Genetic Stock Identification and Adaptability of Hatchery-Reared Black Rockfish, Sebastes schlegelii, Released Into the North Yellow Sea waters

Abstract

Successful stock enhancement refers to the maintenance of economic profit, whilst minimizing negative genetic and ecological effects. As hatchery environments differ from natural habitats, post-release identification of hatchery-reared juveniles, and estimation of their adaptability are essential steps in conducting responsible stock enhancement. The black rockfish is an important fishery species in Japan, South Korea and China. Overfishing has dramatically decreased natural resources and a stock enhancement program was first initiated in the Liaodong peninsula in 2019. We traced this program and used nine microsatellite markers to identify 279 individuals as being hatchery-reared, out of 710 captured fish, with a resource contribution rate of 39.30%. These results indicated that stock enhancement of this species is likely to maintain a positive economic performance. To understand the potential genetic impacts on the local wild population, the genetic patterns of S. schlegelii stocks (wild controls from 2017, wild controls from 2018, female broodstock from 2019, recaptured hatchery-reared fish from 2019 and recaptured non-hatchery-reared fish from 2019 stocks) from the same habitat were evaluated before and after artificial stocking. We found that the S. schlegelii population was able to maintain high genetic diversity and showed weak genetic differentiation, but potential genetic introgression derived from stock enhancement should be concerned. The hatchery-reared individuals showed good adaptability, as shown by feeding condition and growth status. There was no obvious morphology difference between hatchery-reared fish and their wild counterparts, but hatchery-reared fish seemed to be bigger in size (significantly higher in MDB and BW), had a larger head (significantly larger in PRL/HL and ID/HL) and smaller paired fins (significantly smaller PCFL/BL), when compared with wild individuals across all investigation months. Our results provided insights into management of black rockfish enhancement in the future.

Population genetics analysis of the black rockfish Sebastes schlegelii in Northern China based on 2b-RAD simplified genome sequencing

“…The Ho (0.174-0.273) was higher than He (0.173-0.234) in seven populations, indicating that the seven populations may be mixed with others and need further purification. Additionally, previous studies have reported the genetic diversity of S. schlegelii used to microsatellite DNA loci, 1,32 that the Ho, He, and PIC was much higher than this study. Recent studies have explored the genetic diversity of the black rockfish from a total of three populations in northern China using mtDNA loop analysis, and the results showed no significant genetic differentiation and low genetic differentiation.…”

“…34 This is considered an adaptive mechanism to alleviate the constraints of limited individual exchange caused by short-distance migrations, which suggests that hatchery-reared fish can maintain a high level of genetic diversity. 1 The Fst and DR are essential parameters to measure the degree of genetic differentiation among populations. 35 In this study, the cultured population CDYZ showed moderate differentiation from the six wild populations, while the six wild populations showed low differentiation.…”

“…It is considered a tasty seafood with high market value and additional recreational value. 1 This fish is distributed along the Northwestern Pacific Ocean, especially in the Yellow Sea, Bohai Sea, the South Sea of Korea, and the coastal areas of Japan. 2 Overfishing has decimated the natural resources of S. schlegelii in recent years, and programs aimed at enhancing fish stock have been initiated.…”

“…The S. schlegelii population maintained high genetic diversity and showed weak genetic differentiation, but potential genetic introgression derived from stock enhancement should be considered. 1 However, no studies assessing the genetic diversity of black rockfish populations are based on genome-wide variation information.…”

Evaluation of the Residency of Black Rockfish (Sebastes schlegelii) in Artificial Reef Areas Based on Stable Carbon Isotopes

“…Considering its relatively shorter body length (67 mm) and consistent δ 13 C value in muscle aligned with the reef area isoscape, it is possible that summer Fish 1 might be a newly born individual within the reef area or could have originated from juvenile individuals released inshore. Notably, in China, between 2015 and 2019, over 30 million black rockfish were released in the Shandong Peninsula in the Bohai and Yellow Seas, driven by rapid growth in the hatchery industry and advances in aquaculture technology [44]. Stock enhancement activities for black rockfish were implemented between June and July, with the body length of released individuals measuring approximately 50 mm [45].…”