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SUMMARY:This paper estimates the age and growth of the alfonsino Beryx splendens in the waters around the Izu Islands off the Pacific side of Japan. The samples consist of 250 fish of the landings of the offshore longliners from December 1995 to November 1996 and 10 fish of the coastal longliners in February of 1995. By the surface method using a microscope, a reader counted the number of hyaline and opaque zones on the sagittal otoliths, judged whether the edge was hyaline, and measured the radii from the focus to the outer edge of each hyaline zone. In order to estimate the parameters of the von Bertalanffy’s growth equation representing the overall ages, the age and fork length data and the mean length at 1 year old. In a previous study were used for the maximum likelihood approach. From the results, the rate of readability of the otolith from the offshore samples was 97.6% and that from the coastal samples was 100%. The monthly changes in the frequency of the opaque edge showed that the hyaline and opaque zones were laid down once a year. The hyaline zone began to form from May to July (peaking in August). The ages of the offshore samples for both the sexes ranged from 2 to 23 years, and those of the coastal samples 2 to 5, respectively. The estimated growth curves were expressed by l(t) = 44.4[1–exp{–0.132(t + 3.45)}] for males and l(t) = 45.0[1–exp{–0.150(t + 2.08)}] for females, where l(t) and t denote the fork length (cm) and the age in years, respectively. The issues to be resolved in the future were discussed. [ABSTRACT FROM AUTHOR]

We examined specimens from the winter–spring cohort of the neon flying squid Ommastrephes bartramii caught off the coast of northeastern Japan in early summer and the following winter for mantle length, sex, maturity, and age to determine their hatching dates as well as their growth and migration patterns. Squid specimens were collected with a research driftnet in July 2018 in the northwestern Pacific and by squid jigging off the coast of northeastern Japan in November 2018 and January 2019. The ages of 300 specimens were estimated from statolith increment counts and used to back-calculate hatching dates. Hatching dates ranged from September 2017 to July 2018. The peak hatching dates varied with the survey season, even for the same winter–spring cohort. Squid caught in July 2018 hatched mainly from February to April, while those caught in November 2018 hatched mostly during April and May and those caught in January 2019 hatched principally during May and June. This pattern indicates that squid migrate among fishing grounds and that stocks are gradually replaced by late-hatching squid. [ABSTRACT FROM AUTHOR]

The effects of temperature and prey density on the recent growth rate (RGR) of chub mackerel, Scomber japonicus, were examined. Scomber spp. larvae and juveniles were collected along the Boso–Kashimanada Pacific coast in Japan between March and July in 2015 and 2016. Larvae and juveniles identified as S. japonicus using DNA were subjected to stomach-content and otolith-increment analyses. The effects of temperature and prey density on RGR were analyzed using a generalized linear mixed model (GLMM), which showed that temperature positively affected the RGR of larvae in the body length (BL) classes < 5 mm, 5–7 mm, 7–9 mm and 9–11 mm. Prey density also affected growth in the < 5 mm, 5–7 mm, 7–9 mm and > 11 mm classes and effects of prey density on RGR for larger (> 11 mm) larvae and juveniles were stronger than those for smaller (< 9 mm) larvae. S. japonicus larvae transform into juveniles at around 12 mm BL, and the increased feed demands of juveniles likely lead to prey-density-dependent growth. The otolith increment widths of larvae and juveniles were significantly narrower than those during the same stages in 1-year-old S. japonicus collected from purse seine fisheries operated in the Joban or Kashimanada areas, suggesting growth-dependent mortality. [ABSTRACT FROM AUTHOR]

Habitat utilization, feeding, and growth of a rare pleuronectid flatfish, spotted halibut Verasper variegatus, were examined in a brackish lagoon in northeastern Japan: Matsukawa-ura. The distribution and date-length data of spotted halibut collected mainly from beam-trawl samplings during 1983-2008 indicated that age-0 juveniles [ n = 25, 6.0-18.0 cm total length (TL)] and older spotted halibut ( n = 71, 13.8-43.0 cm TL) inhabited almost the entire northern part of Matsukawa-ura. Comparative distribution surveys of spotted halibut, stone flounder, and marbled flounder during 1985-1989 revealed similar distribution patterns of these flatfishes; the highest densities were found around the central part of Matsukawa-ura, although significantly lower abundance was detected for spotted halibut. Linear growth equations of age-0 juveniles demonstrated that spotted halibut were able to achieve high growth after June, probably because abundant prey (e.g., mysids and gammarids) and suitable physical conditions (warmer water temperature and lower salinity) were present. The main prey items shifted from various crustaceans including mysids, caridean shrimps, and anomurans to brachyura Hemigrapsus spp. (≥20 cm TL). Our study shows that spotted halibut use the shallow brackish lagoon as an important nursery for juveniles, and also as a feeding ground for young and adults. [ABSTRACT FROM AUTHOR]

We examined individual growth and fatness in the 1975-2002 year classes of Japanese sardine. Samples were collected at the feeding grounds in the Pacific waters off northern Japan during drastic fluctuations in the population in the 1970s to 2000s. Growth rates for ages 1-3 of the 1979-1988 year classes, which included low-recruitment year classes subsisting during the high population levels of the 1980s, were apparently slower than for other year classes. There was no obvious trend when comparing year classes, growth during the first year of life (age 0), and maximum body length (BL) at age ≥5. The condition factors (CF, indicating fatness) for adult sardines of BL ≥19 cm in the 1979-1983 year classes during the maximum population level of the mid-1980s were significantly lower than for other year classes. However, there were no apparent trends in CF variations for small sardines of BL <19 cm. The apparent decreases in growth rate and fatness were strongly related to the cumulative sum of population abundance that each year class experienced. It is thought that insufficient food owing to the density-dependent effect of an abundant population at feeding grounds resulted in a decrease in the growth rate for small-bodied sardines that are investing their energy intake in body growth, and a decrease in fatness for large-bodied adults that are accumulating fat for the next reproduction. [ABSTRACT FROM AUTHOR]

The optimal water temperature in seed germination and the upper critical water temperature in seedling growth were determined for Zostera japonica collected from Ago Bay, Japan. The relationship between the seed germination rates and seed storage period (0, 30, and 60 days) at 0°C was also examined. The optimal water temperature in seed germination was in the range 15–20°C regardless of the storage period, in which germination rates were up to 14%. Seedlings, grown from seeds up to 10 cm in total length, were cultured for 1 week at various water temperatures to measure their relative growth rates. The optimal water temperature in early growth was in the range 20–25°C; relative growth rates ranged from 3.8 to 4.2%. Seedlings could survive up to a water temperature of 29°C, but most seedlings withered at 30 or 35°C. The optimal water temperatures for seed germination and seedling growth were related to the seasonal changes of water temperature in the sampling site. Although seedlings were hardly observed in Ago Bay in summer, Z. japonica might extend its distribution as far as where the summer water temperature is lower than 29°C. [ABSTRACT FROM AUTHOR]

The optimal water temperature in seed germination and the upper critical water temperature in seedling growth were determined for Zostera marina collected from Ise Bay, Japan. The relationship between the seed germination rates and seed storage period (0, 30 and 60 days at 0°C) was also examined. The optimal water temperature for seed germination was in the range from 10 to 15°C regardless of the storage periods, in which germination rates ranged from 35 to 57%. Seedlings grown from seed up to 10 cm in total length were cultured for 1 week under various water temperatures to measure their relative growth rates. The optimal water temperature in growth was in the range from 20 to 25°C; relative growth rates ranged from 2.0 to 2.6%. Seedlings could survive up to a water temperature of 28°C, but most seedlings withered at 29 or 30°C. The optimal water temperatures for seed germination and seedling growth were related to the seasonal changes of water temperature at the sampling site. Although seedlings were rarely observed in the field in summer, they can grow at temperatures as high as 28°C. Therefore, Z. marina may extend its distribution as far as where the summer water temperature is lower than 28°C. [ABSTRACT FROM AUTHOR]

The biomass of bighand thornyhead Sebastolobus macrochir was increased by the high recruitment success of the 1999–2002 year classes off the Pacific coast of northern Honshu, Japan. In this study, the growth of bighand thornyhead was examined over a 9-year period from 1996 to 2004 in this area. The growth of the 1999 year class and the 2000–2002 year classes was reduced at 3 and 2 years old, respectively, while the 1999–2002 year classes were smaller than the 1993–1998 year classes. In 2-, 3- and 4-year-old fish, the relationship between abundance and mean standard length was expressed by negative linear regressions, while fish became smaller when abundance of the year class was larger. Mean bottom temperatures were stable at depths of 350–900 m; variations in water temperature were small in the main distribution area of bighand thornyhead. We discuss the factors affecting the growth of bighand thornyhead via changes in the demersal fish community and feeding habits. [ABSTRACT FROM AUTHOR]

The fourspine sculpin Cottus kazika is indigenous to Japan and found in Honshu except for the waters facing the Seto Inland Sea, and was also found in southern Shikoku and eastern Kyushu. This species has a catadromous lifestyle and migrates as juveniles from the sea to the middle reaches of rivers to grow. The growth pattern of this fish was investigated by a mark-and-recapture method from July 1994 to December 1996, in the Nigorikawa River, a tributary of the Gonokawa River system, Shimane Prefecture. 0-year-old fish of 50–70 mm total length ( TL) occurred in the study area from June to July, grew to 90–140 mm TL by the following April, and attained 160–210 mm TL by December. This fish grew rapidly in September–November and April–July, almost ceasing to grow in July–September. It seems that this stagnant growth phase in summer is a characteristic of the seasonal growth pattern of C. kazika. A rearing experiment indicated that the growth rate of C. kazika was higher at 16–22°C than at 12–14 and 24–26°C. This result supports the field evidence of a stagnant growth phase in summer in the Nigorikawa River. [ABSTRACT FROM AUTHOR]

To study the mechanism of faster growth of the sculpin Cottus kazika in seawater (SW) than in fresh water (FW), we transferred 120-day-old juveniles from FW to SW, 1/3 SW or FW, and survival, growth and levels of transcripts of growth hormone (GH) gene in the pituitary and insulin-like growth factor I (IGF-I) gene in the liver were examined 20 and 40 days after transfer. The survival rates of fish reared in SW and 1/3 SW were higher than the FW controls. The growth was fastest in SW and slowest in the controls. IGF-I gene transcripts increased in SW-reared fish 40 days after transfer compared with the controls, while GH gene transcripts did not. Juveniles of 1 year of age were transferred from FW to SW or 1/3 SW, and GH and IGF-I gene transcripts were compared after 48 h. In this short-term experiment, the level of GH gene transcripts was higher in fish reared in SW and 1/3 SW, while no difference was found in the IGF-I gene transcripts. Thus, the GH gene transcripts increased only transiently after SW transfer but the IGF-I gene transcripts increased gradually for 40 days, suggesting that the long-term increase in IGF-I gene expression is involved in the enhanced growth in SW and GH may play an initiation role for growth enhancement. [ABSTRACT FROM AUTHOR]

Age and growth of the yellowstriped butterfish,Labracoglossa argentiventris, around Izu Oshima Island were studied using a total of 1450 fish. Age was determined by counting the edge of the opaque zones as a ring mark on sectioned sagittal otoliths. Formation of the first ring was observed during spring or summer, corresponding to 1.5 years after hatching. Thereafter, one ring was formed each year in the same season as the previous year. The growth of the butterfish was rapid until 2 years of age. The maximum likelihood method was applied to the age and length data for estimating parameters in von Bertalanffy, Gompertz, and Logistic growth models. The selected model, based on the Akaike Information Criterion, was the von Bertalanffy growth model, which indicated differential asymptotic length and variance by sex. [ABSTRACT FROM AUTHOR]

The blackspot snapperLutjanus fulviflammusis one of the most commonLutjanusspecies landed and consumed on Okinawa Island, Japan. Using 901 fish (29.9–304.2 mm in standard length; SL) obtained from fish markets or caught by angling, the age, growth, maturation size and maturation age were estimated. Each opaque zone formed on the otolith every year correlated with their spawning and was thought to be an annual ring. The main spawning season was estimated to be from April to July, which peaked in May and June, with a few mature fish collected in August and September. Maximum ages were observed as 24 years for both sexes and L∞ (mm SL), K and t0 (years) of the von Bertalanffy growth formula were estimated to be 276, 0.144 and−5.22 for females and 247, 0.227 and−3.18 for males, respectively. First maturation size and age were estimated to be 175 mm SL and 2 years for both sexes. A faster growth rate up to 2 years will allow reproduction at a young age and provide many chances for spawning throughout their long life. Furthermore, the possibility exists that populations would easily recover if regulations were established. [ABSTRACT FROM AUTHOR]

Age and growth of alfonsinoBeryx splendens(Lowe) were studied using counts of presumed daily incremental growth rings on the transverse section of otoliths of fish collected from the Kanto District, central Japan. Microstructural growth increments were observed from the core to the outermost margin of the broadest of approximately 50 branches formed on the surface of an otolith. Of 98 otoliths examined, 46 were readable. The number of increments and fish lengths ranged from 448 (218 mm fork length[FL]) to 3701 (411 mm FL). The ages of these fish were estimated to be 1 year, 2 months and 10 years, 2 months, respectively, assuming that an increment was formed daily. The von Bertalanffy growth equation combined for males and females was expressed as follows:L t = 542{1 − exp [−0.133(t + 2.00)]}, whereL t is fork length (mm) at yearly aget. The results of the present study were compared with those of other researchers who had studied alfonsino from central Japan. [ABSTRACT FROM AUTHOR]

Effects of hypoxia on the principal prey and growth of flathead flounder Hippoglossoides dubius were studied in Funka Bay. Of the three dominant year-classes that occurred in recent years, the 1995 year-class was small in total length at age ≥ 3 and low in condition factor at age ≥ 2. Ophiuroids (almost Ophiura sarsi), which were the dominant prey in the 1980s, were of little importance and instead, crustaceans such as mysids, natant decapods and pelagic amphipods, bivalves and fish were important prey items for H. dubius in 2000–2001. In addition, the feeding intensity of H. dubius in 2000–2001 was lower than that in the 1980s. These facts are closely related to a reduction of prey abundance, particularly ophiuroids. It seems that the hypoxia that occurred in the central part of the bay during the summer and autumn of 1995–1997 caused the poor food supply and low growth rate at ages 2–4 of the 1995 year-class. [ABSTRACT FROM AUTHOR]

Changes in the growth of the Japanese sardine Sardinops melanostictus during a period of declining stock size was examined by using sardines sampled from 1990 to 1996 in Tosa Bay, south-western Japan, one of the main spawning grounds on the Pacific coast of Japan during February and March. The growth parameter k -values of the von Bertalanffy growth equation of female sardines were small in the 1987–1990 years classes, while the values for the 1991–1992 years classes were larger, which corresponded closely with the decrease in catch of the sardines in south-western Japan, suggesting that there are density-dependent effects on the growth of sardines in Tosa Bay. In contrast, the body length decreased since the 1993 years class, but the fatness of female sardines improved after 1993. Since 1994, many I year females with transparent eggs in the ovaries have been collected from Tosa Bay. It is speculated that good nutritional conditions of the 1993 year class led to maturation at an earlier age, and that the decrease of growth from the 1993 year class occurred due to the reduction of resources channeled to growth as a result of the maturation at I year. [ABSTRACT FROM AUTHOR]

Life history parameters (growth pattern, the length of the spawningseason and age at sexual maturity) of Apogon lineatus wereinvestigated from three localities in Japan. The maximum ages werefound to be 3 years in Tokyo Bay, 2 years in Osaka Bay and 5 yearsoff Niigata Prefecture. Both sexes from Tokyo Bay grew to largersizes between the ages of 1 and 2 years than both sexes from otherlocalities, food availability being suggested as the major factorfor differences in growth. Spawning seasons were during 4 months(July–October) in Tokyo Bay and Osaka Bay, but were foundto only occur during the two months of July and August off NiigataPrefecture. Factors that could limit the spawning season off NiigataPrefecture were not determined. Age at maturity for both sexes inall localities appeared to be 1 year. We could not elucidate whetherthese variations in life history parameters arose from genetic differencesor from phenotypic plasticity. In either case, the trade-off betweenthe maximum age and the length of the spawning season in the offNiigata Prefecture population and any other population may be interpretedas an adaptation to local conditions, such as with the off NiigataPrefecture population. [ABSTRACT FROM AUTHOR]

Growth and reproduction of hatchery-reared Chinese white prawn Penaeus chinensis released in the Ariake Sea, Japan, were examined. Chinese white prawn grew rapidly, reaching a body length of 154 mm in males and 198 mm in females by November (219--229 days after hatch-ing). Maximum body length of sampled individuals was 164 mm in males and 223 mm in females. Growth curve of the Chinese white prawn was fitted to the Pitcher and MacDonalds formula, Lt =155.0{1 -e 2.925sin[2 (t -16.151)/365] -0.0623(t -10.712) for males and the logistic curve, Lt =200.3/[1 + e (1.9850.034t) ] for females (where Lt is the body length t days after release and t is the number of days after release). Females reached sexual maturity in late February and spawning occurred until April. Minimum size at ripe and spawned stages was 189 mm and 193 mm body length, respectively. [ABSTRACT FROM AUTHOR]

SUMMARY:A total of 325 pueruli of the spiny lobster Panulirus japonicus was successfully reared in the laboratory at Minami-Iku Station of Japan Sea-Farming Association, Shizuoka, Japan, during 1989–1997. Of these pueruli, 136 individuals metamorphosed into the first juvenile stage. The duration of the phyllosoma stage ranged from 231 to 417 days (mean 319.4 days), and it has a tendency to extend as the increase of water volume in the rearing tanks. The number of molting in the phyllosoma stage was 20–31. The body length of the last-stage phyllosoma ranged from 27.9 to 34.2 mm and the duration of the last stage was 11–26 days. The carapace length of the puerulus stage was 6.0–8.0 mm and the duration was 9–26 days. The present data and those of previous studies suggest that the body size and the duration of phyllosoma stage in captivity are affected by environment as in the field. The duration of the puerulus stage is considered to be controlled basically by water temperature and nutritional conditions in the phyllosoma. [ABSTRACT FROM AUTHOR]

Discusses the effect of an artificial diet on early spat growth of the Japanese pearl oyster Pinctada fucata martensii. Artificial breeding of pearl oyster; Preparation of gelatin-acacia microcapsules; Production of pearl oyster spat.

Examines the effect of seasonal changes on the quantitative and qualitative composition of carbohydrate in vegetative shoots of eelgrass Zostera marina at Odawa Bay in Kanagawa, Japan. Increase in photosynthetic production; Translocation of the produced sugar from the leaves to the rhizomes; Relation between sugar level and solar radiation.