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Abstract Understanding how future ocean conditions will affect populations of marine species is integral to predicting how climate change will impact both ecosystem function and fisheries management. Fish population dynamics are driven by variable survival of the early life stages, which are highly sensitive to environmental conditions. As global warming generates extreme ocean conditions (i.e., marine heatwaves) we can gain insight into how larval fish growth and mortality will change in warmer conditions. The California Current Large Marine Ecosystem experienced anomalous ocean warming from 2014 to 2016, creating novel conditions. We examined the otolith microstructure of juveniles of the economically and ecologically important black rockfish ( Sebastes melanops ) collected from 2013 to 2019 to quantify the implications of changing ocean conditions on early growth and survival. Our results demonstrated that fish growth and development were positively related to temperature, but survival to settlement was not directly related to ocean conditions. Instead, settlement had a dome-shaped relationship with growth, suggesting an optimal growth window. Our results demonstrated that the dramatic change in water temperature caused by such extreme warm water anomalies increased black rockfish growth in the larval stage; however, without sufficient prey or with high predator abundance these extreme conditions contributed to reduced survival. 

Otolith microstructure analysis provides critical biological and ecological information about the early life history of fishes. This information is particularly important to interpret and predict population dynamics for socio‐economically important fisheries species; nonetheless, several key assumptions underpin the use of otolith techniques. The authors validated the use of this analysis for cabezon (Scorpaenichthys marmoratus; Ayres, 1854), a long‐lived, large‐bodied cottid constituent of nearshore fisheries from Baja California, Mexico, to Alaska, USA. To test three critical assumptions, the authors coupled otolith and morphometric analyses from an opportunistic rearing study of cabezon eggs and larvae with a long‐term time series of juvenile cabezon field collections. The authors confirmed the daily otolith increment deposition in laboratory‐reared larvae, identified the timing of first otolith increment deposition and examined the relationship between otolith growth and somatic growth in field‐collected juveniles, validating the use of otolith microstructure analysis in biological and ecological interpretations of early life‐history traits for this species. The findings of this study also indicated that the absorption of yolk‐sac reserves, and likely the transition to exogenous feeding, plays an important role in regulating otolith increment deposition. Finally, the authors found within‐brood size‐at‐age variation, which may be an advantage for young fish in prey‐limited environments.

 

Marine protected areas (MPAs) are a key tool for achieving goals for biodiversity conservation and human well-being, including improving climate resilience and equitable access to nature. At a national level, they are central components in the U.S. commitment to conserve at least 30% of U.S. waters by 2030. By definition, the primary goal of an MPA is the long-term conservation of nature; however, not all MPAs provide the same ecological and social benefits. A U.S. system of MPAs that is equitable, well-managed, representative and connected, and includes areas at a level of protection that can deliver desired outcomes is best positioned to support national goals. We used a new MPA framework, The MPA Guide, to assess the level of protection and stage of establishment of the 50 largest U.S. MPAs, which make up 99.7% of the total U.S. MPA area (3.19 million km²). Over 96% of this area, including 99% of that which is fully or highly protected against extractive or destructive human activities, is in the central Pacific ocean. Total MPA area in other regions is sparse – only 1.9% of the U.S. ocean excluding the central Pacific is protected in any kind of MPA (120,976 km²). Over three quarters of the non-central Pacific MPA area is lightly or minimally protected against extractive or destructive human activities. These results highlight an urgent need to improve the quality, quantity, and representativeness of MPA protection in U.S. waters to bring benefits to human and marine communities. We identify and review the state of the science, including focal areas for achieving desired MPA outcomes and lessons learned from places where sound ecological and social design principles come together in MPAs that are set up to achieve national goals for equity, climate resilience, and biodiversity conservation. We recommend key opportunities for action specific to the U.S. context, including increasing funding, research, equity, and protection level for new and existing U.S. MPAs.

 

A critical tool in assessing ecosystem change is the analysis of long‐term data sets, yet such information is generally sparse and often unavailable for many habitats. Kelp forests are an example of rapidly changing ecosystems that are in most cases data poor. Because kelp forests are highly dynamic and have high intrinsic interannual variability, understanding how regional‐scale drivers are driving kelp populations—and particularly how kelp populations are responding to climate change—requires long‐term data sets. However, much of the work on kelp responses to climate change has focused on just a few, relatively long‐lived, perennial, canopy‐forming species. To understand how kelp populations with different life history traits are responding to climate‐related variability, we leverage 35 yr of Landsat satellite imagery to track the population size of an annual, ruderal kelp,Nereocystis luetkeana, across Oregon. We found high levels of interannual variability inNereocystiscanopy area and varying population trajectories over the last 35 yr. Surprisingly, OregonNereocystispopulation sizes were unresponsive to a 2014 marine heat wave accompanied by increases in urchin densities that decimated northern CaliforniaNereocystispopulations. Some OregonNereocystis populations have even increased in area relative to pre‐2014 levels. Analysis of environmental drivers found thatNereocystispopulation size was negatively correlated with estimated nitrate levels and positively correlated with winter wave height. This pattern is the inverse of the predicted relationship based on extensive prior work on the perennial kelpMacrocystis pyriferaand may be related to the annual life cycle ofNereocystis. This article demonstrates (1) the value of novel remote sensing tools to create long‐term data sets that may challenge our understanding of nearshore marine species and (2) the need to incorporate life history traits into our theory of how climate change will shape the ocean of the future.