Walleye pollock (Gadus chalcogrammus, Pallas, 1814) fishery, size and age composition, state of stocks and catch prospects in the waters adjacent to Kamchatka peninsula and Northern Kuril Islands

The article provides data on the catch of the Northern Okhotsk, Eastern Kamchatka and Western Bering Sea walleye pollock stocks, fishery structure by the fishing gears in 2016–2019, size and age composition of the fish in the commercial trawl and Danish seine catches in 2010–2019. Data on the generation abundance and stock condition indices used in the stock assessment models are also demonstrated. Interannual dynamics of the total and spawning stock biomass, determinants of the dynamics and prospects of fishing are analyzed.

Long-term culture system for deep-sea mussels Gigantidas childressi

The simulation of deep-sea conditions in laboratories is technically challenging but necessary for experiments that aim at a deeper understanding of physiological mechanisms or host-symbiont interactions of deep-sea organisms. In a proof-of-concept study, we designed a recirculating system for long-term culture (>2 years) of deep-sea mussels Gigantidas childressi (previously Bathymodiolus childressi). Mussels were automatically (and safely) supplied with a maximum stable level of ~60 μM methane in seawater using a novel methane-air mixing system. Experimental animals also received daily doses of live microalgae. Condition indices of cultured G. childressi remained high over years, and low shell thickness growth could be detected, which is indicative of positive energy budgets. Using stable isotope data, we demonstrate that G. childressi in our culture system gained energy, both, from digestion of methane oxidizing endosymbionts and from digesting particulate food (microalgae). Limitations of the system, as well as opportunities for future experimental approaches involving deep-sea mussels are discussed.

Reproductive Ecology, Condition, and the Physical Environment of a Temperate Protogynous Hermaphrodite at a Small Scale

<p>Hermaphroditic reef fish display remarkable diversity in mating strategies, social structure, and the timing of sex change. Understanding spatial variation in reproductive ecology and physiological condition is important in the design of marine reserve systems and fisheries management for species that change sex. I investigated patterns in reproductive ecology, condition, and the influence of the underlying physical environment, for a temperate protogynous (female first) hermaphrodite, the spotty (Notolabrus celidotus) at a small spatial scale. First, I used SCUBA surveys to visually estimate density, sex ratio, and size-frequency to describe the social structure of two populations of spotties located at either end of a 9 km gradient in swell exposure. I then collected individuals from both locations to estimate growth, mortality, and the timing of maturation and sex change for each population. To estimate and compare physiological stress and condition of individuals sampled from these two locations, I used otoliths to quantify fluctuating asymmetry (a measure of stress) and I compared this to other commonly used condition indices. Lastly, I estimated spatial variation in social structure and a set of environmental variables at 30 sites along a gradient of swell exposure to investigate correlations between the physical environment and the density, sex ratio, and size-frequency of spotties. The results revealed that social structure differed markedly between two populations but not always as expected. A low ratio of males to females in sheltered Kau Bay suggested that the rate of sex change was constrained for this population (relative to Wahine Park, a more swell-exposed site, where males were more abundant in the population). Individuals from Kau Bay exhibited slower growth and higher mortality estimates, and in line with predictions of the size advantage model, females appeared to change sex at an early age and smaller size relative to Wahine Park. Contrary to expectations, however, low levels of fluctuating asymmetry suggested the population at Kau Bay was less stressed than Wahine Park, despite evidence for reduced physiological condition (Fulton’s condition factor K) and high density at Kau Bay. Differences in fluctuating asymmetry between sexes and size classes suggested that sex-specific fluctuating asymmetry and stressors later in the life history are important in these populations. Furthermore, correlations between social structure and the physical environment were inconclusive and highlight the necessity for large sampling efforts. Overall, this study concludes that availability of spawning-territory may limit the rate of sex change and influence reproductive potential in this species. This process may be applicable to other protogynous species that rely on territory-defense as a mating strategy. Sex-specific expression of fluctuating asymmetry should be considered in hermaphroditic reef fish and the impact of stressors acting on specific stages in the life history of individuals requires further investigation. Furthermore, my results suggest that condition indices and fluctuating asymmetry cannot be used interchangeably to estimate health for these populations (the metrics may provide complementary information). Overall, these results emphasise complex and variable patterns in the reproductive ecology of hermaphroditic species and my work is among the first to demonstrate such patterns over a small spatial scale. Further work can clarify questions raised in this study and benefit the conservation of hermaphroditic reef fish.</p>

Reproductive Ecology, Condition, and the Physical Environment of a Temperate Protogynous Hermaphrodite at a Small Scale

<p>Hermaphroditic reef fish display remarkable diversity in mating strategies, social structure, and the timing of sex change. Understanding spatial variation in reproductive ecology and physiological condition is important in the design of marine reserve systems and fisheries management for species that change sex. I investigated patterns in reproductive ecology, condition, and the influence of the underlying physical environment, for a temperate protogynous (female first) hermaphrodite, the spotty (Notolabrus celidotus) at a small spatial scale. First, I used SCUBA surveys to visually estimate density, sex ratio, and size-frequency to describe the social structure of two populations of spotties located at either end of a 9 km gradient in swell exposure. I then collected individuals from both locations to estimate growth, mortality, and the timing of maturation and sex change for each population. To estimate and compare physiological stress and condition of individuals sampled from these two locations, I used otoliths to quantify fluctuating asymmetry (a measure of stress) and I compared this to other commonly used condition indices. Lastly, I estimated spatial variation in social structure and a set of environmental variables at 30 sites along a gradient of swell exposure to investigate correlations between the physical environment and the density, sex ratio, and size-frequency of spotties. The results revealed that social structure differed markedly between two populations but not always as expected. A low ratio of males to females in sheltered Kau Bay suggested that the rate of sex change was constrained for this population (relative to Wahine Park, a more swell-exposed site, where males were more abundant in the population). Individuals from Kau Bay exhibited slower growth and higher mortality estimates, and in line with predictions of the size advantage model, females appeared to change sex at an early age and smaller size relative to Wahine Park. Contrary to expectations, however, low levels of fluctuating asymmetry suggested the population at Kau Bay was less stressed than Wahine Park, despite evidence for reduced physiological condition (Fulton’s condition factor K) and high density at Kau Bay. Differences in fluctuating asymmetry between sexes and size classes suggested that sex-specific fluctuating asymmetry and stressors later in the life history are important in these populations. Furthermore, correlations between social structure and the physical environment were inconclusive and highlight the necessity for large sampling efforts. Overall, this study concludes that availability of spawning-territory may limit the rate of sex change and influence reproductive potential in this species. This process may be applicable to other protogynous species that rely on territory-defense as a mating strategy. Sex-specific expression of fluctuating asymmetry should be considered in hermaphroditic reef fish and the impact of stressors acting on specific stages in the life history of individuals requires further investigation. Furthermore, my results suggest that condition indices and fluctuating asymmetry cannot be used interchangeably to estimate health for these populations (the metrics may provide complementary information). Overall, these results emphasise complex and variable patterns in the reproductive ecology of hermaphroditic species and my work is among the first to demonstrate such patterns over a small spatial scale. Further work can clarify questions raised in this study and benefit the conservation of hermaphroditic reef fish.</p>

Health Status Comparison of Blood Cockle (Tegillarca granosa) between Low and High Yield Farms in Selangor and Johor

This study aims to provide insight knowledge on the potential reason for low blood cockles (Tegillarca granosa) production in Sungai Buloh Selangor by comparing the condition indices and histology of the gills and gonad with samples from a high yield farm at Sungai Ayam, Johor. Samples were collected in September 2020 and grouped for histological analysis and for condition indices. About 60% individuals from Sungai Buloh and 20% of samples from Sungai Ayam found with degenerated gill filaments. The sex ratio were found identical (50%:50% male to a female) in samples from Sungai Ayam, while 40%: 60% of male to female from Sungai Buloh. The gonad of males found at Stage 2 (developing) and Stage 3 (developed or ripe) and the ovaries at Stage 3 and Stage 4 (spawning) for Sungai Buloh, and between Stage 2 to Stage 4 from Sungai Ayam. The total condition index (CI Tot) was significantly differences between farms. Findings indicate sample from Sungai Buloh has low health status due to poor gill’s filaments condition, and ripe ovaries found in lightweight (2 g) T. granosa. Hence being the potential reason for low survival rate in the Sungai Buloh.

Analysis of body condition indices reveals different ecotypes of the Antillean manatee

Assessing the body condition of wild animals is necessary to monitor the health of the population and is critical to defining a framework for conservation actions. Body condition indices (BCIs) are a non-invasive and relatively simple means to assess the health of individual animals, useful for addressing a wide variety of ecological, behavioral, and management questions. The Antillean manatee (Trichechus manatus manatus) is an endangered subspecies of the West Indian manatee, facing a wide variety of threats from mostly human-related origins. Our objective was to define specific BCIs for the subspecies that, coupled with additional health, genetic and demographic information, can be valuable to guide management decisions. Biometric measurements of 380 wild Antillean manatees captured in seven different locations within their range of distribution were obtained. From this information, we developed three BCIs (BCI1 = UG/SL, BCI2 = W/SL3, BCI3 = W/(SL*UG2)). Linear models and two-way ANCOVA tests showed significant differences of the BCIs among sexes and locations. Although our three BCIs are suitable for Antillean manatees, BCI1 is more practical as it does not require information about weight, which can be a metric logistically difficult to collect under particular circumstances. BCI1 was significantly different among environments, revealing that the phenotypic plasticity of the subspecies have originated at least two ecotypes—coastal marine and riverine—of Antillean manatees.

Monitoring Meteorological Drought in Southern China Using Remote Sensing Data

Severe meteorological drought is generally considered to lead to crop damage and loss. In this study, we created a new standard value by averaging the values distributed in the middle 30–70% instead of the traditional mean value, and we proposed a new index calculation method named Normalized Indices (NI) for meteorological drought monitoring after normalized processing. The TRMM-derived precipitation data, GLDAS-derived soil moisture data, and MODIS-derived vegetation condition data from 2003 to 2019 were used, and we compared the NI with commonly used Condition Indices (CI) and Anomalies Percentage (AP). Taking the mid-to-lower reaches of the Yangtze River (MLRYR) as an example, the drought monitoring results for paddy rice and winter wheat showed that (1) NI can monitor well the relative changes in real precipitation/soil moisture/vegetation conditions in both arid and humid regions, while meteorological drought was overestimated with CI and AP, and (2) due to the monitoring results of NI, the well-known drought event that occurred in the MLRYR from August to October 2019 had a much less severe impact on vegetation than expected. In contrast, precipitation deficiency induced an increase in sunshine and adequate heat resources, which improved crop growth in 78.8% of the area. This study discusses some restrictions of CI and AP and suggests that the new NI index calculation provides better meteorological drought monitoring in the MLRYR, thus offering a new approach for future drought monitoring studies.

Assessment of Aleutian mink disease virus (AMDV) prevalence in feral American mink in Iceland. Case study of a pending epizootiological concern in Europe

Background Recurring escapes or deliberate releases and subsequent infiltration or establishment of feral populations by individuals from fur farms have been commonly noted since the beginning of fur industry expansion. Once animals have invaded ecosystems adjacent to source farms escapees can change the demography of the feral populations through hybridization, outbreeding depression, competition and spreading of various pathogens which can decimate wild populations. In our study, we aimed to assess spread of Aleutian mink disease virus (AMDV) in the feral population of American mink (Neovison vison) in Iceland. The additional objective was to elucidate whether basic morpho-anatomical parameters (i.e., Fulton’s condition factor or spleen to body weight ratio) might be used as a preliminary indicator of AMDV infection. Methods American mink (n = 164) were captured by professional hunters in 8 regions of Iceland. The detection of AMDV in the spleen of male and female individuals was based on PCR amplification of an NS1 gene fragment. Results We confirmed AMDV presence in 23.8% (n = 39) of collected samples with no significant difference in infection rate between males and females. Additionally, we revealed that the prevalence of virus in the feral population was higher closer to fur farms. However, the countrywide prevalence and direction of AMDV distribution needs to be further investigated. Comparison of condition indices in non-infected and infected animals showed significant deterioration of body and spleen parameters in the latter group. Therefore, the application of basic measurements of the American mink may be used to evaluate the health status of individuals in terms of pathogen infection. Conclusions The study shed a new light on prevalence and distribution of AMDV in the feral population of American mink in Iceland and the results might be successfully applied to develop models to infer dynamics of various pathogens, even those latently transmitted by disease-free animals.

Survivors of Climate Driven Abalone Mass Mortality Exhibit Declines in Health and Reproduction Following Kelp Forest Collapse

Marine ecosystems are vulnerable to climate driven events such as marine heatwaves yet we have a poor understanding of whether they will collapse or recover. Kelp forests are known to be susceptible, and there has been a rise in sea urchin barrens around the world. When temperatures increase so do physiological demands while food resources decline, tightening metabolic constraints. In this case study, we examine red abalone (Haliotis rufescens) looking at sublethal impacts and their prospects for recovery within kelp forests that have shifted to sea urchin barrens. Abalone are a recreationally fished species that once thrived in northern California’s bull kelp forests but have recently suffered mass mortalities since the 2014–2016 marine heatwave. Quantitative data exist on the health and reproduction of abalone both prior to and after the collapse. The survivors of the mass mortality show a 2-year lag in body and gonad condition indices. After the lag, body and gonad indexes decreased substantially, as did the relationship between shell length and body weight. Production of mature eggs per female declined by 99% (p &lt; 0.001), and the number of eggs per gram of female body weight (2,984/g) declined to near zero (9/g). The number of males with sperm was reduced by 33%, and the sperm abundance score was reduced by 28% (p = 0.414). We observed that these reductions were for mature eggs and sperm while immature eggs and spermatids were still present in large numbers. In the lab, after reintroduction of kelp, weight gains were quickly lost following a second starvation period. This example illustrates how climate-driven declines in foundation species can suppress recovery of the system by impacting body condition and future reproduction of surviving individuals. Given the poor reproductive potential of the remaining abalone in northern California, coupled with ongoing mortality and low kelp abundances, we discuss the need to maintain the fishing moratorium and implement active abalone restoration measures. For fished species, such as abalone, this additional hurdle to recovery imposed by changes in climate is critical to understand and incorporate into resource management and restoration.