Fisheries Assessment and Management: A Synthesis of Common Approaches with Special Reference to Deepwater and Data-Poor Stocks

Eye lens-derived Δ14C signatures validate extreme longevity in the deepwater scorpaenid blackbelly rosefish (Helicolenus dactylopterus)

Many members of the scorpaenid subfamily: Sebastinae (rockfishes and their relatives) exhibit slow growth and extreme longevity (> 100 y), thus are estimated to be vulnerable to overfishing. Blackbelly rosefish (Helicolenus dactylopterus) is a deepwater sebastine whose longevity estimates range widely, possibly owing to different regional levels of fisheries exploitation across its Atlantic Ocean range. However, age estimation has not been validated for this species and ageing for sebastines in general is uncertain. We performed age validation of northern Gulf of Mexico blackbelly rosefish via an application of the bomb radiocarbon chronometer which utilized eye lens cores instead of more traditional otolith cores as the source of birth year Δ¹⁴C signatures. The correspondence of eye lens core Δ¹⁴C with a regional reference series was tested with a novel Bayesian spline analysis, which revealed otolith opaque zone counts provide accurate age estimates. Maximum observed longevity was 90 y, with 17.5% of individuals aged to be > 50 y. Bayesian growth analysis, with estimated length-at-birth included as a prior, revealed blackbelly rosefish exhibit extremely slow growth (k = 0.08 y^-1). Study results have important implications for the management of blackbelly rosefish stocks, as extreme longevity and slow growth imply low resilience to fishing pressure.

Rainforest metropolis casts 1,000-km defaunation shadow

Tropical rainforest regions are urbanizing rapidly, yet the role of emerging metropolises in driving wildlife overharvesting in forests and inland waters is unknown. We present evidence of a large defaunation shadow around a rainforest metropolis. Using interviews with 392 rural fishers, we show that fishing has severely depleted a large-bodied keystone fish species, tambaqui (Colossoma macropomum), with an impact extending over 1,000 km from the rainforest city of Manaus (population 2.1 million). There was strong evidence of defaunation within this area, including a 50% reduction in body size and catch rate (catch per unit effort). Our findings link these declines to city-based boats that provide rural fishers with reliable access to fish buyers and ice and likely impact rural fisher livelihoods and flooded forest biodiversity. This empirical evidence that urban markets can defaunate deep into rainforest wilderness has implications for other urbanizing socioecological systems.