Effects of Stocking Density on Stress, Hematological Responses, and Growth of Black Rockfish Sebastes schlegelii

Abstract

The objective of the current study was to evaluate the effect of stocking density on juvenile Black Rockfish Sebastes schlegelii (average weight = 12 g) in terms of stress, hematological responses, and growth performance during a 4‐month growth trial in a flow‐through system. The initial stocking densities were 1.3 kg/m3 (low), 1.8 kg/m3 (medium), and 2.3 kg/m3 (high), and the final densities were 4.9 kg/m3 (low), 5.6 kg/m3 (medium), and 6.3 kg/m3 (high). At the end of the trial, the high stocking density significantly affected growth characteristics, levels of growth hormone and insulin‐like growth factor 1, and hematological indices (hematocrit, red blood cell count, and hemoglobin level) compared to the medium and low stocking densities. The plasma cortisol and immunoglobulin‐M levels were significantly higher at the high density than at the other two densities. Taken together, while the low and medium stocking densities (final densities of up to 5.6 kg/m3) did not affect stress and hematological indices or growth, the high stocking density (final density of 6.3 kg/m3) significantly impacted those variables, which suggests an allostatic load at that density. Thus, the use of a final stocking density less than 6.3 kg/m3 should be considered to avoid compromising the stress and health condition and growth of Black Rockfish at this size and temperature range.

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

“…Second, developing tailored spatial-specific fishing strategies that account for both residency and potential sources of black rockfish contributes significantly to local fishery sustainability. Owing to the limited space and food availability in the reef areas, a high assemblage of individuals can lead to intraspecific competition for refuge and food resources [59,60]. By considering the diverse potential sources of black rockfish, implementing a spatial-specific fishing strategy with distinct quotas can help alleviate intraspecific competition within the reef area and foster a sustainable level of exploitation in coastal regions [61].…”

Impacts of Temperature on the Growth, Feed Utilization, Stress, and Hemato-Immune Responses of Cherry Salmon (Oncorhynchus masou)

“…During the 8-week growth trial, the juvenile salmon were fed a commercial trout diet (protein 51%, lipid 12%, ash 9%, and fiber 3%) twice a day (09:00 and 17:00) at a rate of 1.5% of their BW. Then, 30 min after feeding, the uneaten pellets were collected and counted to determine the feed intake and feed conversion ratio (FCR; Lee et al [44]). Water quality was maintained as described in Table 1.…”

“…From three individuals among the euthanized fish at each sampling time, blood was collected from the caudal vein using a syringe and heparinized tubes (lithium heparin tube, BD, Franklin Lakes, NJ, USA) [45]. Then, a part of the whole blood was used to determine the Hct, RBC count, and Hb concentration of the blood as previously described [45], and the mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) were calculated as described in Section 2.3 [44]. Next, the plasma was separated from the rest of the blood after centrifugation at 13,000× g and 4 • C (Centrifuge Smart R17 Plus, Hanil Scientific Inc., Gimpo, Korea) for 15 min, and it was stored at −80 • C for later use.…”

“…The following formulae were used to calculate the growth parameters, FCR, and daily individual feed intake [44]: where SGR is the specific growth rate, %WG is the percentage weight increase per day, CF is the condition factor, HSI is the Hepatosomatic index, Hct is the hematocrit, and Hb is hemoglobin.…”

“…The plasma cortisol concentration was individually determined (9 fish per treatment) using an enzyme-linked immunosorbent assay (ELISA) kit (Fish Cortisol ELISA kit, CUS-ABIO, Houston, TX, USA) as previously described [44]. Briefly, a competitive (inhibition) reaction between the pre-coated cortisol on the bottom of the well in a 96-well plate and the cortisol in plasma samples and the standard was used to quantify cortisol in the plasma samples using a calibration (standard) curve.…”