An overview of salmon enhancement and the need to manage and monitor natural spawning in Hokkaido, Japan

Abstract

The chum and pink salmon catches in Hokkaido, Japan have increased dramatically since the 1970s and the 1990s, respectively. In contrast, masu salmon catches have been steadily decreasing. Despite intensive hatchery development in Hokkaido, naturally spawning salmon populations persist based on results from a recent river survey. This paper focuses on the challenges of maintaining hatchery salmon populations while protecting natural chum, pink and masu salmon populations in Hokkaido. Two important initiatives related to meeting this ambitious goal are managing hatcheries in a way that minimizes negative interactions between natural and hatchery salmon populations, and initiating new efforts at restoring and rehabilitating degraded freshwater habitats. In addition, in order to maintain a balance of demand and supply in the domestic market through the exportation of extra salmon, Hokkaido has decided to enter full assessment to gain Marine Stewardship Council (MSC) certification of the Hokkaido chum salmon trap net fishery. This would involve a fundamental shift in fisheries management as practiced in Japan, specifically elevating the importance of managing the fishery in a way that conserves natural salmon populations. A key component of a new salmon management strategy is the establishment of a zone management framework based on the designation of stream units to spatially separate natural salmon from hatchery salmon to minimize negative effects of hatchery fish and to utilize effectively hatchery salmon for commercial fisheries. This effort is allied with similar initiatives in other Pacific Rim countries that are focusing on management reform to restore natural ecosystem function and maintain the coexistence of wild and hatchery salmon.

Adapting Hokkaido Hatchery Strategies to Regional Ocean Conditions Can Improve Chum Salmon Survival and Reduce Variability

“…Evidence for reduced reproductive success or survival of hatchery fi sh has accumulated in salmonids such as Atlantic salmon (Milot et al 2013), steelhead trout (Araki et al 2007), and coho salmon (Thériault et al 2011;Zimmerman et al 2015), species that tend to be reared for lengthy periods before release, although evidence for chum salmon is lacking (Berejikian et al 2009). Therefore, we need to monitor and conserve regional wild chum salmon Nagata et al 2012) and to restrict egg transplantation between different genetic populations to avoid genetic disturbance and promote the sustainable use of chum salmon resources in Hokkaido.…”

“…1; Miyakoshi et al 2013). While the number of hatchery juvenile chum salmon released increased significantly in the 1970s, release numbers have been relatively stable in each region since the 1980s Nagata et al 2012). We examined return rates for the 25 brood years from 1983 to 2007.…”

Lessons from Japan marine stock enhancement and sea ranching programmes over 100 years

“…Attention has also been directed towards seed production (Fushimi 2001; Takeuchi 2001; Le Vay et al 2007), seed quality and behaviour (Tsukamoto et al 1999), broodstock management (Taniguchi 2003, 2004), and genetic effects on wild populations (Kitada et al 2009). Reviews on salmonids have covered large-scale hatchery releases, mainly focusing on chum salmon and pink salmon; however, their emphasis was mainly on ecology, with stocking effects not fully evaluated (e.g., Kaeriyama 1999; Morita et al 2006; Kaeriyama et al 2012; Nagata et al 2012; Miyakoshi et al 2013; Kitada 2014; Morita 2014). My previous systematic review provided a perspective on economic, ecological, and genetic effects of marine stock enhancement and sea ranching programmes worldwide, including salmon (Kitada 2018), but its focus was global.…”

Effects of hatchery chum salmon fry on density-dependent intra- and interspecific competition between wild chum and masu salmon fry

“…In Hokkaido, there are well-developed hatchery programs for three native Oncorhynchus species (O. keta, O. masou, and Oncorhynchus gorbuscha), designed to increase the fishery harvest. In particular, chum salmon, which is the most stocked fish in the North Pacific Rim, is stocked into rivers in all parts of Hokkaido (Morita et al 2006;Ruggerone et al 2010;Nagata et al 2012;Miyakoshi et al 2013). Stocked chum salmon fry migrate toward the sea primarily at night, and like the wild fish, they actively forage during the daytime (Hasegawa and Takahashi 2013).…”