Antitumor activity is one characteristic function of some certain antimicrobial peptides (AMPs) found in recent years. In the present study, we attempted to detect potential anticancer activity of a recombinant piscidin 5-like from Larimichthys crocea (rLc-P5L) which owned widely antibacterial and strong antiparasitic activity in vitro. The light microscope observation indicated rLc-P5L was of antitumor activity to HeLa cells, 293T cells and L929 cells. MTT assay showed the toxic sensitivity of rLc-P5L to three tumor cell strains was 293T>L929>HeLa. Scanning electron microscope (SEM) results showed rLc-P5L behaved like a lytic peptide to cause damage on cells membrane of L929 cells by forming globular clusters, even pores at 60 μmol/L, or degrading membrane to make it completely lose cytoskeleton structure at 80 μmol/L; rLc-P5L treatment also resulted in DNA degradation. Fluorescence observation results indicated rLc-P5L could cause L929 cells at least two obvious changes: one is nucleus, nuclear chromatin condensed in the margin, nuclear volume became smaller and shrank to be out of shape, or lysed to be debris; the other is cytoskeleton, they became disordered and polarized to make cells atrophic shapes, or even lysed to be debris. In summary, rLc-P5L owned potential anticancer activity causing membrane structure damage and genome DNA degradation. Interestingly, treatment with different concentration of rLc-P5L seemingly caused the similar but different changes, whether it indeed gave rise to cancer cells diverse death way, the further studies should be performed, and the detailed mechanisms were still need further explored.

The majority of fishery stocks in the world are data limited, which limits formal stock assessments. Identifying the impacts of input data on stock assessment is critical for improving stock assessment and developing precautionary management strategies. We compare catch advice obtained from applications of various data-limited methods (DLMs) with forecasted catch advice from existing data-rich stock assessment models for the Indian Ocean bigeye tuna (Thunnus obesus). Our goal was to evaluate the consistency of catch advice derived from data-rich methods and data-limited approaches when only a subset of data is available. The Stock Synthesis (SS) results were treated as benchmarks for comparison because they reflect the most comprehensive and best possible scientific information of the stock. This study indicated that although the DLMs examined appeared robust for the Indian Ocean bigeye tuna, the implied catch advice differed between data-limited approaches and the current assessment, due to different data inputs and model assumptions. Most DLMs tended to provide more optimistic catch advice compared with the SS, which was mostly influenced by historical catches, current abundance and depletion estimates, and natural mortality, but was less sensitive to life-history parameters (particularly those related to growth). This study highlights the utility of DLMs and their implications on catch advice for the management of tuna stocks.

In contrast to typical planktonic hydromedusae, Cladonema medusae are mostly benthic, with specialised adhesive branches to adhere to the substrate. In this study, a Cladonema species discovered in a laboratory aquarium in Fuzhou, China, was confirmed as a new species, based on morphological and molecular analyses. The species was named Cladonema multiramosum sp. nov. Its medusa is distinct from that of congeners possessing substantially more adhesive branches (8–24, rarely 5–7), and tiny branches on the upper radial canals. The validity of C. multiramosumum sp. nov. was also supported by molecular phylogenetic analyses based on the mitochondrial 16S rDNA sequence. However, C. multiramosum sp. nov. medusa also displayed considerable phenotypic plasticity with respect to its radial canals, tentacles, stinging branches per tentacle, oral tentacles, manubrium, and gonads, hindering species identification based solely on morphology. Although some morphological characteristics of hydroids (filiform tentacles and medusa buds) and nematocysts could also be used as diagnostic characters in the genus Cladonema, this information is unavailable for some Cladonema species. Thus, the taxonomy within the genus Cladonema was re-evaluated based mainly on the morphological characteristics of the medusa. Further revision of the genus Cladonema should be made when supplementary information on the life cycle and DNA barcoding are updated.

A new spectrophotometric method based on a liquid waveguide capillary cell for an enhanced detection was developed to measure nanomolar iodate concentrations. This method has a detection limit and precision of 1–2 nmol/L, which is equivalent to 10% that of conventional methods, a recovery of 97.7%–104.0%, and a working range of 10–120 nmol/L. Water samples were collected from three estuaries and one coastal ocean for testing, and the proposed technique detected as low as 11 nmol/L and 18 nmol/L iodate in these samples. This newly developed method is helpful in understanding the biogeochemical cycle of iodine in nature.

Fixed-station sampling design was widely used in fishery-independent surveys because of its characteristics of convenient sampling station setting, but the non-probabilistic (fixed) nature made it more uncertainty of drawing inferences on population. The performance of fixed-station sampling design for multispecies survey has not been evaluated, and we are uncertain if the design could detect the temporal trends of different populations in multispecies fishery-independent survey. In this study, spatial distribution of abundance indices for three species with different spatial distribution patterns including small yellow croaker (Larimichthys polyactis), whitespotted conger (Conger myriaster) and Fang’s blenny (Enedrias fangi) were simulated using ordinary kriging interpolation as the “true” population distribution. The performance of fixed-station sampling design was compared with simple random sampling design by resampling the simulated “true” populations in this simulation study. The results showed that the fixed-station sampling design had the power to detect the seasonal trends of species abundance. The effectiveness of fixed-station sampling design were different in different species distribution patterns. When the species had even distribution, fixed-station sampling design could get high quality abundance data; when the distribution was uneven with heterogeneity or patchiness, fixed-station sampling design tended to underestimate or overestimate the abundance. Evidently, the estimates of abundance index based on the fixed-station sampling design must be calibrated cautiously while applying them for fisheries stock assessment and management. This study suggested that fixed-station sampling design could catch the temporal dynamics of population abundance, but the abundance estimates from the fixed-station sampling design could not be treated as the absolute estimates of populations.

Long-term variations in population structure, growth, mortality, length at median sexual maturity, and exploitation rate of threadfin bream (Nemipterus virgatus) are reported based on bottom trawl survey data collected during 1960–2012 in the Beibu Gulf, South China Sea. Laboratory-based analyses were conducted on 16791 individuals collected quarterly in eight different sampling years. Average body length, estimated asymptotic length, and percentage of large individuals have decreased significantly with the growth of marine catch and fishing power, indicating individual miniaturization of this fish species. Estimated exploitation rates indicate that the N. virgatus stock in the Beibu Gulf was moderately exploited in 1960 and 1962 and overexploited after 1992. This stock was taking a good turn in status in 2012, with the lowest exploitation rate since 1992 and ceased downward trend in length indexes. These results suggest that management measures to reduce fishing pressure may have a positive influence on the biological characteristics of this commercial fish species. Biological characteristics of most commercial fish species have phenotypic plasticity and might change over years in response to fisheries management. Therefore, attentions should be paid on variations in fish biological characteristics, when evaluating the effectiveness of current measures to control the total catch for all fisheries.

In the western and central Pacific Ocean, upper strata waters exhibit highly dynamic oceanographic features under ENSO variability. This has been proved to be responsible for the dynamic change of both abundance and zonal distribution of skipjack tuna (Katsuwonus pelamis). Although causality has been suggested by researchers using physical–biological interaction models, cumulative evidence needs to be obtained and the tenability of assertion needs to be tested from an ecological habitat perspective, based on fisheries data. For purse seine fishery, the use of catch per unit effort (CPUE) as an indication of the abundance is confusing because of technical improvements over the whole exploitation history and unbalanced individual fishing characteristic of vessels. It is particularly interesting to discriminate between habitat characteristics in comparative scenarios of CPUE application. This study identified habitat traits based on a series of oceanographic factors from a global ocean reanalysis model. A comparison was conducted between two habitat models based on unprocessed purse seine CPUE and standardized CPUE considering fishing characteristics. The results suggest that standardized CPUE could model the regular zonal shift of habitat compatible with the observed fishing efforts transfer, and achieved better prediction capacity than unprocessed CPUE. Furthermore, the habitat of skipjack tuna was also characterized and linked with surface and subsurface thermal environment, ocean current, dissolved oxygen, biotic environment, and ENSO variability. The monthly-averaged habitat suitable index, derived from the optimal habitat model prediction, showed a significant linear relationship with the southern oscillation index, which suggested that El Niño episodes eventually provide more preferable habitat for skipjack tuna under ENSO variability.

The current lack of high-precision information on subsurface seawater is a constraint in fishery research. Based on Argo temperature and salinity profiles, this study applied the gradient-dependent optimal interpolation to reconstruct daily subsurface oceanic environmental information according to fishery dates and locations. The relationship between subsurface information and matching yellowfin tuna (YFT) in the western and central Pacific Ocean (WCPO) was examined using catch data from January 1, 2008 to August 31, 2017. The seawater temperature and salinity results showed differences of less than ±0.5°C and ±0.01 compared with the truth observations respectively. Statistical analysis revealed that the most suitable temperature for YFT fishery was 28–29°C at the near-surface. The most suitable salinity range for YFT fishery was 34.5–36.0 at depths shallower than 300 m. The suitable upper and lower bounds on the depths of the thermocline were 90–100 m and 300–350 m, respectively. The thermocline characteristics were prominent, with a mean temperature gradient exceeding 0.08°C/m. These results indicate that the profiles constructed by gradient-dependent optimal interpolation were more accurate than those of the nearest profiles adopted.

Theoretically, propagating internal tides in the ocean may reflect at turning depths, where buoyancy frequencies equal tidal frequencies, before colliding with the air-sea interface or rugged bottom topography. Globally, the internal tide lower turning depths (ITLTDs) in the open ocean have been mapped; however, knowledge of the presence of ITLTDs in the South China Sea (SCS) is lacking. In this study, 2 125 high-quality temperature-salinity profiles (including 58 deep-sea hydrographic measurements with observational depths exceeding 3 000 m) are collected and analyzed to investigate the existence of ITLTDs in the SCS. Furthermore, the concept of the upper turning depth is first introduced in the context of internal tides, and internal tide upper turning depths (ITUTDs) are also investigated. ITLTDs are found to exist at several abyssal stations; these stations are distributed mostly in the southern part of the SCS basin, possibly due to the greater water depths there. Fewer locations show the presence of ITLTDs for K₁ versus M₂ tidal frequencies because of the lower tidal frequency. The distance between ITLTDs and the seafloor ranged from 270 m to more than 1 200 m, implying the possible existence of multiple internal wave evanescent regions in the abyssal bottom. ITUTDs of tens of meters are ubiquitous in the SCS; stations with the presence of ITUTDs are located mainly in the northeastern SCS due to the intensive observations there. However, the calculated ITUTDs have large uncertainties; they are sensitive to the selected bin values. The horizontal propagation directions of internal tides in the SCS change dramatically, and as a result, the estimated turning depths under the full Coriolis force definition are different compared to that under the traditional approximation.

A large sand bar develops in the inner Qiantang River Estuary, China. It is a unique sedimentary system, elongating landwards by about 130 km. Based on long-term series of bathymetric data in each April, July, and November since the 1960s, this study investigated the morphological behavior of this bar under natural conditions and the influence of a large-scale river narrowing project (LRNP) implemented in the last decades. The results show that three timescales, namely the seasonal, interannual and decadal timescales, can be distinguished for the sand bar evolution. The first two are related to the seasonal and interannual variations of river discharge. During high discharge seasons or years, erosion took place at the upper reach and sedimentation at the lower reach. Consequently, the bar apex shifted seaward. The opposite development took place during low discharge seasons or years. The decadal timescale is related to LRNP. Due to the implementation of LRNP, the upper reach has experienced apparent erosion and currently a new equilibrium state has been reached; whereas the lower reach has been accumulated seriously and the accumulation still continues. Nonlinear relationships for how the bar apex location and elevation depend on the river discharge over various stages of LRNP have been established. Compared with the earlier stage of LRNP, the bar apex at present has shifted seaward by about 12 km and lowered by about 1 m. The sand bar movement has significant feedback on the hydrographic conditions along the estuary and has practical implications for coastal management.