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Global plastic production has surged since the 1960s, resulting in the pervasive presence of microplastics in the environment, yet there is a substantial gap in understanding historical trends of plastic pollution in wildlife. Recent discoveries of significant microplastic contamination in fishes have sparked considerable contemporary advancements in analytical methods and hold the potential to fill gaps in historical trends. We measured the presence of microplastics in museum-archived myctophids (Stenobrachius leucopsarus, Diaphus theta, and Tarletonbeania crenularis) collected from 1962 to 2016, to determine if trends in contamination levels over time correspond with the rise in plastics production. Seventy particles were extracted from 57 of the 240 individuals (23.8 % average occurrence across the time series) consisting of primarily blue and black microfibers. Anthropogenically modified cellulose was the dominant material (87 %) identified through μFTIR analysis, with polypropylene and polyethylene particles occurring secondarily. Although the complete time series across a broad geographical range of the North Pacific did not reveal a significant temporal trend, myctophids collected in proximity to the U.S. west coast showed a trend towards increasing incidence of microplastic and microfiber ingestion over time (p ≤ 0.05). Using historical samples of species with higher ingestion levels and consistent collection locations would improve the reliability of future investigations., Competing Interests: Declaration of competing interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a conflict of interest., (Published by Elsevier B.V.)

Dispersal of eggs and larvae from spawning sites is critical to the population dynamics and conservation of marine fishes. For overfished species like critically endangered Nassau grouper ( Epinephelus striatus ), recovery depends on the fate of eggs spawned at the few remaining aggregation sites. Biophysical models can predict larval dispersal, yet these rely on assumed values of key parameters, such as diffusion and mortality rates, which have historically been difficult or impossible to estimate. We used in situ imaging to record three-dimensional positions of individual eggs and larvae in proximity to oceanographic drifters released into egg plumes from the largest known Nassau grouper spawning aggregation. We then estimated a diffusion-mortality model and applied it to previous years' drifter tracks to evaluate the possibility of retention versus export to nearby sites within 5 days of spawning. Results indicate that larvae were retained locally in 2011 and 2017, with 2011 recruitment being a substantial driver of population recovery on Little Cayman. Export to a nearby island with a depleted population occurred in 2016. After two decades of protection, the population appears to be self-replenishing but also capable of seeding recruitment in the region, supporting calls to incorporate spawning aggregation protections into fisheries management.

Thiamine (vitamin B 1 ) metabolism is an important driver of human and animal health and ecological functioning. Some organisms, including species of ferns, mollusks, and fish, contain thiamine-degrading enzymes known as thiaminases, and consumption of these organisms can lead to thiamine deficiency in the consumer. Consumption of fish containing thiaminase has led to elevated mortality and recruitment failure in farmed animals and wild salmonine populations around the world. In the North American Great Lakes, consumption of the non-native prey fish alewife (Alosa pseudoharengus) by native lake trout (Salvelinus namaycush) led to thiamine deficiency in the trout, contributed to elevated fry mortality, and impeded natural population recruitment. Several thiaminases have been genetically characterized in bacteria and unicellular eukaryotes, and the source of thiaminase in multicellular organisms has been hypothesized to be gut microflora. In an unexpected discovery, we identified thiaminase I genes in zebrafish (Danio rerio) with homology to bacterial tenA thiaminase II. The biochemical activity of zebrafish thiaminase I (GenBank NP_001314821.1) was confirmed in a recombinant system. Genes homologous to the zebrafish tenA-like thiaminase I were identified in many animals, including common carp (Cyprinus carpio), zebra mussel (Dreissena polymorpha) and alewife. Thus, the source of thiaminase I in alewife impacting lake trout populations is likely to be de novo synthesis., (© 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Passive acoustic monitoring of ocean soundscapes can provide information on ecosystem status for those tasked with protecting marine resources. In 2015, the National Oceanic and Atmospheric Administration (NOAA) established a long-term, continuous, low-frequency (10 Hz-2 kHz) passive acoustic monitoring site in the Cordell Bank National Marine Sanctuary (CBNMS), located offshore of the central United States of America (U.S.) west coast, near San Francisco, CA. The California Current flows southward along the coast in this area, supporting a diverse community of marine animals, including several baleen whale species. Acoustic data analysis revealed that both large vessels and vocalizing baleen whales contribute to the ambient soundscape of the CBNMS. Sound levels fluctuated by month with the highest levels in the fall and lowest levels in the summer. Throughout the year, very low-frequency (10-100 Hz) sound levels were most variable. Vessels and whales overlap in their contributions to ambient sound levels within this range, although vessel contributions were more omnipresent, while seasonal peaks were associated with vocalizing whales. This characterization of low-frequency ambient sound levels in the CBNMS establishes initial baselines for an important component of this site's underwater soundscape. Standardized monitoring of soundscapes directly supports NOAA's ability to evaluate and report on conditions within national marine sanctuaries.

Many large-bodied marine fishes that form spawning aggregations, such as the Nassau grouper ( Epinephelus striatus ), have suffered regional overfishing due to exploitation during spawning. In response, marine resource managers in many locations have established marine protected areas or seasonal closures to recover these overfished stocks. The challenge in assessing management effectiveness lies largely in the development of accurate estimates to track stock size through time. For the past 15 y, the Cayman Islands government has taken a series of management actions aimed at recovering collapsed stocks of Nassau grouper. Importantly, the government also partnered with academic and nonprofit organizations to establish a research and monitoring program (Grouper Moon) aimed at documenting the impacts of conservation action. Here, we develop an integrated population model of 2 Cayman Nassau grouper stocks based on both diver-collected mark-resight observations and video censuses. Using both data types across multiple years, we fit parameters for a state-space model for population growth. We show that over the last 15 y the Nassau grouper population on Little Cayman has more than tripled in response to conservation efforts. Census data from Cayman Brac, while more sparse, show a similar pattern. These findings demonstrate that spatial and seasonal closures aimed at rebuilding aggregation-based fisheries can foster conservation success., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

Despite evidence of maternal age effects in a number of teleost species, there have been challenges to the assertion that maternal age intrinsically influences offspring quality. From an evolutionary perspective, maternal age effects result in young females paradoxically investing in less fit offspring despite a greater potential fitness benefit that might be gained by allocating this energy to individual somatic growth. Although a narrow range of conditions could lead to a maternal fitness benefit via the production of lower quality offspring, evolutionary theorists suggest these conditions are seldom met and that the reported maternal age effects are more likely products of the environmental context. Our goal was to determine if maternal effects operated on offspring provisioning in a long-lived rockfish (genus Sebastes ), and to evaluate any such effects as an intrinsic function of maternal age or a context-dependent effect of the offspring release environment. We found that offspring provisioning is a function of both maternal age and the timing of offspring release; older females exhibit increased provisioning over younger females throughout the spawning season despite a decrease in provisioning across all maternal ages as the season progresses. These findings suggest a role for both maternal age effects and a potential context-dependent maternal effect in population productivity, carrying important implications when modelling population persistence and resilience., Competing Interests: We have no competing interests.

To address patterns of genetic connectivity in a mass-aggregating marine fish, we analyzed genetic variation in mitochondrial DNA (mtDNA), microsatellites, and single nucleotide polymorphisms (SNPs) for Nassau grouper (Epinephelus striatus). We expected Nassau grouper to exhibit genetic differentiation among its subpopulations due to its reproductive behavior and retentive oceanographic conditions experienced across the Caribbean basin. All samples were genotyped for two mitochondrial markers and 9 microsatellite loci, and a subset of samples were genotyped for 4,234 SNPs. We found evidence of genetic differentiation in a Caribbean-wide study of this mass-aggregating marine fish using mtDNA (FST = 0.206, p<0.001), microsatellites (FST = 0.002, p = 0.004) and SNPs (FST = 0.002, p = 0.014), and identified three potential barriers to larval dispersal. Genetically isolated regions identified in our work mirror those seen for other invertebrate and fish species in the Caribbean basin. Oceanographic regimes in the Caribbean may largely explain patterns of genetic differentiation among Nassau grouper subpopulations. Regional patterns observed warrant standardization of fisheries management and conservation initiatives among countries within genetically isolated regions.

Spatial coherence between predators and prey has rarely been observed in pelagic marine ecosystems. We used measures of the environment, prey abundance, prey quality, and prey distribution to explain the observed distributions of three co-occurring predator species breeding on islands in the southeastern Bering Sea: black-legged kittiwakes (Rissa tridactyla), thick-billed murres (Uria lomvia), and northern fur seals (Callorhinus ursinus). Predictions of statistical models were tested using movement patterns obtained from satellite-tracked individual animals. With the most commonly used measures to quantify prey distributions--areal biomass, density, and numerical abundance--we were unable to find a spatial relationship between predators and their prey. We instead found that habitat use by all three predators was predicted most strongly by prey patch characteristics such as depth and local density within spatial aggregations. Additional prey patch characteristics and physical habitat also contributed significantly to characterizing predator patterns. Our results indicate that the small-scale prey patch characteristics are critical to how predators perceive the quality of their food supply and the mechanisms they use to exploit it, regardless of time of day, sampling year, or source colony. The three focal predator species had different constraints and employed different foraging strategies--a shallow diver that makes trips of moderate distance (kittiwakes), a deep diver that makes trip of short distances (murres), and a deep diver that makes extensive trips (fur seals). However, all three were similarly linked by patchiness of prey rather than by the distribution of overall biomass. This supports the hypothesis that patchiness may be critical for understanding predator-prey relationships in pelagic marine systems more generally.

Populations of gag (Mycteroperca microlepis), a hermaphroditic grouper, have experienced a dramatic shift in sex ratio over the past 25 years due to a decline in older age classes. The highly female-skewed sex ratio can be predicted as a consequence of increased fishing mortality that truncates the age distribution, and raises some concern about the overall fitness of the population. Management efforts may need to be directed toward maintenance of sex ratio as well as stock size, with evaluations of recruitment based on sex ratio or male stock size in addition to the traditional female-based stock-recruitment relationship. We used two stochastic, age-structured models to heuristically compare the effects of reducing fishing mortality on different life history stages and the relative impact of reductions in fertilization rates that may occur with highly skewed sex ratios. Our response variables included population size, sex ratio, lost egg fertility, and female spawning stock biomass. Population growth rates were highest for scenarios that reduced mortality for female gag (nearshore closure), while improved sex ratios were obtained most quickly with spawning reserves. The effect of reduced fertility through sex ratio bias was generally low but depended on the management scenario employed. Our results demonstrate the utility of evaluation of fishery management scenarios through model analysis and simulation, the synergistic interaction of life history and response to changes in mortality rates, and the importance of defining management goals.

Androgens are known to play many roles in the reproductive physiology of teleosts, but less information exists on the role that they play in the development of larval and juvenile fish. This study examines an observed seasonal cycle of 11-ketotestosterone (11KT) in females of the hermaphroditic gag grouper (Mycteroperca microlepis). Otoliths, gonads, and plasma samples from gag were collected quarterly (spring, summer, fall, and winter), with complete data (age, sex, and androgen levels) obtained from a total of 225 individuals. Ages ranged from zero to 11 years, and all individuals were female. Testosterone (T) peaked in the spring, coincident with spawning, and was low throughout the remainder of the year. The androgen 11KT peaked in summer and declined through the following spring. 11KT levels were negatively correlated with fish size in both the summer and winter, while T was negatively correlated in the summer and positively correlated in the winter. T levels showed little seasonal variation in juveniles (0-1 and 2-3 age groups), but showed a seasonal increase from fall through spring in older fish (4-5 and 6+ age groups). Age 0-1 fish had significantly higher levels of 11KT than the age 4-5 group during the summer and both the 4-5 and 6+ age groups in the winter. The gag is a protogynous hermaphrodite that goes through several ontogenetic shifts during its life, and this seasonal fluctuation in plasma levels of 11KT may play a role in the growth and development, behavior, or control of sex change of gag.

The egg yolk precursor protein, vitellogenin (VTG), was purified from blood plasma of 17beta-estradiol (E2)-treated male fathead minnows (Pimephales promnelas) by anion-exchange chromatography on DEAE-agarose. A rabbit antiserum was raised against their blood plasma and then adsorbed with plasma from untreated (control) males to render the antiserum specific to VTG. The adsorbed antiserum was used to detect fathead minnow VTG (fVTG) in Western and dot blotting experiments and in an enzyme-linked immunosorbent assay (ELISA). The antiserum recognised fVTG as a approximately 156 kDa protein in plasma from vitellogenic females and E2-injected males but not untreated males. Its identity was confirmed by analysis of: (1) amino acid composition; (2) an internal amino acid sequence; (3) reactivity to the homologous antiserum; and (4) recognition by monoclonal antibodies prepared against the VTG from common carp (Cyprinus carpio) and brown bullhead (Ameiurus nebulosus). Specificity of the homologous antiserum to fVTG was confirmed by Western blotting of serially diluted plasma from vitellogenic females. Utility of the antiserum and purified fVTG for detecting exposure of male fathead minnows to estrogenic compounds was verified using a dot blotting immunoassay of fVTG and detected by chemiluminescence. Adult male fish were exposed to various concentrations of E2 (10(-8), 10(-9) and 10(-10) M) in their rearing water and plasma assayed for the presence of VTG at different time points (2, 7, 14 and 21 days). A competitive, antibody-capture, quantitative ELISA was then developed based on the purified fVTG and its respective antiserum. The ELISA was validated by demonstrating parallel binding slopes of dilution curves prepared with plasma from E2-injected males, vitellogenic females, and aqueous egg extracts as compared with purified fVTG standard. Plasma concentrations of VTG as low as 3 ng ml(-1) were detected in the ELISA, for which inter- and intra-assay coefficients of variation were both less than 5%. Furthermore, plasma from control males was unreactive with the fVTG antiserum. The VTG ELISA could be useful for the detection of estrogenic properties associated with certain compounds and could be easily incorporated into standard laboratory toxicity assays using this species.

Vitellogenin (VTG), the serum phospholipoglycoprotein precursor to egg yolk, is potentially an ideal biomarker for environmental estrogens. This study was undertaken to develop antibodies against conserved regions on the VTG molecule that could form the basis for establishing bioassays to detect estrogen exposure in any oviparous vertebrate. We developed monoclonal antibodies (mAbs) generated against purified rainbow trout (Oncorhynchus mykiss) VTG and selected for the property of specifically recognizing VTG purified from two phylogenetically distant vertebrates, trout and striped bass (Morone saxatilis). Results of enzyme-linked immunosorbent assay and Western blotting indicated that these mAbs specifically recognize purified VTG and VTG or other estrogen-inducible proteins in plasma or serum from representative species of four vertebrate classes (fish, amphibians, reptiles, and birds). All of the mAbs generated were IgM class. A polyclonal antiserum was raised against a synthetic consensus peptide representing the conserved N-terminal amino acid sequence of VTG. The results of Western blotting indicate that this antiserum specifically recognizes VTG in plasma or serum from teleost fish of diverse families. It was used to detect VTG in Western blots of serum from brown bullhead (Ameiurus nebulosus) with cancer (hepatocellular and cholangio-carcinoma) collected from a contaminated industrial site outside of their normal vitellogenic season. Our results indicate that it is feasible to generate antibodies capable of recognizing VTG without regard to species and that development of a universal VTG assay is an achievable goal.