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.
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·m
), 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 m
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·m
. 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.
There are very few studies reporting isotopic trophic discrimination factors and turnover rates for marine elasmobranchs. A controlled laboratory experiment was conducted to estimate carbon and ...nitrogen isotope trophic discrimination factors and isotope turnover rates for blood, liver, muscle, cartilage tissue, and fin samples of neonate to young-of-the-year leopard sharks (
Triakis semifasciata
). Trophic discrimination factors varied (0.13‰–1.98‰ for δ
13
C and 1.08‰–1.76‰ for δ
15
N). Tissues reached or were close to isotopic equilibrium to the new diet after about a threefold biomass gain and 192 days. Liver and blood exhibited faster isotope turnover than muscle, cartilage tissue, and fin samples, and carbon isotopes turned over faster than those of nitrogen. Metabolic turnover contributed substantially to isotopic turnover, which differs from most reports for young marine teleosts. We modeled the relationship between muscle turnover rates and shark size by coupling laboratory results with growth rate estimates for natural populations. Model predictions for small, medium, and large wild leopard sharks indicate the time to isotopic equilibrium is from one to several years.
As a result of being hunted, animals often alter their behaviour in ways that make future encounters with predators less likely. When hunting is carried out for conservation, for example to control ...invasive species, these behavioural changes can inadvertently impede the success of future efforts. We examined the effects of repeated culling by spearing on the behaviour of invasive predatory lionfish (Pterois volitans/miles) on Bahamian coral reef patches. We compared the extent of concealment and activity levels of lionfish at dawn and midday on 16 coral reef patches off Eleuthera, The Bahamas. Eight of the patches had been subjected to regular daytime removals of lionfish by spearing for two years. We also estimated the distance at which lionfish became alert to slowly approaching divers on culled and unculled reef patches. Lionfish on culled reefs were less active and hid deeper within the reef during the day than lionfish on patches where no culling had occurred. There were no differences at dawn when removals do not take place. Lionfish on culled reefs also adopted an alert posture at a greater distance from divers than lionfish on unculled reefs. More crepuscular activity likely leads to greater encounter rates by lionfish with more native fish species because the abundance of reef fish outside of shelters typically peaks at dawn and dusk. Hiding deeper within the reef could also make remaining lionfish less likely to be encountered and more difficult to catch by spearfishers during culling efforts. Shifts in the behaviour of hunted invasive animals might be common and they have implications both for the impact of invasive species and for the design and success of invasive control programs.
Cannonball jellyfish has become the target of an important seasonal fishery in the Gulf of California. Research has focused mainly on biological and management aspects, yet linkages and dynamics ...between social and ecological components have received less attention. Based on an analysis of stakeholder perceptions and its comparison with available quantitative data, this study provides a holistic view of the fishery and its actors as part of a complex adaptive system. Stakeholders include artisanal fishers, owners of improvised and permanent processing plants, foreign buyers and funders, local managers, Mexican management entities, women, and Indigenous communities. Policy guidelines and management actions must address sustainability within various dimensions as understood by those interviewed: social equity, economic benefits, and environmental responsibility. To transition to sustainability, a transdisciplinary research approach is needed to provide management advice and to strengthen fishery governance through co-management decision-making strategies.
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•The cannonball jellyfish fishery in Sonora is as important as the shrimp fishery.•Stakeholders are concerned about jellyfish management due to its high variability.•Interdependence of ecological and social elements make jellyfish fishery complex.•Inter and transdisciplinary management strategies are required in the jellyfish fishery.•Fishery governance and sustainability can improve through adaptative co-management.
We evaluated whether the trophic level and feeding grounds (coastal versus offshore) of white and shortfin mako sharks captured in the northern Mexican Pacific varied as a function of size using ...carbon (δ13C values) and nitrogen (δ15N values) stable isotope analysis of soft tissues. A step increase in δ15N values was observed at approximately 85 cm TL and 150–170 cm TL for shortfin mako and white sharks, respectively, consistent with the dilution of the maternal isotopic signal following the incorporation of exogenous food. Shortfin mako and white shark muscle tissue and whole blood were enriched in 15N as a function of size, which is consistent with increasing trophic level, but this pattern may be confounded by differences in habitat. To infer differences in foraging habitat throughout life, we compared isotope ratios of liver and blood fractions with those of white muscle tissue; these tissues have relatively faster and slower isotope turnover rates, respectively. Whole blood and muscle δ13C values of small white sharks (<200 cm total length) caught near the coast suggested benthic foraging. Very limited differences between δ13C values of muscle tissue and whole blood from small and medium mako (<196 cm TL) and small white sharks indicated equilibrium to local feeding grounds. In contrast, differences in the δ13C values of liver tissue from small and medium mako and small white sharks indicated changes in diet or feeding grounds. The δ13C values of plasma and muscle tissue of large white sharks (>350 cm total length) caught offshore indicate feeding in coastal and oceanic areas and are consistent with recent migration to pelagic feeding grounds. Our study provides insight into size‐based habitat use and migration patterns of two species of migratory sharks for which there is limited information, particularly in their nursery grounds in Mexican waters.
Indo-Pacific lionfish (Pterois volitans and P. miles) are invasive predators established throughout the Wider Caribbean. They have already caused significant ecological impacts and have the potential ...to affect local economies that depend on coral reefs. Snorkeling and scuba diving are important activities that rely on aesthetically pleasant reefs. We asked whether lionfish-invaded reefs have lower aesthetic value and whether fees to help control the invasion might be acceptable to recreational divers and snorkelers in the Mexican Caribbean. To do so, we conducted a choice experiment in which tourists were asked to indicate their preferences for coral reef images with varying attributes that can be affected by lionfish. We specified a priori two classes of respondents, i.e. snorkelers and divers, but two latent classes of recreational divers (casual vs. committed) emerged on the basis of their preferences. Tourist age, commitment to snorkeling /diving, and lionfish awareness explained class membership. Casual divers and snorkelers preferred reefs with lionfish and accepted their impacts on the reefs. In contrast, committed divers disliked lionfish and associated impacts, and would elect to dive elsewhere if such impacts were high. Casual divers and snorkelers preferred options with low lionfish control fees, while committed divers were willing to pay high fees. Our results indicate potential economic impacts of the lionfish invasion in regions that depend on reef-related tourism, and that lionfish control fees might be acceptable to some but not all recreational users. However, because all tourists favored to a greater extent reef features that can be affected detrimentally by lionfish than they favored lionfish themselves, we predict that managing the lionfish invasion should be beneficial to the local reef tourism industry.
The shifting baseline syndrome describes a gradual lowering of human cognitive baselines, as each generation accepts a lower standard of resource abundance or size as the new norm. There is strong ...empirical evidence of declining trends of abundance and body sizes of marine fish species reported from docks and markets. We asked whether these widespread trends in shrinking marine fish are detectable in popular English-language media, or whether news writers, like many marine stakeholders, are captive to shifting baselines. We collected 266 English-language news articles, printed between 1869 and 2015, which featured headlines that used a superlative adjective, such as 'giant', 'huge', or 'monster', to describe an individual fish caught. We combined the reported sizes of the captured fish with information on maximum species-specific recorded sizes to reconstruct trends of relative size (reported size divided by maximum size) of newsworthy fishes over time. We found some evidence of a shifting baseline syndrome in news media over the last 140 years: overall, the relative length of the largest fish worthy of a headline has declined over time. This pattern held for charismatic fish species (e.g. basking sharks, whale sharks, giant mantas), which are now reported in the media at smaller relative lengths than they were near the turn of the 20th century, and for the largest species under high risk of extinction. In contrast, there was no similar trend for pelagic gamefish and oceanic sharks, or for species under lower risk of extinction. While landing any individual of the large-bodied 'megafish' may be newsworthy in part because of their large size relative to other fish species, the 'megafish' covered in our dataset were small relative to their own species-on average only 56% of the species-specific maximum length. The continued use in the English-language media of superlatives to describe fish that are now a fraction of the maximum size they could reach, or a fraction of the size they used to be, does reflect a shifting baseline for some species. Given that media outlets are a powerful tool for shaping public perception and awareness of environmental issues, there is a real concern that such stories might be interpreted as meaning that superlatively large fish still abound.
Low diversity among scientists and practitioners is rampant in conservation. Currently, conservation professionals do not reflect the same diversity of perspectives and experiences of the world as ...the communities who bear the largest burden for implementing—or adverse consequences for failing to implement—conservation action. Acknowledging and describing the problem is important. But policies and programmes must also be put in place to correct it. Here, we highlight some measurable benefits of workforce diversity, and give an overview of some of the barriers to inclusion in marine conservation that help perpetuate low workforce diversity. Importantly, we underscore actions that both individuals and groups can take to alleviate such barriers. In particular, we describe the establishment of an online Marine Diversity Network, which conference participants proposed during a focus group meeting at the 4th International Marine Conservation Congress. The network will serve to bring together people from across the globe, from a variety of backgrounds, and from all career stages, to share knowledge, experiences and ideas, to provide and receive mentorship in marine conservation, and to forge new collaborations. Removing barriers to diverse participation requires coordinated, mindful actions by individuals and organizations. We hope that the proposed network and other actions presented in this paper find widespread support, and that they might serve both as inspiration and guide to other groups concerned with increasing diversity and inclusivity.
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