Climate-induced habitat suitability intensifies fishing-induced life-history variation of a migratory long-lived fish

Intense fishing pressure and climate change are major threats to coastal fisheries. Larimichthys crocea (large yellow croaker) is a long-lived fish, which performs seasonal migrations from its spawning and nursery grounds along the coast of the East China Sea (ECS) to overwintering grounds offshore. This study used length-based analysis and habitat suitability index (HSI) model to evaluate current life-history parameters and overwintering habitat suitability of L. crocea, respectively. We compared both life-history parameters and overwintering HSI between recent (2019) and historical (between 1971 to 1982) to analyze the fishing pressure and climate change effects on the overall population and overwintering phase of L. crocea. In the context of overfishing, the length-based analysis indicated serious overfishing of L. crocea, characterized by reduced catch yield, size truncation, constrained distribution, and advanced maturation in the ECS, namely recruitment bottleneck. In the context of climate change, the overwintering HSI modeling results indicated that climate change has led to decreased sea surface temperature during L. crocea overwintering phase over the last half-century, which in turn led to area decrease and an offshore-oriented shifting of optimal overwintering habitat. The fishing-caused size truncation may constrain the migratory ability and distribution of L. crocea, subsequently led to the mismatch of the optimal overwintering habitat against climate change background, namely habitat bottleneck. Hence, while heavily fishing was the major cause of L. crocea fishery collapse, climate-induced overwintering habitat suitability may have intensified the fishery collapse of L. crocea population. It is important for management to take both overfishing and climate change issues into consideration when developing stock enhancement activities and policy regulations, particularly for migratory long-lived fish that share a similar life history to L. crocea. Combined with China’s current restocking and stock enhancement initiatives, we propose recommendations for future restocking of L. crocea in China.

The (un)sustainable game: An exploration of rhetorical strategies and risk communication in sustainable seafood campaigns

In the 1990s, following the Newfoundland Grand Banks cod fishery collapse along Canada’s East Coast, the first seafood sustainability certification organization was formed to address this widespread crisis. Two notable campaigns were formed shortly thereafter, both programs the projects of marine aquariums along the West Coast, and have gained significant attention: Vancouver Aquarium’s Oceanwise provides seafood recommendations to restaurants on the most sustainable choices and Monterey Bay Aquarium’s Seafood Watch, creates and disseminates consumer guides. This MRP examines the communication strategies of Seafood Watch and Ocean Wise used to encourage the consumption of sustainable seafood and promote ocean conservation. More specifically, this MRP analyzes the organizations’ use of environmental rhetoric, particularly in terms of framing and topoi, and how they communicate risk and urgency. How sustainable seafood campaigns establish credibility and rationale in the public sphere to communicate urgent, technical information surrounding fishery mismanagement is examined. This research will help inform future guidelines for social marketing campaigns to improve strategy and encourage consumer change. Recommendations for future research include the creation of evaluative programs to measure campaign effectiveness as well as an analysis of the niche markets established through the rising sustainable seafood market.

The (un)sustainable game: An exploration of rhetorical strategies and risk communication in sustainable seafood campaigns

In the 1990s, following the Newfoundland Grand Banks cod fishery collapse along Canada’s East Coast, the first seafood sustainability certification organization was formed to address this widespread crisis. Two notable campaigns were formed shortly thereafter, both programs the projects of marine aquariums along the West Coast, and have gained significant attention: Vancouver Aquarium’s Oceanwise provides seafood recommendations to restaurants on the most sustainable choices and Monterey Bay Aquarium’s Seafood Watch, creates and disseminates consumer guides. This MRP examines the communication strategies of Seafood Watch and Ocean Wise used to encourage the consumption of sustainable seafood and promote ocean conservation. More specifically, this MRP analyzes the organizations’ use of environmental rhetoric, particularly in terms of framing and topoi, and how they communicate risk and urgency. How sustainable seafood campaigns establish credibility and rationale in the public sphere to communicate urgent, technical information surrounding fishery mismanagement is examined. This research will help inform future guidelines for social marketing campaigns to improve strategy and encourage consumer change. Recommendations for future research include the creation of evaluative programs to measure campaign effectiveness as well as an analysis of the niche markets established through the rising sustainable seafood market.

The population dynamics of the red porgy Pagrus pagrus along southern Brazil, before its fishery collapse in the 1980s: a baseline study

The intense exploitation since 1972 of the formerly only slightly exploited protogynous hermaphroditic fish Pagrus pagrus (L.) in southern Brazil has led in less than a decade to the collapse of the fishery, with no recovery four decades later. In this study we analized the age structure, growth, reproduction and mortality of the species were studied based on samples collected from 1976 to 1985 to provide a baseline before the onset of overexploitation. Maximum estimated ages were 21 and 26 years based on scale and otolith readings, respectively. Mean total length (TL) at age did not differ between males and females, while hermaphrodites were smaller. The von Bertalanffy growth coefficients for all fish (immature, females, hermaphrodites and males) were L∞ = 447 mm, k = 0.204 and t0 = −1.134 yr. Change in growth was observed during the study period. Females were dominant at all sizes, hermaphrodites were only present up to intermediate sizes, and males, despite being infrequent at small sizes, made up over 40% among the larger specimen (TL > 400 mm). Spawning took place mainly in late spring and condition factors were lower after spawning. Natural mortality was estimated as M = 0.173 yr−1 based on the von Bertalanffy growth parameters. Total mortality (Z) and exploitation rate (E) estimated from catch curves of fully recruited red porgies aged five to ten years increased from 0.24 yr−1 and 28% before 1973 to 0.49 yr−1 and 63% in the following years. Two distinct scale and otolith patterns, one with well-marked annuli and another with faint or absent annuli, suggested that the red porgy stock off southern Brazil might not be homogeneous and may include subpopulations that do not fully mix.

Fishery collapse, recovery, and the cryptic decline of wild salmon on a major California river

Fall-run Chinook salmon (Oncorhynchus tshawytscha) from the Sacramento–San Joaquin River system form the backbone of California’s salmon fishery and are heavily subsidized through hatchery production. Identifying temporal trends in the relative contribution of hatchery- versus wild-spawned salmon is vital for assessing the status and resiliency of wild salmon populations. Here, we reconstructed the proportion of hatchery fish on natural spawning grounds in the Feather River, a major tributary to the Sacramento River, using strontium isotope (87Sr/86Sr) ratios of otoliths collected during carcass surveys from 2002 to 2010. Our results show that prior to the 2007–2008 salmon stock collapse, 55%–67% of in-river spawners were of hatchery origin; however, hatchery contributions increased drastically (89%) in 2010 following the collapse. Data from a recent hatchery marking program corroborate our results, showing that hatchery fish continued to dominate (∼90%) in 2011–2012. Though the rebound in abundance of salmon in the Feather River suggests recovery of the stock postcollapse, our otolith chemistry data document a persistent decline of wild spawners, likely leading to the erosion of locally adapted Feather River salmon populations.

Timely Events in Their Interrelation to Paddlefish and Sturgeon Harvest from 1945-2010

Due to the high amounts of harvest of natural fish populations, overexploitation can occur and subsequently lead to depleted fisheries. This is especially true for commercially exploited roe-bearing species that exhibit late age at maturation and intermittent spawning. Overexploitation can create an imbalance in natural ecosystem function and in turn jeopardize the livelihood of commercial fishers. Despite the problems created by overexploitation, trends of commercial harvest on large inland river roe-bearing populations have received minimal attention. As such, we evaluated trends in commercial fishing data from 1945-2010 for two roe-bearing species (paddlefish Polyodon spathula and shovelnose sturgeon Scaphirhynchus platorynchus) from two of the largest inland rivers in North America (Mississippi River and Missouri River) adjacent to Missouri. Commercial sturgeon and paddlefish catch has varied from ∼160 to 35,150 kg over the course of the 55-year duration. Abnormally high catches corresponded to initiation of worldwide caviar markets, onset of extensive regulations on the Missouri and Mississippi rivers, and the Caspian Sea fishery collapse; respectively. Further, our results suggest that the harvest of sturgeon and paddlefish have increased since 1945 and may be influenced by local, regional, and international events. Despite the increase in harvest and the possibility of overharvest, commercial fishing regulations have not been thoroughly evaluated for effectiveness. Further evaluation of current management and regulations of these paddlefish and sturgeon fisheries is suggested, especially considering these fisheries may be influenced by local, regional, and international events. Taking potentially influential events into consideration when evaluating and implementing regulations and authorizing commercial harvest permits are vital in sustaining a long term commercial fishery and protecting the livelihood of commercial fishers.