Isolation and Structural Determination of Two Novel Phlorotannins from the Brown Alga Ecklonia kurome Okamura,and Their Radical Scavenging Activities

Two novel phlorotannins with a molecular weight of 974, temporarily named 974-A and 974-B, were isolated from the polyphenol powder prepared from the edible marine brown alga Ecklonia kurome Okamura, and their chemical structures were determined by spectroscopic method. The isolated yield of the total of 974-A and 974-B was approximately 4% (w/w) from the polyphenol powder. In 974-A, the carbon at the C2′ position in the A ring of phlorofucofuroeckol-A forms a C–C bond with the carbon at the C2″ position of the C ring of triphloretol-B, while in 974-B, phlorofucofuroeckol-B and triphloretol-B form a C–C bond in the same manner as in 974-A. These structures were supported by high resolution-MS/MS data. To evaluate the antioxidant activities, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and intracellular radical scavenging assay, using 2′,7′-dichlorofluorescin diacetate (DCFH-DA), were performed for 974-A, 974-B, and four known phlorotannins. The results of the DPPH assay showed that the IC₅₀ values of 974-A, 974-B, phlorofucofuroeckol-A, and dieckol were significantly smaller than those of phlorofucofuroeckol-B, phloroglucinol, α-tocopherol, and ascorbic acid. Furthermore, the DCFH-DA assay suggested that 974-A, 974-B, and dieckol reduce intracellular reactive oxygen species most strongly among the tested compounds.     

Stock size fluctuations in chub mackerel (Scomber japonicus) in the East China Sea and the Japan/East Sea

The stock size of chub mackerel (Scomber japonicus) in the East China Sea and the Japan/East Sea has shown a continuous decrease, with fluctuations, from 1975 to 1990. After a remarkable increase in 1992–96, the stock size fell to its lowest level in 1997–99. The spawning success (number of recruits/spawning biomass) fluctuates periodically with a period of several years, although there are no clear relationships between the spawning biomass and the number of recruits. Spawning success was inversely correlated with sea surface temperature (SST). On the contrary, the catch amount and the catch per unit effort (CPUE) of spotted mackerel (Scomber australasicus) has increased since 1997.     

Control of light condition affects the feeding regime and enables successful eye migration in Atlantic halibut juveniles

Incomplete eye migration is one of the major problems in intensive production of juvenile Atlantic halibut. More than 60% of an average juvenile population reared according to best practice suffers from this abnormality. In commercial production, these fish are discharged and represent a substantial economic loss and a large welfare problem. In the present investigation it is demonstrated that by controlling diurnal light and darkness periods together with a meal based feeding regime, incomplete eye migration can be dramatically reduced in production systems for Atlantic halibut.Control groups were reared under continuous light conditions, whereas the experimental groups were given 7 h of darkness and 17 h of light during a 24 hour cycle, in a period lasting from 12 to 35 days post first-feeding. Otherwise both groups were reared under continuous light conditions. All larvae were fed short time enriched Artemia supplied two times daily.The experimental conditions did not affect the overall growth or survival up to day 85 after first feeding. However, 27 ± 3% of the fry reared under continuous light conditions had complete eye migration, whereas in juveniles reared under shifting light and darkness conditions, complete eye migration was 85 ± 7%. These results represent a major improvement in production systems for Atlantic halibut juveniles.     

Linking environmental drivers,juvenile growth,and recruitment for Japanese jack mackerel Trachurus japonicus in the Sea of Japan

Growth traits of juvenile Japanese jack mackerel (Trachurus japonicus) were estimated based on otolith daily increments in spring during 2011–2016 in the southwestern part of the Sea of Japan (SWSJ). Spatial variability in growth traits was examined between the western and eastern areas of the study area. Back-calculated body length at 50 days post hatch varied among areas and years between 26 and 40 mm. Body lengths at age in the eastern area were significantly smaller than those in the western area. Slower growth rate in the eastern area was associated with the lower ambient temperature in the eastern area than in the western area. In the eastern area, interannual variations in the instantaneous growth rate positively correlated with ambient temperature. Furthermore, interannual variations in back-calculated body length during the late larval and early juvenile stages positively correlated with the juvenile abundance. These results suggest that the thermal conditions in the eastern area are indicative of the growth rate and abundance of juvenile T. japonicus in SWSJ. We further examined relationships between juvenile abundance and thermal conditions during 2003–2019 using archived data of this survey and found that the ambient temperature in the eastern area positively correlated with the juvenile abundance and also the strength of the Tsushima Warm Current. Thus, higher temperatures derived from the Tsushima Warm Current result in a faster growth rate during the late larval and early juvenile stages and subsequently higher abundance of T. japonicus juveniles in SWSJ.     

Age, growth and reproductive characteristics of round scad Decapterus maruadsi in the waters off west Kyushu, the east China Sea

ABSTRACT:   The purpose of this study was to determine the growth and reproductive characteristics of round scad Decapterus maruadsi in the East China Sea. The characteristics regarding growth and reproduction of round scad based on otolith reading and gonad histology, respectively, were estimated. The von Bertalanffy's growth model for round scad was estimated as follows:
FL _t  = 342[1 − exp{−0.55( t  + 0.58)}], (1 <  t  < 7)
where FL _t is fork length (mm) at age in years t . The maturation stage of the ovary was observed by histological techniques. June was the main spawning period; the maturation and migratory nucleus stage of the oocyte was observed when the gonad somatic index value was approximately greater than 4.     

Latitudinally distinct stocks of Atlantic cod face fundamentally different biophysical challenges under on-going climate change

The reproductive success of marine ectotherms is especially vulnerable in warming oceans due to alterations in adult physiology, as well as embryonic and larval survival prospects. These vital responses may, however, differ considerably across the species' geographical distribution. Here we investigated the life history, focusing on reproductive ecology, of three spatially distant populations (stocks) of Atlantic cod (Gadus morhua, Gadidae) (50–80° N), in the Irish/Celtic Seas-English Channel Complex, North and Barents Seas, under past and projected climate. First, experimental tracking of spawning behaviour evidenced that the ovulation cycle is highly distressed at ≥9.6 (±0.25)°C (T_up). This knife-edge threshold resulted in erratic spawning frequencies, whereas vitellogenin sequestration remained unaffected, indicating endocrine rather than aerobic scope constraints. Cod in the Celtic Sea-English Channel are, therefore, expected to show critical stock depensation over the next decades as spawning grounds warm above T_up, with Irish Sea cod subsequently at risk. Second, in the relatively cooler North Sea, the northward retraction of Calanus finmarchicus (Calanidae) and Para-Pseudocalanus spp. (Clausocalanidae) (1958–2017) limit cod larvae feeding opportunities, particularly in the southernmost subarea. However, the contrasting increase in Calanus helgolandicus (Calanidae) does not counteract this negative effect, likely because cod larvae hatch ahead of its abundance peaks. Overfishing again comes as a twin effect. Third, in the still relatively cold Barents Sea, the sustainably harvested cod benefit from improved food conditions in the recent ice-free polar region but at the energetic cost of lengthier and faster spawning migrations. Consequently, under climate change local stocks are stressed by different mechanistic factors of varying management severity.     

Control of Neofabraea alba by plant volatile compounds and hot water

Fumigation by plant volatile compounds and hot water treatment were tested in vitro and in vivo for their activity against Neofabraea alba (anamorph Phlyctema vagabunda), the cause of lenticel rot in apple fruit. In vitro trials with volatile compounds showed a consistent inhibition of pathogen growth by carvacrol, trans-cinnamaldehyde, citral and trans-2-hexenal, while (?)-carvone, hexanal, p-anisaldehyde, 2-nonanone and eugenol showed progressively lower inhibition. The greatest inhibition of mycelial growth was demonstrated by carvacrol (effective doses for 50 and 95 inhibition [ED₅₀ and ED₉₅] = 5.9 and 17.0 μL L^?1, respectively; minimum inhibitory concentration [MIC] = 36.9 μL L^?1) and of conidial germination by trans-2-hexenal (ED₅₀ and ED₉₅ = 4.1 and 6.9 μL L^?1, respectively; MIC = 9.2 μL L^?1). Hot water showed a complete inhibition of conidial germination in vitro after 10, 2 and 1 min of exposure at 40, 45 and 50 °C, respectively, and a complete inhibition of mycelial growth after 20 min of exposure at 75 °C. Among the volatile compounds tested, only 25 μL L^?1 of carvacrol slightly reduced fungal infection on artificially infected apples (11.4% efficacy). Hot water treatment at 45 °C for 10 min showed high efficacy in the control of lenticel rot on apples. Reduction of infection was 80% in artificially inoculated fruit (cv Golden Delicious) and 90% in naturally infected fruit (cv Pink Lady) after 90 and 135 d of storage, respectively.