Community-led management in small-scale fisheries represents an alternative approach to marine ecosystem conservation. This work examines the effectiveness of community-led marine reserves (MRs) by comparing kelp forest canopy coverage and predator populations between two regions with different social-ecological conditions along the Pacific coast of Baja California, Mexico. We analyzed kelp canopy coverage from 2004 to 2023, spanning periods before, during, and after extreme marine heatwaves (2014–2016). Additionally, we compared the density, size, and biomass of three key predator species (spiny lobster, California sheephead, and horn shark) between community-led MRs and federally managed marine protected areas (MPAs). Our analyses revealed significant regional differences in kelp forest coverage recovery following extreme warming events, with the southern region maintaining historical coverage levels while the northern region showed a 95% decline in 2023. Community-led MRs maintained significantly higher densities and biomass of predator species compared to federally managed areas, with spiny lobsters and horn sharks completely absent from northern MPAs and California sheephead showing larger sizes in community-led MRs. These findings demonstrate that community-led MRs maintain predator populations, which may be crucial for future management scenarios given the importance of predator–prey relationships in kelp forest ecosystems. For policymakers, our results suggest that incorporating local governance and community-based approaches into marine management frameworks, particularly in regions with strong fishing cooperatives and traditional management practices, could enhance conservation outcomes. This study provides evidence from the Global South that locally managed, participatory approaches can achieve effective conservation outcomes, offering insights for regions facing similar challenges in balancing resource use with ecosystem protection.

Around the world, abalone species are a highly valuable marine resource. In recent years, abalone fisheries in the Northeast Pacific have suffered massive mortalities because of environmental factors. Aquaculture has been proposed as a solution to stop the collapse of this multimillion-dollar resource. Moreover, it has been shown widely that coculturing two or more species can increase the productivity of the resources cultured. The aim of this study was to test whether the growth rates of the green abalone Haliotis fulgens would increase when cocultured with the warty sea cucumber Apostichopus parvimensis. Growth rates of juvenile abalone increased by 29% in the presence of medium densities of A. parvimensis; however, coculture settings are not common in the Northeast Pacific. To our knowledge, this is the first coculture reported of these two species. Thus, these findings provide relevant information to promote innovative strategies for sustainable production of food.

Kelp forests are experiencing extreme declines globally, yet local social-ecological factors may mediate their responses to climate perturbations. Using a combination of long-term field surveys (2016–2023) and satellite data (2004–2023), we examined the regional effects of the 2014–2016 marine heatwaves regime on kelp forest ecosystems along a 600 km latitudinal gradient in Baja California, Mexico. We documented three distinct geographical subregion trajectories: (1) a remarkable resilience of giant kelp Macrocystis pyrifera , at its thermal limits in the southern subregion, recovering 95% of the historical canopy area despite experiencing the highest temperatures; (2) understory-dominated state in the mid-subregion, with a 96% decrease in M. pyrifera canopy, where understory brown macroalgae filled the ecological niche left by declining giant kelp, maintained by moderate herbivore densities; and (3) a shift to an urchin barren alternative stable state in the northern subregion, characterized by a 2,485% increase in herbivore densities from 2016 to 2023 —dominated by purple sea urchin Strongylocentrotus purpuratus (44%)— and a 95% reduction in giant kelp canopy area compared to pre-warming baseline. The southern subregion’s resilience was associated with high predators’ (10.26 ± 5.63 per 60 m²) and low herbivores’ (25.20 ± 8.89 per 60 m²) densities, dominated by turban snails Megastraea spp. (83%) with S. purpuratus absent. In contrast, the northern subregion’s shift from kelp forests to urchin barrens coincided with low predator abundances (5.05 ± 2.32 per 60 m²), potentially linked to fragmented fisheries management. Our findings challenge the assumption that range-edge populations are inherently more vulnerable to warming and underscore how local biological factors and management approaches can either enhance or compromise ecosystem resilience to climate stress. These divergent trajectories suggest that while temperature acts as an initial driver of change, the persistence of alternative states is governed by ecological feedback involving predator-herbivore dynamics, herbivores’ assemblages, and management contexts, providing insights for developing climate-adaptive conservation strategies under intensifying global environmental change.

In recent decades, global abalone aquaculture has significantly increased, while wild abalone fishery landings have decreased drastically, shifting production from fishing to farming. In California (USA) and Baja California (Mexico), overfishing and climate changelinked diseases are thought to be responsible for mass mortalities and significant declines in abalone fisheries landings. Conservation aquaculture is an option for enhancing abalone populations through captive propagation and cage mariculture with subsequent restockings into the wild. To test, inform, and promote innovative sustainable seafood production strategies in the Northeastern Pacific, we designed an experimental mariculture system at San Jeronimo Island, Baja California. We explored the feasibility of rearing juvenile red abalone, Haliotis rufescens, in a near-shore mariculture cage-based production system to supply individuals for local restoration programs. We tested the effects of 2 different depths, surface and bottom (5 m), and 3 macroalgal diets (Macrocystis pyrifera, Eisenia arborea, and a mixed diet of Pelagophycus porra with M. pyrifera) on the survival and growth of juvenile red abalone (32 ± 3.33 mm in shell length) inside cages attached to a long-line system. Over the 90-d experiment, survival was 99% for the surface treatment and 95% for the bottom treatment. Mean daily increment in shell length was 93 ± 12 µm·d–1 in surface cages and 82 ± 13 µm·d–1 in bottom cages. Depth did not affect growth or survival. Growth was highest using the E. arborea diet (99 ± 7 µm·d–1) but not significantly different from the M. pyrifera and mixed diets (88 ± 10 and 74 ± 13 µm·d–1, respectively). High survivorship and growth indicate that San Jeronimo Island can support cage-based mariculture of red abalone and that this strategy may be a useful tool in developing climate-resilient abalone restoration solutions aimed at bolstering seafood production.

Abalone is one of the most important small‐scale fisheries in Mexico and is challenged by multiple stressors. For example, the loss of the native main food, Macrocystis pyrifera, and the subsequent takeover of non‐indigenous algae species represent a major threat to abalone growth and survival. In Baja California, Mexico two introduced macroalgae, Undaria pinnatifida and Sargassum horneri have become common in the past decade with unknown consequences on native herbivores. In this work, we explored the effect of these invasive algae on the growth and survival of juvenile red abalone, Haliotis rufescens. One hundred and ten juvenile red abalone were tagged and fed with invasive algae U. pinnatifida and S. horneri , and a control with M. pyrifera . Then, the shell length, body weight, and survivorship were assessed monthly for 90 days. Results show that abalone fed U. pinnatifida had a total growth in length, weight, and survivorship, similar to those fed native M. pyrifera . In contrast, abalone fed S. horneri had significantly lower overall performance. Marine heatwaves and other climatic impacts are expected to favour the establishment of invasive species. These results may be relevant to inform local fisheries and management efforts in this area under future scenarios.

Marine reserves (MRs) are implemented worldwide to protect, restore, and manage marine ecosystems and species. However, it is important to document the positive effects those marine reserves have on slow-growth, temperate invertebrates such as abalone. Abalone, Haliotis spp., are marine gastropods of high economic value extracted worldwide for decades, which has led to fisheries-driven population decreases. In this work, we focused on a case study and assessed the short-term (1–2 years) effects of marine reserves established and managed by a local fishing cooperative at Guadalupe Island, Mexico. We evaluated the population status of green abalone, H. fulgens, by conducting (1) an assessment of the green abalone population around Guadalupe Island through subtidal monitoring and (2) an evaluation of the effect of two recently established marine reserves on population parameters such as the increase in density (individuals·m²), biomass, number of aggregated abalone, egg production, and proportion of individuals bigger than 150 mm (minimum harvest size) compared to fished areas. To assess the population around Guadalupe Island, we surveyed 11,160 m² during 2020 and 2021. We recorded 2327 green abalones with a mean ± SE shell length of 135.978 ± 0.83 mm and a mean density of 0.21 ± 0.02 individuals·m². All variables were statistically higher at the MRs except for shell length in 2021. In this work, we report for the first time the green abalone population status at Guadalupe Island and a positive short-term biological response to community-based marine reserves. This study suggests that a network of MRs combined with good management could help abalone populations in the short term in Guadalupe Island, potentially leading to more sustainable fishing practices and social-ecological resilience.