Global shark fishing mortality still rising despite widespread regulatory change.

Over the past two decades, sharks have been increasingly recognized among the world's most threatened wildlife and hence have received heightened scientific and regulatory scrutiny. Yet, the effect of protective regulations on shark fishing mortality has not been evaluated at a global scale. Here we estimate that total fishing mortality increased from at least 76 to 80 million sharks between 2012 and 2019, ~25 million of which were threatened species. Mortality increased by 4% in coastal waters but decreased by 7% in pelagic fisheries, especially across the Atlantic and Western Pacific. By linking fishing mortality data to the global regulatory landscape, we show that widespread legislation designed to prevent shark finning did not reduce mortality but that regional shark fishing or retention bans had some success. These analyses, combined with expert interviews, highlight evidence-based solutions to reverse the continued overexploitation of sharks.

Evidence of increasing juvenile white sharks' (Carcharodon carcharias) habitat use at the Northern Channel Islands.

Juvenile white sharks (Carcharodon carcharias) typically aggregate along coastal beaches; however, high levels of recruitment and shifting oceanographic conditions may be causing habitat use expansions. Telemetry data indicate increased habitat use at the Northern Channel Islands (California, USA) by juvenile white shark that may be in response to increased population density at aggregation locations, or anomalous oceanographic events that impact habitat use or expand available habitat. Findings illustrate the need for long-term movement monitoring and understanding drivers of habitat use shifts and expansion to improve ecosystem management.

Using acoustic telemetry to quantify potential contaminant exposure of Vermilion Rockfish (Sebastes miniatus), Hornyhead Turbot (Pleuronichthys verticalis), and White Croaker (Genyonemus lineatus) at wastewater outfalls in southern California.

Contaminant Exposure Models (CEMs) were developed to predict population-level tissue contaminant concentrations in fishes by pairing sediment-bound contaminant concentrations (DDTs, PCBs) and fine-scale acoustic telemetry data from a habitat-associated species (Vermilion Rockfish, Sebastes miniatus), nomadic flatfish species (Hornyhead Turbot, Pleuronichthys verticalis), and nomadic benthic/midwater schooling species (White Croaker, Genyonemus lineatus) tagged near wastewater outfalls in southern California. Model results were compared to contaminant concentrations in tissue samples. The CEMs developed require further refinement before implementation into management efforts but may act as steppingstones to help shift primary monitoring methods away from the regular field collection of fish for tissue contaminant analyses and towards behavioral modeling and habitat mapping. We also developed Kernel Density Estimates that can be used by managers immediately to identify regions that contribute most to contaminant exposure in species of concern. Prioritizing remediation efforts in these areas are likely to be most effective at improving fish health.

Evidence of artificial habitat use by a recovering marine predator in southern California.

The giant sea bass Stereolepis gigas Ayres 1859 (GSB) is a critically endangered top marine predator in California. Since protection in 1982 and 1994, the population has appeared to increase, and individuals within a growing population may expand their ranges to new habitats to reduce intraspecific competition and increase foraging opportunities. In 2016-2018, two GSB tagged with acoustic transmitters were detected at artificial reefs for periods of up to 3 months during October-March, and one individual travelled 53 km from an offshore island to mainland California in 56 h. Artificial reefs may provide important foraging opportunities for these protected marine predators as they recover from exploitation.