ramps are an ineffective fish passage solution for remediating perched culverts for non-climbing fishes. To overcome low head-migration barriers, there are alternative evidence-based fish ramp designs, which practitioners can have considerably greater confidence in for achieving restoration goals.

In recent years, Phaeocystis globosa has become a typical red tide species in the Beibu Gulf, posing a safety hazard to the cold-water intake system of the Guangxi Fangchenggang Nuclear Power Plant.

To establish an effective early risk-warning monitoring and ensure the safety of nuclear power plant cold-water intakes.

In this study, a multifactor and multilevel early risk-warning monitoring system was established using the early warning idea of ‘risk grading’.

The results showed that this method can analyse the influence trend of marine-environment changes on the growth of P. globosa and improve the timeliness of early warning and forecasting.

The method established in this paper can effectively guide coastal nuclear power enterprises to conduct early risk warning and monitoring of P. globosa and improve the accuracy of early warning and forecasting.

The methed is of great significance to coastal nuclear power enterprises dealing with red tide disasters caused by P. globosa blooms.