Climate change and deoxygenation are affecting fish stocks on a global scale, but disentangling the impacts of these stressors from the effects of overfishing is a challenge. This study was conducted to distinguish between climate change and mismanagement as possible causes for the drastic decline in spawning stock size and reproductive success in cod (Gadus morhua) and herring (Clupea harengus) in the Western Baltic Sea, when compared with the good or satisfactory status and reproductive success of the other commercial species in the area. Available data on water temperature, wind speed, and plankton bloom during the spawning season did not reveal conclusive correlations between years with good and bad reproductive success of cod or herring. Notably, the other commercial species in the area have very similar life history traits suggesting similar resilience against stress caused by climate change or fishing. The study concludes that severe, sustained overfishing plus inappropriate size selectivity of the main fishing gears have caused the decline in spawning stock biomass of cod and herring to levels that are known to have a high probability of impaired reproductive success. It is pointed out that allowed catches were regulated by management and adhered to by the fishers, meaning that unregulated fishing did not occur. Thus, mismanagement (quotas that were too high and gears that selected too small sizes) and not climate change appears to be the primary cause of the bad status of cod and herring in the Western Baltic Sea.

气候变化和脱氧正在全球范围内影响鱼类种群，但将这些压力源的影响与过度捕捞的影响分开是一项挑战。本研究旨在区分气候变化和管理不善可能导致鳕鱼 ( Gadus morhua ) 和鲱鱼 ( Clupea harengus )产卵量急剧下降和繁殖成功的可能原因。) 在波罗的海西部，与该地区其他商业物种的良好或令人满意的状况和繁殖成功相比。在产卵季节，有关水温、风速和浮游生物繁殖的现有数据并未揭示年份与鳕鱼或鲱鱼繁殖成功与否之间的决定性相关性。值得注意的是，该地区的其他商业物种具有非常相似的生活史特征，表明对气候变化或捕鱼造成的压力具有相似的复原力。该研究得出的结论是，严重、持续的过度捕捞以及主要渔具尺寸选择不当导致鳕鱼和鲱鱼产卵种群生物量下降到已知极有可能影响繁殖成功的水平。需要指出的是，允许的捕捞量由管理层管理并由渔民遵守，这意味着没有发生无管制的捕捞活动。因此，管理不善（配额过高和渔具选择过小的规格）而非气候变化似乎是造成西波罗的海鳕鱼和鲱鱼状况不佳的主要原因。