Cleridy E. Lennert-Cody

Marine reserve design: optimal size, habitats, species affinities, diversity, and ocean microclimate

The design of marine reserves is complex and fraught with uncertainty. However, protection of critical habitat is of paramount importance for reserve design. We present a case study as an example of a reserve design based on fine-scale habitats, the affinities of exploited species to these habitats, adult mobility, and the physical forcing affecting the dynamics of the habitats. These factors and their interaction are integrated in an algorithm that determines the optimal size and location of a marine reserve for a set of 20 exploited species within five different habitats inside a large kelp forest in southern California. The result is a reserve that encompasses approximately 42% of the kelp forest. Our approach differs fundamentally from many other marine reserve siting methods in which goals of area, diversity, or biomass are targeted a priori. Rather, our method was developed to determine how large a reserve must be within a specific area to protect a self-sustaining assemblage of exploited species. The algorithm is applicable across different ecosystems, spatial scales, and for any number of species. The result is a reserve in which habitat value is optimized for a predetermined set of exploited species against the area left open to exploitation. The importance of fine-scale habitat definitions for the exploited species off La Jolla is exemplified by the spatial pattern of habitats and the stability of these habitats within the kelp forest, both of which appear to be determined by ocean microclimate.

Strategies for fitting nonlinear ecological models in R, AD Model Builder, and BUGS

1. Ecologists often use nonlinear fitting techniques to estimate the parameters of complex ecological models, with attendant frustration. This paper compares three open-source model fitting tools and discusses general strategies for defining and fitting models. 2. R is convenient and (relatively) easy to learn, AD Model Builder is fast and robust but comes with a steep learning curve, while BUGS provides the greatest flexibility at the price of speed. 3. Our model-fitting suggestions range from general cultural advice (where possible, use the tools and models that are most common in your subfield) to specific suggestions about how to change the mathematical description of models to make them more amenable to parameter estimation. 4. A companion web site (https://groups.nceas.ucsb.edu/nonlinear-modeling/projects) presents detailed examples of application of the three tools to a variety of typical ecological estimation problems; each example links both to a detailed project report and to full source code and data.

Trade-Offs in the Design of Fishery Closures: Management of Silky Shark Bycatch in the Eastern Pacific Ocean Tuna Fishery

Bycatch--the incidental catch of nontarget species--is a principal concern in marine conservation and fisheries management. In the eastern Pacific Ocean tuna fishery, a large fraction of nonmammal bycatch is captured by purse-seine gear when nets are deployed around floating objects. We examined the spatial distribution of a dominant species in this fisherys bycatch, the apex predator silky shark (Carcharhinus falciformis), from 1994 to 2005 to determine whether spatial closures, areas where fishing is prohibited, might effectively reduce the bycatch of this species. We then identified candidate locations for fishery closures that specifically considered the trade-off between bycatch reduction and the loss of tuna catch and evaluated ancillary conservation benefits to less commonly captured taxa. Smoothed spatial distributions of silky shark bycatch did not indicate persistent small areas of especially high bycatch for any size class of shark over the 12-year period. Nevertheless, bycatch of small silky sharks (<90 cm total length) was consistently higher north of the equator during all years. On the basis of this distribution, we evaluated nearly 100 candidate closure areas between 5°N and 15°N that could have reduced, by as much as 33%, the total silky shark bycatch while compromising only 12% of the tuna catch. Although silky sharks are the predominant species of elasmobranchs caught as bycatch in this fishery, closures also suggested reductions in the bycatch of other vulnerable taxa, including other shark species and turtles. Our technique provides an effective method with which to balance the costs and benefits of conservation in fisheries management. Spatial closures are a viable management tool, but implementation should be preceded by careful consideration of the consequences of fishing reallocation.

The Ecuadorian Artisanal Fishery for Large Pelagics: Species Composition and Spatio-Temporal Dynamics.

The artisanal fisheries of Ecuador operate within one of the most dynamic and productive marine ecosystems of the world. This study investigates the catch composition of the Ecuadorian artisanal fishery for large pelagic fishes, including aspects of its spatio-temporal dynamics. The analyses of this study are based on the most extensive dataset available to date for this fishery: a total of 106,963 trip-landing inspection records collected at its five principal ports during 2008 ‒ 2012. Ecuadorian artisanal fisheries remove a substantial amount of biomass from the upper trophic-level predatory fish community of the eastern tropical Pacific Ocean. It is estimated that at least 135 thousand metric tons (mt) (about 15.5 million fish) were landed in the five principal ports during the study period. The great novelty of Ecuadorian artisanal fisheries is the “oceanic-artisanal” fleet component, which consists of mother-ship (nodriza) boats with their towed fiber-glass skiffs (fibras) operating with pelagic longlines. This fleet has fully expanded into oceanic waters as far offshore as 100°W, west of the Galapagos Archipelago. It is estimated that nodriza operations produce as much as 80% of the total catches of the artisanal fishery. The remainder is produced by independent fibras operating in inshore waters with pelagic longlines and/or surface gillnets. A multivariate regression tree analysis was used to investigate spatio-environmental effects on the nodriza fleet (n = 6,821 trips). The catch species composition of the nodriza fleet is strongly influenced by the northwesterly circulation of the Humboldt Current along the coast of Peru and its associated cold waters masses. The target species and longline gear-type used by nodrizas change seasonally with the incursion of cool waters (< 25°C) from the south and offshore. During this season, dolphinfish (Coryphaena hippurus) dominates the catches. However, in warmer waters, the fishery changes to tuna-billfish-shark longline gear and the catch composition becomes much more diverse.

Effect of mesoscale eddies and streamers on sardine spawning habitat and recruitment success off Southern and central California

We quantified the effect of mesoscale eddies and streamers on the spatial distribution of Pacific sardine spawning habitat using a merged altimetry data set and a statistical spawning habitat model. The distribution of eggs could be predicted using sea-surface temperature, chlorophyll concentration, and eddy kinetic energy (EKE) similarly to previous studies. Eddies alone did not have a significant additional or emergent effect on the probability of capturing eggs beyond these predictors. Rather, mesoscale features (eddies and streamers) entrained water with the appropriate conditions in terms of temperature, chlorophyll, and EKE. These dynamic features moved appropriate spawning habitat for sardine offshore to areas where appropriate habitat otherwise would not exist. Using centroids of predicted sardine habitat, we showed that sardine recruitment success was inversely correlated with distance from shore of predicted sardine habitat centroids. This indicates that offshore transport has a negative effect on sardine recruitment, despite expanding favorable spawning habitat further offshore.

Recent purse-seine FAD fishing strategies in the eastern Pacific Ocean: what is the appropriate number of FADs at sea?

Recent purse-seine FAD fishing strategies in the eastern Pacific Ocean: what is the appropriate number of FADs at sea? Cleridy E. Lennert-Cody*, Gala Moreno, Victor Restrepo, Marlon H. Román, and Mark N. Maunder Inter-American Tropical Tuna Commission, 8901 La Jolla Shores Drive, La Jolla, CA 92037, USA International Seafood Sustainability Foundation, 1440 G Street NW, Washington, DC 20005, USA *Corresponding author: tel: þ 1 858 546 7190; fax: þ 1 858 546 7133; e-mail: clennert@iattc.org

Sea Urchin Behavior in a Southern California Kelp Forest: Food, Fear, Behavioral Niches, and Scaling Up Individual Behavior

ABSTRACT Red and purple sea urchins (Mesocentrotus francisanus and Strongylocentrotus purpuratus) cohabit the west coast of North America and exhibit behavioral switching between sheltering, when food is abundant, and emergence and overgrazing, when food is scarce. To better understand individual urchin foraging behavior, we conducted a series of time-lapse behavioral studies within and at the edge of a resilient sea urchin barren. Photographs were taken at 15-min intervals for weeklong periods to observe behavior (1) in different microtopographic settings, (2) in response to food additions, and (3) along a spatial gradient from the leading edge of a sea urchin grazing front to ∼100 m behind it. Movement was limited for both species when crowded or in complex microtopography. Consistent differences in sheltering behaviors and diel movement patterns were observed between species in the presence and absence of food indicating behavioral niche differentiation. Red sea urchins responded to food falls at distances of at least 3m and exhibit an ability to return to shelters at similar distances. Both species exhibit (1) local movement for up to weeklong periods indicating constraints on bulk movement and grazing front formation, (2) decreased movement rates owing to crowding and microtopography analogous to traffic jams, and (3) consistent instraspecific differences in individual movement behaviors (i.e., personality). We propose how small-scale behavioral modes may scale to larger-scale local population movements and affect the dynamics of sea urchin overgrazing.