Using environmental DNA methods to improve detectability in an endangered sturgeon (Acipenser sinensis) monitoring program

Background To determine the presence and abundance of an aquatic species in large waterbodies, especially when populations are at low densities, is highly challenging for conservation biologists. Environmental DNA (eDNA) has the potential to offer a noninvasive and cost-effective method to complement traditional population monitoring, however, eDNA has not been extensively applied to study large migratory species. Chinese sturgeon (Acipenser sinensis), is the largest anadromous migratory fish in the Yangtze River, China, and in recent years its population has dramatically declined and spawning has failed, bringing this species to the brink of extinction. In this study, we aim to test the detectability of eDNA methods to determine the presence and relative abundance of reproductive stock of the species and whether eDNA can be used as a tool to reflect behavioral patterns. Chinese sturgeon eDNA was collected from four sites along the spawning ground across an eight month period, to investigate the temporal and spatial distribution using droplet digital PCR (ddPCR). Results We designed a pair of specific primers for Chinese sturgeon and demonstrated the high sensitivity of ddPCR to detect and quantify the Chinese sturgeon eDNA concentration with the limit of detection 0.17 copies/μl, with Chinese sturgeon eDNA been intermittently detected at all sampling sites. There was a consistent temporal pattern among four of the sampling sites that could reflect the movement characteristics of the Chinese sturgeon in the spawning ground, but without a spatial pattern. The eDNA concentration declined by approximately 2–3 × between December 2018 and December 2019. Conclusions The results prove the efficacy of eDNA for monitoring reproductive stock of the Chinese sturgeon and the e decreased eDNA concentration reflect that Chinese sturgeon may survive with an extremely small number of reproductive stock in the Yangtze River. Accordingly, we suggest future conservation measures should focus on both habitat restoration and matured fish restocking to ensure successful spawning. Overall, this study provides encouraging support for the application of eDNA methods to monitor endangered aquatic species.

Godzilla (1998) as camp de-extinction narrative

Godzilla is one of the most famous de-extinct monsters in global popular cinema. Fan loyalty to the original Toho Studios conception of the creature as a super-powered, dinosaur-like creature helps explain the negative response to Roland Emmerich’s 1998 Hollywood version, which re-imagines Godzilla as a giant, irradiated twentieth-century iguana. Emmerich’s film is plotted around the monster’s attempt to use subterranean New York City as a spawning ground. The creature lays eggs that later hatch into baby Godzillas that look suspiciously like Jurassic Park-style velociraptors. Indeed, the movie plays like an expanded version of the last twenty minutes of The Lost World: Jurassic Park (1997): a dinosaur-like creature runs amok in a major American city and is eventually defeated by a plan involving its offspring. Emmerich’s Godzilla is famous for being ‘Godzilla in name only’, yet its extensive intertextuality with The Lost World foregrounds de-extinction themes and imagery. Furthermore, Godzilla (1998) emphasises human action - in this case, 1950s French nuclear tests in French Polynesia - as the cause of the mutant creature’s emergence. Humans causing de-extinction is a key feature of the entire Godzilla franchise and of similar creature features from the 1950s to the present. Akin to its 1950s predecessors, Godzilla’s light, intentionally (and sometimes unintentionally) comedic tone open it to camp readings of the kind analysed by Bridgitte Barclay, who writes that the narrative and aesthetic shortcomings of schlocky sf B movies ‘disengage the audience from the filmic world and expose the mechanics of storytelling, making the master narrative a story and thereby resisting it by showing it as such’. Godzilla does just that, deflating its own anthropocentrism and rampant pro-militarism via its blatantly derivative story, shoddy digital effects and ham-handed dialogue.

Struktur Komunitas Padang Lamun Di Perairan Gili Air, Lombok Utara

Seagrass is a coastal ecosystem that has important role as a feeding ground, a spawning ground and a nursery ground for various marine biota. This study aims to examine the biodiversity of seagrass at Gili Air, North Lombok Regency, West Nusa Tenggara. This study was conducted to observe the cover percentage of seagrass, it's composition, the number of seagrass stands, canopy's height, frequency of seagrass presence, and index of importance of seagrass. Seagrass data was collected using a 50cm x 50cm quadrant transect, with a total area of 100 m2, referring to the monitoring standards set by SeagrassNet. Water quality analysis was carried out at the Bioecology Laboratory of the Aquaculture Study Program, University of Mataram, and at the Laboratory of the Marine Aquaculture Center (BPBL) of Sekotong, West Lombok. The results showed that the seagrass communities in Gili Air waters were composed of 5 (five) species: Halophila ovalis, Thalassia hemperichii, Cymodocea rotundata, Halodulea pinifolia, and Halodule uninervis, with the percentage of coverage ranging from 26.88-39.17%, and the average coverage by 31.53%. Thalassia hemperichii is the species that has the highest contribution to the seagrass community at Gili Air.

Optimization of the flow conditions in the spawning ground of the Chinese sturgeon (Acipenser sinensis) through Gezhouba Dam generating units

Chinese sturgeon (Acipenser sinensis) is a critically endangered species, and waters downstream from Gezhouba Dam are the only known spawning ground. To optimize the velocity conditions in the spawning ground by controlling the opening mode of Gezhouba Dam generator units, a mathematical model of Chinese sturgeon spawning ground was established in FLOW-3D. The model was evaluated with velocity measurements, and the results were determined to be in good agreement. By inverting the 2016–2019 field monitoring results, the model shows that the preferred velocity range for Chinese sturgeon spawning is 0.6–1.5 m/s. Velocity fields of different opening modes of the generator units were simulated with identical discharge. The suitable-velocity area was maximal when all units of Dajiang Plant of Gezhouba Dam were open. For discharges below 12,000 m3/s, most of the area was suitable; for discharges above 12,000 m3/s, the suitable area rapidly decreased with increasing discharge. A comparison of suitable areas under high-flow showed that at discharges of 12,000–15,000 m3/s, opening 11–13 units on the left side was optimal. For discharges above 15,000 m3/s, all units should be open. We used these results to recommend a new operation scheme to support the conservation of Chinese sturgeon.

Response to Environmental Factors of Spawning Ground in the Pearl River Estuary, China

Spawning grounds are important areas for fish survival and reproduction, and play a key role in the supplement of fishery resources. This study investigated environmental effects on the spatiotemporal variability of spawning ground in the Pearl River Estuary (PRE), China, using the generalized additive model (GAM), based on satellite remote sensing (sea surface temperature (SST), chlorophyll-a concentration (Chl-a), sea surface salinity (SSS), depth), and in situ observations. Results showed that 39.8% of the total variation in fish egg density was explained by these factors. Among them, the most important factor was SST, accounting for 14.3%, followed by Depth, SSS, and Chl-a, with contributions of 9.7%, 8.5%, and 7.3%, respectively. Spawning grounds in the PRE were mainly distributed in the waters with SST of 22 °C, depth of 30–50 m, SSS of 16–35 ‰, and Chl-a of 6–15 mg/m3. From spring to summer, the spawning ground moved from the outlet of the PRE to the east. The distribution of the spawning ground in the PRE was mainly affected by the Pearl River Plume (PRP), Guangdong Coastal Current (GCC), and monsoons in this area.

Influence of Spawning Ground Dynamics on the Long-Term Abundance of Japanese Flying Squid (Todarodes pacificus) Winter Cohort

Japanese flying squid (Todarodes pacificus) is one of the most commercially important resources in the Pacific Ocean and its abundance is largely affected by environmental conditions. We examined the influence of environmental factors in potential spawning grounds of the winter cohort, approximated from Japanese and South Korean catch and catch per unit effort (CPUE) data of Japanese flying squid. Annual spawning ground dynamics were constructed using sea surface temperature (SST), submarine elevation and mean Kuroshio axis data from 1979 to 2018. Based on these information, we generated a suite of spawning ground indices including suitability SST-weighted area of potential spawning ground (SSWA), mean values (January–April) of suitable SST (MVSS), and the meridional position (MP) of SST isolines (18–24°C). Comparable interannual-decadal variability patterns were detected between the squid abundance and spawning ground indices, with abrupt shifts around 1990/1991 and in recent decades. In particular, the Pacific Decadal Oscillation is negatively correlated with spawning ground indices, suggesting its role in regulating the environmental dynamics in the area. Further, the gradient forest model underpinned the importance of SSWA, SSWA_Lag1 and MVSS_Lag1 on squid abundance. The CPUE is also shown to be a better abundance index than the annual catch in modeling the species’ response to environmental variability in its spawning grounds. Our findings suggest that it is imperative to pay more and timely attention to the relationship between the abundance of Japanese flying squid and environmental changes, especially under adverse environmental conditions.