Marine Protection Induces Morphological Variation in the California Moray, Gymnothorax mordax

Abstract

The effectiveness of marine protected areas (MPAs) on the general health and conservation of species, habitats, and community interactions is of great interest to researchers, managers, and recreationalists. However, the ecological and behavioral diversity of vertebrate predators of southern California kelp forests limits our ability to make general conclusions about MPA effectiveness across a variety of species. Identifying and studying species with extreme feeding habits or prey-capture strategies may offer greater insight into predator-prey relationships and reveal the trophic importance of an animal in the larger community. Moray eels (family Muraenidae) have been shown to have morphological and behavioral adaptations that allow them to consume large prey whole, identifying them as important predators. From 2015-2018, we studied the health and feeding behavior of a long-lived, elusive, and benthic kelp forest predator, the California moray eel (Gymnothorax mordax). We trapped eels inside and outside of Blue Cavern Onshore State Marine Conservation Area, an MPA on the northwest side of Santa Catalina Island, CA which prohibits the take of any species. Over four years, we captured 1,736 eels. Overall, we found that morays were longer, older, heavier, had higher body condition and were found in greater abundance within the MPA. Although fish comprised the majority of their summer diet, morays outside of the MPA were consuming a more diverse set of fish, while kelp bass comprised more than half of the diet for morays inhabiting the MPA. Additionally, we found that morays within the MPA had larger relative vertical gape distances and narrower heads. Our recapture data support the high site fidelity of morays, indicating that their diet and morphology are influenced by their local community. While the majority of morays are thriving in the MPA, as suggested by their robust sizes and longevity, high abundance appears to result in higher frequencies of cannibalism, the presence of an undescribed disease, and lower growth rates. Our results suggest that the MPA affects the life history of morays and may select for an alternative feeding strategy in which eels develop larger vertical gape distances, smaller adductor muscles, and a specialized diet which is presumably influenced by the local environment. In addition, observations of cannibalistic behavior and species-specific disease provide us with important insight into natural factors that may still regulate populations removed from anthropogenic disturbances such as fishing.

Heavy, Bulky, or Both: What Does “Large Prey” Mean to Snakes?

“…We conclude that the term large prey is always ambiguous and should be replaced with the words heavy, bulky, or both, which in common parlance signify just what they mean here; Arnold's (1993:103-111) discussion of Besides foraging theory and other conceptual realms, MBT might be applicable to additional gape-limited predators. Possible examples include frogfishes (Antennariidae; Pietsch and Arnold, 2020:451), lizardfishes (Synodontidae; Soares et al, 2003), venomous deep-sea eels (Monognathidae; Bertelsen and Nielsen, 1987), morays (Muraenidae; Diluzio et al, 2017;Higgins et al, 2018;Mehta et al, 2020), some frogs (e.g., Ceratophrys; Duellman and Lizana, 1994), certain varanids and helodermatids (Greene, 1986a;Repp and Schuett, 2009), and some birds (e.g., Roadrunner [Geococcyx californianus]; Holte and Houck, 2000).…”

“…Several goals justify gathering diet data, from answering questions about morphology, physiology, ecology, ethology, evolution, and conservation to furthering nature appreciation with public outreach. Moreover, different applications might prioritize certain information—prey ID for ecological questions (e.g., Greene and Jaksic, 1983; Luiselli, 2006a; Pinto-Cuelho et al, 2021), RPM for foraging behavior (e.g., Arnold, 1993; Andreadis and Burghardt, 2005; Loughran et al, 2013; Glaudas et al, 2019), RPM and RPB for evolutionary and functional morphology (Cundall and Greene, 2000; Vincent et al, 2006a; Cundall et al, 2014; Moon et al, 2019; Gripshover and Jayne, 2021; Cundall and Irish, 2022; Jayne et al, 2022), and all of them for conservation and education (e.g., Greene, 1997, 2003, 2013; Clayton and Myers, 2015; Mehta et al, 2020). MBT is clearly germane to many aspects of snake biology, and yet its key parameters often have gone unmeasured, perhaps in part because Greene (1983a) ineffectively portrayed them.…”

Protection from fishing improves body growth of an exploited species

“…This is a necessary study design for disentangling the effects of harvest selection and environmental factors on phenotypic traits [4]. In the marine environment, there is now ample evidence that marineprotected areas (MPAs) can improve body size and other morphological traits [24,[30][31][32], but less is known about how life-history traits, such as somatic growth rate, is affected [33,34]. Is the increased body size in MPAs solely due to the upheaval of fishing mortality, or is it also modulated by shifts in somatic growth?…”