History of herring fishery in Hokkaido and the review of population study.

Herring fishery in Hokkaido of northern Japan began in the middle of fifteenth century. At that time gill-net fishery was operated. Since then accompanied with the developing of fishing gears annual catch of herring increased. It reached about 0.15 million tons in 1850s. A historical peak of catch of 0.97 million tons was recorded in 1897. This high level of production was mainly from the Hokkaido-Sakhalin population. However it has steadily declined thereafter and has disappeared since 1955 from Hokkaido coast. Some changes of oceanic environmental conditions have been observed. It has been thought that these factors influenced to the disappearance of the population. Since that time some local populations have been targeted by coastal fishery. Over one million artificial herring fly have been released to enhance the stock size of local populations in recent years.Population study carried out in Japan was reviewed breafly. Author classified nine genetically distinguished populations distributed around northern Japan into following four groups; group I is lagoon small migration type, 2is oceanic wide migration type, group Ⅲ is oceanic small migration type, and group Ⅳ is intermediate type of Ⅰand Ⅱ.

Resource condition of herring populations caught by fisheries in Sakhalin Island waters (Review)

The coasts of Sakhalin are notable for their herring population variety. However, only the Sakhalin-Hokkaido, De-Kastri and northeastern (NE) coast of Sakhalin populations are considered commercially important. Abundance of the De-Kastri and the NE coast of Sakhalin populations are not high compared with the Sakhalin-Hokkaido herring population. Catches of all Sakhalin populations is much lower than Okhotsk, Gizhiginsk-Kamchatsk, or Korfo-Karaginsk in recent years.
Presently, herring of the NE coast of Sakhalin and the De-Kastri are characterized by low abundance. One of the biggest populations in the North Pacific in the past, Sakhalin-Hokkaido herring have been in low abundance for some decades. Drastically decreased abundance is caused both by loss of spawning and feeding areas and changing population age-structure. 

Processing and Use of Herring in Hokkaido (Review)

From 1945 to around 1955, herrings were processed into fertilizer, herring oil, salted herrings, and dried herring roe. However, since the 1970s, when imported herrings began to be used as raw materials, they have been used primarily to produce dried herring fillets, salted herring roe, seasoned herring roe and frozen herrings.
The characteristics of herring products by production center were analyzed and categorized into the following: weight ratio by region, pH, general ingredients, fatty acid composition, free amino acid composition of fish meat and ovaries, ovary maturation and the quality of herring roe, the mechanism of ovary consolidation, and the damage to herring roe sustained during freezing. Moreover, the by-origin suitability of processing of herring was also summarized, based on data from the Hokkaido Federation of Marine Products Processing Cooperative Associations, combined with results of tests carried out by Fisheries Experimental Stations.
In addition, the test results and the technical problems experienced during the processing and use of herring from 1983 to 1996 are described.

Temporal variation in the 20th century of coastal sea temperature and annual herring landings off the west coast of Hokkaido

The present study addresses oceanographic environment relations to changed distribution and reproduction processes shown by Pacific herring, Clupea pallasi, of the Hokkaido-Sakhalin stock. The west coast of Hokkaido in the 20th century is studied using coastal sea temperature as an index of oceanographic environment.
Coastal sea temperatures at nine selected stations at the west coast of Hokkaido are normalized using the period when observations were overlapped for 30 years from 1931 to 1960. Normalized coastal sea temperatures are averaged to construct a time series, in excess of a century, of indexes for monthly, seasonal and annual mean normalized coastal sea temperatures from 1897 to 2000.
The relation between annual catch of herring in the Hiyama division and the coastal sea temperature index during winter season is shown to have strong negative correlation. This result leads to the conclusion that a well known phenomenon, the disappearance of spawning runs beginning in the south and regularly extending northward along the west coast of Hokkaido, is mainly caused by increase in sea water temperature during winter time.
Correlation between monthly mean normalized coastal sea temperature and relative year-class strength of herring calculated from 1907 to 1955 was investigated. From all the periods with significant correlation, the tendency is confirmed: the colder the normalized coastal sea temperature, the more the relative year-class strength of herring. These relations lead to a hypothesis that occurrence frequency of herring strong year-class is represented as a probability function of normalized coastal sea temperature and the frequency increases(decreases) in the negative(positive) direction of this temperature from May to July and from September to November. Characteristic variations for relative year-class strength of herring appear to be well-explained qualitatively by this hypothesis even before and after the period when the hypothesis is derived. Ecosystem structure, for which temperature is one determinant, is understood to influence the herring as a whole system; the frequency of herring strong year-class occurrence increases in years of low coastal sea temperature and that of weak year-class of herring increases in years of high coastal sea temperature.
Results of this study verify that long-term coastal sea temperature changes caused by atmosphere-ocean interaction strongly affect variation of Hokkaido-Sakhalin herring stock.

Recent stock structure of herring (Clupea pallasii ) caught by the coastal fisheries in the mid-northern Japan Sea, Hokkaido, Japan.

Herring (Clupea pallasii ) in the mid-northern Japan Sea of Hokkaido was examined to elucidate stock structure and biological characteristics of herring caught by commercial fisheries. Presently, in the Japan Sea off middle-northern Hokkaido, herring are caught by coastal fisheries and trawl fisheries. Total catch by the coastal fisheries exceeded that by trawl fisheries from 1996 through 1999. In the coastal fisheries, annual catch by gill net comprised over 92% from 1995 through 2000. The catch in the Rirei Area(Rishiri and Rebun Is.) was highest among survey areas from 1991 through 2000. In the Rirei Area, herring were mainly caught from November to February of the following year. The herring population caught in the Rirei Area differed from the Ishikari Bay population. In Hokkaido Areas (from Shiribeshi Area to Soya Area), the herring fishery mainly operated from February to April. The herring population caught in Hokkaido Areas from 1996 through 2000 was mostly Ishikari Bay population. Catch of Ishikari Bay population has increased since 1997. This population spawned in the coastal waters from the Ishikari Bay to the Soya Bay during February to April.

Annual catch fluctuations and size composition of Ishikari Bay herring (Pacific herring,, Clupea pallasi VALENCIENNES) for the last 40 years

To examine stock size fluctuation and factors influencing it, we estimated annual catches since 1962 using fishery statistic data and published reports. Also, yearly size compositions of Ishikari Bay herring spawners caught between 1967-1977 and 1996-2000 were calculated. Annual catches have ranged from 1 (in 1993) to 239 (in 2001) metric tons. Catches have fluctuated on a relatively large scale over a short term in the 1970s, thereafter decreasing to a low level from the 1980s until 1996. In 1997, catches sharply increased; they have remained high at levels over 100 metric tons. Fork length frequency distributions of herring showed mono-modal or bimodal shape, mainly consisted 2-year-old fish (mean fork length 23-25 cm, spawning for first time). This result suggests close association with short time fluctuation of Ishikari Bay herring stock.

Reproductive characteristics of Ishikari Bay herring (Clupea pallasi VALENCIENNES)

Localized Pacific herring, so called "Ishikari Bay herring" exists in waters off western and northern part of Hokkaido, Sea of Japan. Annual catches of herring spawners fluctuated for 1 to 14t in 1980-1996 and have sharply increased to 158-239 metric tons in 1997-2001. Present study is based on an investigation of specimens caught by gill net and Danish seine between November 1997 and April 2001 in Ishikari Bay and adjacent waters. Gonosomatic index and macroscopic ovary appearance suggested that Ishikari Bay herring spawn from early February to early May, mainly late February and March. Large-sized fish (over 27cm in fork-length) become to mature earlier than small-sized fish, so spawning herring caught in early fishing season were larger than those of the late season. Condition factor (CF) decreased in February and/or March at minimum level. There was positive correlation between egg size and fork-length of mature spawning herring. The relationship between fecundity (E) and fork-length (FL in cm) were shown with a regression of E=0.760 FL3.344 (r=0.939).
These results are important for understanding stock fluctuation and conducting fisheries management.

Natural spawning beds of herring in the Rumoi district along the coast of northwestern Hokkaido from 1998 to 2001.

The natural spawning beds of herring (Clupea pallasii Valenciennes) were investigated along the Rumoi coast, Hokkaido, Japan from 1996 to 2001. Seven spawning beds were found at seaweed beds shallower than 2m deep from 1998 to 2001. Milky white turbidity of sea surface due to herring spawning was observed in three times (Reuke in 1999, 2001 and Onishika in 2001). Estimated total number of eggs were ranging from 84.5×106 to 263.1×106, average egg density was ranging from 10,834 to 571,000/㎡, and maximum egg density was ranging from 176×103 to 2.5×106/㎡. The species of seaweeds attached with the large number of eggs were Phyllospadix iwatensis, Sargassum confusum, and Coccophora langsdorfii. Daily average of water temperature in the spawning periods were ranging from 2.8 to 4.7℃. Salinity of the spawning beds in these periods were diluted and fluctuated due to melting snow. On the spawning days it was calm with the character of low wave height, low wave velocity, easterly wind, and cloudy sky. The spawning schools of herring would be considered to come through the ditches on the sea floors from offshore to the spawning beds.

Effect of vegetation and topography on the spawning bed selection of herring, Clupea pallasii.

Pacific herring (Clupea pallasii) spawn in Atsuta, on the west coast of Hokkaido, northern Japan, was surveyed by divers in 1998 and 1999. Some grooves existed on the flat rocky shore developed at Minedomari, Atsuta. Spawning beds of herring were located near the grooves year by year. Herring used sea grass, Phyllospadix iwatensis, as spawning substratum. Maximum egg density was 101,375 per small quadrate (0.25m×0.25m) in 1998. Sea grass biomass affected egg density. Sea grass biomass, leaf density and number of eggs per sea grass biomass unit were significantly higher within grooves outside of them. These surveys showed that egg distribution is dependent on the sea grass density and the groove existence on the rocky shore available for use as a passage to enter the shallower area at Minedomari, Atsuta.

Water temperature and salinity in the spawning bed of herring (Clupea pallasii), and estimating of spawnig period based on the water temperature.

Water temperature and salinity in herring spawning beds on the rocky shore were surveyed at Minedomari, Atsuta, Hokkaido during the 2000 spawning season. Water temperature was 4℃ during mid-March spawning and 7-8℃ at the mid-April hatch. Average temperature was 5.2℃ in the spawning bed and 4.7℃ at deeper bottom off Minedomari. Cumulative temperature from spawn to hatch was 138.8℃ in the spawning bed. This value was almost equal to the 136℃ obtained in the laboratory where eggs were kept under 8.5 ℃. Spawning period in field could be estimated based on cumulative temperature for respective developmental stages and water temperatures. Salinity changed very widely from 7psu to over 30psu after the end of March due to melting snow. Spawning on the shallower rocky shore at Atsuta adapted to reduce the incubation period through higher temperature and obtain good conditions for development and hatch outthrough adequate salinity.

Occurrence of juvenile herring Clupea pallasi around Sohya Bay, northern Hokkaido, Japan.

Juveniles of Pacific herring Clupea pallasi, caught by anglers at fishing ports and harbors located around Sohya Bay during June to November in 1999-2000, were studied. Specimens consisted of 1-age and 0-age in either year and the latter contained some hatchery-reared fry ALC-marked and released under the stock enhancement program carried out by Hokkaido Government. The 0-age juveniles were thought to be derived from local population in northwestern coast of Hokkaido formerly known as Ishikari Herring characterized with relatively higher vertebral counts. In contrast, the origin of 1-age juveniles was not clear because of smaller number of specimens and rather common vertebral features among populations known around Hokkaido, though their vertebrae were counted lower than 0-age juveniles. Body length frequency of 0-age juveniles exhibited bimodal distributions and suggested two groups of juveniles possibly originated from different spawning date or grounds in those studied area. Change of recapture sites indicated the trend of northword movement of released-reared fry for a few months after liberty. Released-reared fry caught within a month after liberty exhbited apparently poor condition factor, and it is suggested that remarkable increase of their mean body length was not caused by remarkable growth but selective removal of smaller fry.

Validation of daily increments in the otolith microstructure of Ishikari Bay herring larvae.

Daily increment formation was verified in the laboratory by comparing the number of increments between alizarin complexion (ALC) marking on 19th and 33rd day after hatching. The number of increments between two marks with ALC corresponded with the number of days elapsed between the first and the second ALC treatments with a small standard deviation. These results indicate that rate of increment formation was 1-day from at least 19 days after hatching. However, the deposition rate estimated from the relationship between the actual number of days after hatching and the number of increment counted was close to one, but significantly different from one increment per day.
The standard deviation of the estimated age from the real age was very high, which is in accordance with previous study on Pacific herring and Atlantic herring. A possible explanation for the large standard deviation of the estimated age from the real age (±3 days) in the Ishikari Bay herring is the individual differences in the day first increment, which is visible under light microscope, is formed. Consequently an error of 3 days or so for the estimation of the number of days after hatching of Ishikari Bay herring under light microscope is considered being unavoidable.

The intermediate culture of the artificially produced juvenile of the Pacific herring, Clupea pallasii in Ishikari Bay, Hokkaido.

The examination was performed about the growth and the survival rate of the artificially produced juvenile Pacific herring by intermediate culture from 1996 to 2000, at Ishikari bay in West Coast in Hokkaido. The total length of these artificial herrings distributed from Hokkaido Aquaculture Haboro Center is 42.3-51.2 mm, and grew up to 60.8-69.5 mm in the fish pens of the intermediate culture in Atsuta and Hamamasu. These periods of intermediate culture was 19-28 days, and the survival rate of these periods was 96.1-98.8%. The mean of the growth per day in these periods was 0.75mm/day. The relation of the growth per day and daily age were straight lines-like. The artificial feed given to the herrings in these periods was 2.1 to 8.7 kg/day, and it was 1.9-8.7% of the body weight of herrings, and correlation was not accepted between the amount of feeds of this range, and growth of the herrings. The rate in which a herring less than 50mm, 50-52mm and 52mm or more passes through 5mm meshes was 25-100%,10-30% and 4% or less respectively .In the area where a net tends to become dirty, the growth of the herring raised with the 5mm mesh's fish pens was better than the herring raised with the 3mm mesh's fish pens .

Ecology of artificially produced juvenile herring（Clupea pallasii）released in Ishikari Bay-I
Distribution and migration within about a month after release

To examine the suitable body size, timing and placement at release of artificial produced juvenile herring, we investigated thedistribution and migration within a month after the releases on released seeds sampled with fishing, a beach seine, larva net, and a small beam trawl at the coast of Atsuta Village, and with set nets in the Ishikari River in summer, from 1996 to 1999.
Within a week after release artificial produced herring were collected around release area. Afterward, artificial produced herring moved northward from release point; they moved to the Ishikari River estuary southward from release point from late June to middle July. Finaly, they moved to Atsuta northward from the release point from mid- July to late July. Size distributions in total length of recaptured fish became larger as time passed each year, collection of artificial produced fish more than 90 mm was very rare.
These results indicate that released artificial produced fish dispersed around release area untill early July after their release. From then they moved northward and a portion of them moved southward after release; to late June, they dispersed at the Ishikari　River estuary and sand vicinity of the Ishikari　River, leaving the coastal area left coastal area when they grew to about 90 mm total length.

Ecology of artificial produced juvenile herring (Clupea pallasii) released at Ishikari Bay- II　Feeding habits within about a month after release.

To examine the suitable body size, timing and placement of release for artificial produced juvenile herring，we investigated the distribution and feeding habits of sampled artificial produced juvenile herring collected using a beach seine, larvae net, a small beam trawl and fishing at the coast of Atsuta and with set nets in the Ishikari River on the west coast of Hokkaido in Japan， in summer, 1996 - 1999.
Artificial produced herring fed on various food organisms in one day after releasing and fed on a large number on 8 days and 11 days after release. However the composition of food organisms differed between sampling locations and dates, the majority of food organisms of juveniles up to 70mm in total length comprised larvae of fish and a number of small coastal and brackish copepods (i.e. Oithona atlantica and Eurytemora spp.), and cladocerans (i.e. Moina sp. and Podon spp.), oikopleura. Artificial produced herring greater than 80 mm mainly fed on larger organisms such as mysidacea, amphipoda, and fish larvae.

Result of pilot experiment　of starvation resistance of　 artificially　produced Pacific herring （Clupea pallasii）

The starvation　resistance of Pacific herring （Clupea pallasii）was studied in rearing experiments　with two fish groups; mean total length of fish used in experiments were 47㎜ (range: 36.5-58.0mm) and 68㎜(range: 64.0-75 mm) . After starvation, 50% mortality the 47mm and the 68mm size groups occurred by days 19 day and 27, respectively.　The relationship between days fish died with starvation(D) and total length (L: mm) is represented by the formula D＝0.70×L－19.5.
A few of 47 mm size group fed at 11 days after the beginning　of starvation experiment died immediately after feeding again; subsequently, others survived and the relation　between total length and weight removed the alimentary canal, lever, and heart came to be as same fed fish.　Some of 68 mm size group fish, fed at 21 days after the beginning　of starvation experiment also died within　a couple of days after feeding commenced again but others survived and relation　between total length and the weight came to be the same as fed fish.
The ratio of weight between fish　under normal conditions　and　died are 0.87 on 40 mm, 0.76 on 60 mm, 0.70 on 80 mm, respectively. From these experimental results clarifying the feeding habits of　released artificial produced herring and the feeding ability of herring juvenile, we conclude that released fish do not often die directly from starvation.

Growth and maturation of hatchery-reared Hokkaido-Sakhalin herring population, Clupea pallasii

Growth and maturation of artificially reared Hokkaido-Sakhalin herring population, Clupea pallasii were examined for two years after hatching. During the rearing period from September 1998 to May 2000 water temperature was in the range of 2.1-15.7℃(mean 8.8℃). At the age of one year, average total length and body weight were 153.2±9.5mm and 26.0±6.5g respectively ; at two years, they were 232.2±19.3mm and 107.8±25.9g. The growth curve described by von Bertalanffy equation is Lt=293.629[1-exp{-0.76815(t+0.046)}], where Lt is the total length (cm) of fish at age t(years after hatching). The relationship between total length and body weight is described by the equation W=0.0049L3.1731 where L is total length (cm) and W is body weight (g). The daily growth rate decreased with increasing body size from 2.79% at 185 days after hatching to 0.04% at 615 days. Maturation was first observed at the age of two years; the maturation rate was 10.6%. Average fertilization rates by artificial egg collection and hatching were 93.1±6.8% and 65.9±29.6%, respectively.

Short-term recapture of hatchery-reared herring released at Wakkanai coast,northern Hokkaido in 2001(Short paper)

Estimating hatching day distribution in Ishikari Bay herring larvae and juveniles from daily growth increments in otolith.(Short paper)

Estimated hatching day sampled at St. A on 11 Jun. showed a bimodal shape peaked in early Apl. (early-hatched larvae and juveniles) and early May (late-hatched larvae and juveniles). At St. B on 24 Jun., early-hatched juveniles were dominated, but most of juveniles sampled on 2 Jul. and 8 Jul. were late-hatched. At St. C on 3 Jul., early-hatched juveniles were dominant although late-hatched juveniles were at St. B in this period. On 13 Jul. at St. C showed a bimodal shape; first and second peaks were similar to that on 11 Jun., indicating that the early-hatched individuals migrated earlier to the surf area (St. B) and the estuary, than the late hatched ones.
Migration of adult herring for spawning to the coastal Atsuta peaked twice, early Feb. and late Feb. in 1999. Results of direct research by SCUBA diving for in situ observations of herring eggs at Atsuta showed that hatching peaked on 9-10 Apl. and 5-6 May in 1999. These results indicated that larvae and juveniles used in this study originated from the eggs spawned around Atsuta.

Suitable body sites and tissue for implanting binary coded wire tag (CWT)in juvenile hatchery-reared harring(Short paper)