日本海でホタルイカやイワシの大群が押し寄せています。
先日、富山県でホタルイカが豊漁というニュースが報じられていました。統計の残る１９５３年以降、３月としては最も多い１１５３トンに上ったことを県水産研究所（滑川市）が報告していました。３月の漁獲量は平年（過去１０年間の平均）の３８１トンの３倍に上り、これまで最も多かった１１１９トン（９２年）を超えました。ホタルイカは例年、３月下旬から５月下旬に漁獲量のピークを迎え、今後も豊漁が見込まれています。近年、ホタルイカは不漁だっただけに、富山県は盛り上がっているようです。
一方、北海道では季節外れのイワシの大群が押し寄せているようです。北海道留萌市（るもいし）では、これまで見られなかったイワシの大群が港を埋め尽くしています。多くの人がイワシを釣り上げ、イワシ料理を堪能しているようです。また北海道厚真町では、大量の北寄貝が海岸に打ち上げられ、多くの住人が拾いに来ています。北寄貝は１年中水揚げされるのですが、冬から初春の寒い時期が美味しい季節です。冬季の冷たい海水で身が引き締まっていることと、産卵期を前に栄養が蓄えられていることで、特に肉厚で味が良いとされています。北寄貝は水深１０ｍほどの海底の砂地で身を潜め、長い水管を延ばして水を吸い、そこに含まれるプランクトンを食べます。水深１０ｍ程度なら、打ち上げられても不思議ではないでしょう。
近年、異常な豊漁が多くほじられています。
イワシの豊漁は昨年も報じられていました。また、昨年冬のブリの豊漁も耳に新しいニュースです。魚介類は水温や海流により回遊経路が大きく変わるので、近年の水温上昇が影響しているとされています。水温上昇により磯焼けが日本全国で発生しています。その結果、関サバ・関アジなど、日本の南方で獲れる近海魚の漁獲高が激減しています。異常な豊漁は報じられますが、不漁はあまり報じられません。九州地方では魚の養殖も行われているので、水温上昇の影響が出るかもしれません。
海の中の変化は分かりにくいので、水中ドローンでの海中観察が有効です。
海水温上昇は深刻な環境問題ですが、あまり大きく注目されていません。特に近海は水深が浅いため、海水温上昇は大きな影響を与えます。海岸に行ってみると、本来、冬から春にかけて岸壁に海藻が生い茂っています。しかし、今の岸壁には貝殻のみが付着しています。また、春になると植物プランクトンが大量発生して、海水の透明度が下がります。しかし現在、海岸の海水は透明度が中の高く、まるで冬の海の様です。
海水温上昇による海の変化は、魚介類の生息域を大きく移動させています。その結果、多くの港で多くの魚種が不漁となっています。継続的な不漁により、漁師が漁に出なくなり、漁師を辞める人も続出しています。このままでは、日本の漁業が危機となるでしょう。海の中を観察して、魚の生息域や行動範囲を調査する必要があります。魚群探知機と水中ドローンを用いた海中調査は、定置網の設置などに有効と考えられています。当社では水中ドローンのレンタルを行っております。是非、ご活用ください。
#ホタルイカ #イワシ #豊漁 #北寄貝
Large schools of firefly squid and sardines are flooding the Sea of Japan.
The other day, there was news reporting that there was a good catch of firefly squid in Toyama Prefecture. The Prefectural Fisheries Research Institute (Namekawa City) reported that the amount reached 1,153 tons, the highest amount for March since 1953, when statistics are still available. The catch in March was three times the normal year (average for the past 10 years) of 381 tons, and exceeded the previous record of 1,119 tons (1992). The catch of firefly squid usually reaches its peak from late March to late May, and a good catch is expected to continue in the future. In recent years, firefly squid fishing has been poor, but Toyama Prefecture seems to be enjoying a boom.
Meanwhile, it seems that large schools of sardines are swarming out of season in Hokkaido. In Rumoi City, Hokkaido, schools of sardines that have never been seen before are filling the port. Many people seem to be fishing for sardines and enjoying sardine dishes. In addition, in Atsuma Town, Hokkaido, a large number of northern shellfish are washed up on the shore, and many residents come to pick them up. Kitayori shellfish are caught all year round, but the best time to catch them is during the cold months from winter to early spring. The meat is said to be especially thick and delicious because its flesh is firm due to the cold seawater in the winter, and because it has stored nutrients before the spawning season. The northern shellfish hides in the sandy bottom of the ocean at a depth of about 10 meters, extends long water tubes to suck in water, and eats the plankton contained therein. If the water is about 10m deep, it wouldn't be surprising if it were washed ashore.
In recent years, many unusually rich catches have been harvested.
A good catch of sardines was reported last year as well. Also, the good catch of yellowtail last winter is new news. Seafood migration routes change significantly depending on water temperature and ocean currents, so it is believed that the recent rise in water temperature has had an effect. Rocky shores are occurring across Japan due to rising water temperatures. As a result, the catch of inshore fish caught in the southern part of Japan, such as Seki mackerel and Seki horse mackerel, has drastically decreased. Abnormally rich catches are reported, but poor catches are rarely reported. Fish farming is also carried out in the Kyushu region, so there may be an impact from rising water temperatures.
It is difficult to understand changes in the ocean, so underwater observation using an underwater drone is effective.
Rising seawater temperatures are a serious environmental problem, but they have not received much attention. Rising seawater temperatures will have a major impact, especially in coastal waters, where the water is shallow. When you go to the coast, you will find seaweed growing on the quay from winter to spring. However, only shells are attached to the quay today. Additionally, in spring, phytoplankton blooms in large numbers, reducing the clarity of seawater. However, the seawater on the coast is now medium-transparent, resembling a winter sea.
Changes in the ocean caused by rising seawater temperatures are causing large shifts in the habitats of fish and shellfish. As a result, many fish species are not being caught in many ports. Due to continued poor catches, many fishermen are no longer going fishing, and many are quitting their jobs. If things continue like this, Japan's fishing industry will be in crisis. It is necessary to observe the ocean and investigate the habitat and movement range of fish. Underwater surveys using fish finders and underwater drones are considered effective for setting up fixed nets. We rent underwater drones. Please take advantage of it.
#FireflySquid #Sardines #BigCatch #KitayoriShellfish
