Effects of environmental enrichment on the welfare of juvenile black rockfish Sebastes schlegelii: Growth, behavior and physiology

Abstract Background Black rockfish (Sebastes schlegelii) is a viviparous teleost. We proposed that the rockfish ovarian wall had a similar function to the uterus of mammals previously. In the present study, the well-developed vascular system was observed in the ovarian wall and the exterior surface of the egg membrane. In gestation, adaptation of the ovary vasculature to the rising needs of the embryos occurs through both vasodilation and neovascularization. Bdkrb2, encoding a receptor for bradykinin, plays a critical role in the control of vasodilatation by regulating nitric oxide production. Results Eight Bdkrb2 genes were identified in the black rockfish genome. These genes were located on chromosome 14, which are arranged in a tandem array, forming a gene cluster spanning 50 kb. Protein structure prediction, phylogenetic analysis, and transcriptome analysis showed that eight Bdkrb2 genes evolved two kinds of protein structure and three types of tissue expression pattern. Overexpression of two Bdkrb2 genes in zebrafish indicated a role of them in blood vessel formation or remodeling, which is an important procedure for the viviparous rockfish getting prepared for fertilization and embryos implantation. Conclusions Our study characterizes eight Bdrkb2 genes in the black rockfish, which may contribute to preparation for fertilization and embryo implantation. This research provides a novel view of viviparity adaptation and lays the groundwork for future research into vascular regulation of ovarian tissue in the breeding cycle in black rockfish.

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Effects of Food Deprivation Duration on the Behavior and Metabolism of Black Rockfish (Sebastes schlegelii)

Fishes ◽

10.3390/fishes6040058 ◽

2021 ◽

Vol 6 (4) ◽

pp. 58

Author(s):

Fengyuan Shen ◽

Zonghang Zhang ◽

Yiqiu Fu ◽

Zhen Zhang ◽

Xin Sun ◽

...

Keyword(s):

Food Deprivation ◽

Personality Assessment ◽

Behavioral Assessment ◽

Standard Metabolic Rate ◽

Control Group ◽

Black Rockfish ◽

Swimming Time ◽

Sebastes Schlegelii ◽

Food Shortages

Fish often undergo food shortages in nature, especially for juveniles that are relatively vulnerable in most aspects. Therefore, the effects of food deprivation on fish behavior and physiology are worth exploring. Here, we investigated the behavioral and metabolic adaptations of the juvenile black rockfish Sebastes schlegelii to different durations of food deprivation. In this study, three treatments were set: control group, short-term food deprivation (STFD) group, and long-term food deprivation (LTFD) group. The rearing lasted for six weeks. During this period, videos were recorded three times per week to assess the locomotor activity and aggression. After this, the fishes’ boldness, neophobia, and aggressiveness were assessed using different behavioral assessment devices, while the standard metabolic rate (SMR) was measured by flow-type respirometry. In general, the values of the four indicators (swimming time, the number of turns, movement number, and attack number) for the STFD group were significantly higher than those for the control and LTFD group during the same period of rearing. In a subsequent personality assessment, the STFD group was observed to be significantly bolder in an assessment measuring boldness than the control and LTFD group (indicated by time in the circle, swimming time, number of times through the circle, and frequency in the circle). The LTFD group was observed to be more exploratory in the assessment of neophobia (indicated by duration in the exploratory area, distance from novelty item, and frequency of stay in the exploratory area). Indeed, the LTFD group was observed to be significantly less aggressive in the assessment of aggressiveness than the control and STFD group (indicated by attack number, attack range frequency, first attack, and winner). SMR was noted to be significantly higher in the STFD group than in the control and LTFD group. In conclusion, this study firstly reported the effects of food deprivation duration on the personalities of black rockfish, as well as the behavioral and physiological mechanisms. Thus, we hope to provide insights into the work of stock enhancement.

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