Managing small-scale commercial fisheries for adaptive capacity: Insights from dynamic social-ecological drivers of change in Monterey Bay

Globally, small-scale fisheries (SSFs) are driven by climate, governance, and market factors of social-ecological change, presenting both challenges and opportunities. The ability of small-scale fishermen and buyers to adapt to changing conditions allows participants to survive economic or environmental disturbances and to benefit from optimal conditions. This study presented here identifies key large-scale factors that drive SSFs in California to shift focus among targets and that dictate long-term trends in landings. We use Elinor Ostrom’s Social-Ecological System (SES) framework to apply an interdisciplinary approach when identifying potential factors and when understanding the complex dynamics of these fisheries. We analyzed the interactions among Monterey Bay SSFs over the past four decades since the passage of the Magnuson Stevens Fisheries Conservation and Management Act of 1976. In this region, the Pacific sardine (Sardinops sagax), northern anchovy (Engraulis mordax), and market squid (Loligo opalescens) fisheries comprise a tightly linked system where shifting focus among fisheries is a key element to adaptive capacity and reduced social and ecological vulnerability. Using a cluster analysis of landings, we identified four modes from 1974 to 2012 that were dominated by squid, sardine, anchovy, or lacked any dominance, enabling us to identify external drivers attributed to a change in fishery dominance during seven distinct transition points. Overall, we show that market and climate factors drive the transitions among dominance modes. Governance phases most dictated long-term trends in landings and are best viewed as a response to changes in perceived biomass and thus a proxy for biomass. Our findings suggest that globally, small-scale fishery managers should consider enabling shifts in effort among fisheries and retaining existing flexibility, as adaptive capacity is a critical determinant for social and ecological resilience.

Diel Patterns of Patch Reef Community Dynamics in a Caribbean Back-Reef System

Back-reef seascapes represent critical habitat for juvenile and adult fishes. Patch reef, seagrass, and mangrove habitats form a heterogeneous mosaic, often linked by species that use reefs as structure during the day and make foraging migrations into soft-bottom habitat at night. Artificial reefs are used to model natural patch reefs, however may not function equivalently as fish habitat. To study the relative value of natural and artificial patch reefs as fish habitat, these communities in the Sea of Abaco, Bahamas were compared using roving diver surveys and time-lapse photography. Diel turnover in fish abundance, recorded with time-lapse photography and illuminated by infrared light, was quantified across midday, dusk, and night periods to explore possible effects of reef type (artificial vs. natural) on these patterns. Diurnal communities on natural reefs exhibited greater fish abundance, species richness, and functional diversity compared to artificial reefs. Furthermore, both types of reef communities exhibited a significant shift across the diel period, characterized by a decline in total fish density at night, especially for grunts (Haemulidae). Cross-habitat foraging migrations by diurnal or nocturnal species, such as haemulids, are likely central drivers of this twilight turnover and can represent important energy and nutrient subsidies. Time-lapse surveys provided more consistent measures of reef fish assemblages for the smaller artificial reef habitats, yet underestimated abundance of certain taxa and species richness on larger patch habitats when compared to the roving diver surveys. Time-lapse photography complemented with infrared light represent a valuable non-invasive approach to studying behavior of focal species and their fine-scale temporal dynamics in shallow-reef communities.

The Maintenance and Consequences of a Low Quality Diet in Poecilia Latipinna

The adaptive significance of herbivory in nature is not well understood. In order to document the conditions that select for an herbivorous feeding habit, we must first understand how such a diet is maintained, and the consequences of doing so. A few studies have begun to reveal mechanisms of maintaining herbivory (i.e. selective feeding, diet mixing, etc.) and the associated life history responses (i.e. growth, reproduction, etc.) in terrestrial and marine systems; however, studies of this kind are underrepresented in the freshwater literature. In this study, I use the sailfin molly (Poecilia latipinna) as a model organism to examine diet selectivity and the effects of an herbivorous diet on growth. To study food selectivity, sailfin mollies were fed either disturbed or intact periphyton mats from one of three localities within the Everglades (Water Conservation Area 3B, the Gap, or Chekika). Mats are structured with palatable algal species (i.e. greens and diatoms) comprising the inner components of the mat, and unpalatable species (i.e. cyanobacteria) comprising the outer edges. Fish gut contents were analyzed for each treatment and periphyton locality. Results suggest that when provided access to the inner components of the mats, fish preferentially eat more palatable algae. In a second experiment, effects of an herbivorous diet were examined using neonate sailfin mollies. Fish were fed either commercial food flakes, commercial algae flakes, or ground periphyton, and growth rate was measured weekly, from birth to 21 days. Fish fed the commercial diets grew at a faster rate and reached a larger final size than those fed periphyton. These results suggest that a periphyton diet is limited in nutritional elements compared to a pure algae diet and herbivorous organisms feeding upon it may experience negative effects on growth. By studying the costs and benefits of herbivory in a freshwater system, this paper contributes to a larger study of the question of why herbivory would evolve as an adaptation when seemingly inefficient compared to carnivorous and omnivorous diets.