Annual catch of the western sand lance Ammodytes japonicus in the eastern Seto Inland Sea, Japan, has shown a decreasing trend since the 1990s. To examine whether food shortage was the main cause for the catch decrease, we investigated the condition factor of the age‐0 fish at the beginning of the estivation period (late July) in Harima‐Nada, eastern Seto Inland Sea, for 10 years from 2008 to 2017. The mean abundance of copepods as food for the age‐0 fish during the fish growth period (from February to June) around the estivation area was also determined. The condition factor showed a significant decrease, and values for 2011 and later years were mostly lower than the known minimum threshold (4.2) for maturation. In the recent 4 years from 2013 to 2016, the mean copepod abundance was much lower than values for the other years. The condition factor showed a significant positive correlation with the copepod abundance. These results indicate that decline of western sand lance catch after 1990 was caused mainly by food shortage.

中文翻译：

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在过去十年中，日本西部沙矛鱼（Ammodytes japonicus）的条件因子年际减少：限制捕捞量的证据

西方沙矛鱼的年度捕获自1990年代以来，日本濑户内海东部地区的水量呈下降趋势。为了检查食物短缺是否是导致产量下降的主要原因，我们调查了濑户内海东部播磨（从7月下旬开始）在养殖期开始（7月下旬）的0龄鱼的条件因素。 2008年至2017年。还确定了co足动物在鱼类养殖区周围鱼类生长期间（2月至6月）作为0岁鱼的食物的平均丰富度。条件因子显示出显着下降，2011年及以后年份的值大多低于已知的成熟最低阈值（4.2）。从2013年到2016年的最近4年中，co足类动物的平均丰度远低于其他年份。条件因子与co足类的丰富度呈显着正相关。这些结果表明，1990年后西方沙矛捕捞量下降主要是由于粮食短缺造成的。