scholarly journals Protection of large predators in a marine reserve alters size-dependent prey mortality

2017 ◽  
Vol 284 (1847) ◽  
pp. 20161936 ◽  
Author(s):  
Rebecca L. Selden ◽  
Steven D. Gaines ◽  
Scott L. Hamilton ◽  
Robert R. Warner
Keyword(s):  
Size Structure ◽  
Sea Urchins ◽  
Marine Reserves ◽  
Marine Reserve ◽  
Mortality Rates ◽  
Kelp Forests ◽  
Size Dependent ◽  
Predator Size ◽  
Top Predators ◽  
Large Predators

Where predator–prey interactions are size-dependent, reductions in predator size owing to fishing has the potential to disrupt the ecological role of top predators in marine ecosystems. In southern California kelp forests, we investigated the size-dependence of the interaction between herbivorous sea urchins and one of their predators, California sheephead ( Semicossyphus pulcher ). Empirical tests examined how differences in predator size structure between reserve and fished areas affected size-specific urchin mortality. Sites inside marine reserves had greater sheephead size and biomass, while empirical feeding trials indicated that larger sheephead were required to successfully consume urchins of increasing test diameter. Evaluations of the selectivity of sheephead for two urchin species indicated that shorter-spined purple urchins were attacked more frequently and successfully than longer-spined red urchins of the same size class, particularly at the largest test diameters. As a result of these size-specific interactions and the higher biomass of large sheephead inside reserves, urchin mortality rates were three times higher inside the reserve for both species. In addition, urchin mortality rates decreased with urchin size, and very few large urchins were successfully consumed in fished areas. The truncation of sheephead size structure that commonly occurs owing to fishing will probably result in reductions in urchin mortality, which may reduce the resilience of kelp beds to urchin barren formation. By contrast, the recovery of predator size structure in marine reserves may restore this resilience, but may be delayed until fish grow to sizes capable of consuming larger urchins.

Effects of marine reserves on predator-prey interactions in central California kelp forests

2020 ◽  
Vol 655 ◽  
pp. 139-155
Author(s):  
DC Yates ◽  
SI Lonhart ◽  
SL Hamilton
Keyword(s):  
Species Interactions ◽  
Size Structure ◽  
Marine Reserves ◽  
Mortality Rates ◽  
Kelp Forests ◽  
Negative Effects ◽  
Central California ◽  
Invertebrate Predators ◽  
Predatory Fishes ◽  
Density And Biomass

Marine reserves are often designed to increase density, biomass, size structure, and biodiversity by prohibiting extractive activities. However, the recovery of predators following the establishment of marine reserves and the consequent cessation of fishing may have indirect negative effects on prey populations by increasing prey mortality. We coupled field surveys with empirical predation assays (i.e. tethering experiments) inside and outside of 3 no-take marine reserves in kelp forests along the central California coast to quantify the strength of interactions between predatory fishes and their crustacean prey. Results indicated elevated densities and biomass of invertebrate predators inside marine reserves compared to nearby fished sites, but no significant differences in prey densities. The increased abundance of predators inside marine reserves translated to a significant increase in mortality of 2 species of decapod crustaceans, the dock shrimp Pandalus danae and the cryptic kelp crab Pugettia richii, in tethering experiments. Shrimp mortality rates were 4.6 times greater, while crab mortality rates were 7 times greater inside reserves. For both prey species, the time to 50% mortality was negatively associated with the density and biomass of invertebrate predators (i.e. higher mortality rates where predators were more abundant). Video analyses indicated that macro-invertivore fishes arrived 2 times faster to tethering arrays at sites inside marine reserves and began attacking tethered prey more rapidly. The results indicate that marine reserves can have direct and indirect effects on predators and their prey, respectively, and highlight the importance of considering species interactions in making management decisions.

scholarly journals Intraspecific variation in body size does not alter the effects of mesopredators on prey

2016 ◽  
Vol 3 (12) ◽  
pp. 160414 ◽  
Author(s):  
Austin J. Gallagher ◽  
Simon J. Brandl ◽  
Adrian C. Stier
Keyword(s):  
Body Size ◽  
Size Structure ◽  
Independent Effect ◽  
Marine Food Webs ◽  
Size Dependent ◽  
Predator Attack ◽  
Predator Size ◽  
Experimental Trials ◽  
Large Predators

As humans continue to alter the species composition and size structure of marine food webs, it is critical to understand size-dependent effects of predators on prey. Yet, how shifts in predator body size mediate the effect of predators is understudied in tropical marine ecosystems, where anthropogenic harvest has indirectly increased the density and size of small-bodied predators. Here, we combine field surveys and a laboratory feeding experiment in coral reef fish communities to show that small and large predators of the same species can have similar effects. Specifically, surveys show that the presence of a small predator ( Paracirrhites arcatus ) was correlated with lower chances of prey fish presence, but these correlations were independent of predator size. Experimental trials corroborated the size-independent effect of the predator; attack rates were indistinguishable between small and large predators, suggesting relatively even effects of hawkfish in various size classes on the same type of prey. Our results indicate that the effects of small predators on coral reefs can be size-independent, suggesting that variation in predator size-structure alone may not always affect the functional role of these predators.

scholarly journals Exploitation and recovery of a sea urchin predator has implications for the resilience of southern California kelp forests

2015 ◽  
Vol 282 (1799) ◽  
pp. 20141817 ◽  
Author(s):  
Scott L. Hamilton ◽  
Jennifer E. Caselle
Keyword(s):  
Sea Urchin ◽  
Life Histories ◽  
Southern California ◽  
Size Structure ◽  
Marine Reserves ◽  
Minimum Size ◽  
Kelp Forests ◽  
Positive Effects ◽  
Management Measures ◽  
History Of

Size-structured predator–prey interactions can be altered by the history of exploitation, if that exploitation is itself size-selective. For example, selective harvesting of larger sized predators can release prey populations in cases where only large individuals are capable of consuming a particular prey species. In this study, we examined how the history of exploitation and recovery (inside marine reserves and due to fisheries management) of California sheephead ( Semicossyphus pulcher ) has affected size-structured interactions with sea urchin prey in southern California. We show that fishing changes size structure by reducing sizes and alters life histories of sheephead, while management measures that lessen or remove fishing impacts (e.g. marine reserves, effort restrictions) reverse these effects and result in increases in density, size and biomass. We show that predation on sea urchins is size-dependent, such that the diet of larger sheephead is composed of more and larger sized urchins than the diet of smaller fish. These results have implications for kelp forest resilience, because urchins can overgraze kelp in the absence of top-down control. From surveys in a network of marine reserves, we report negative relationships between the abundance of sheephead and urchins and the abundance of urchins and fleshy macroalgae (including giant kelp), indicating the potential for cascading indirect positive effects of top predators on the abundance of primary producers. Management measures such as increased minimum size limits and marine reserves may serve to restore historical trophic roles of key predators and thereby enhance the resilience of marine ecosystems.

Measure-valued solutions to size-structured population model of prey controlled by optimally foraging predator harvester

2019 ◽  
Vol 29 (09) ◽  
pp. 1657-1689
Author(s):  
Jȩdrzej Jabłoński ◽  
Dariusz Wrzosek
Keyword(s):  
Population Model ◽  
Numerical Solutions ◽  
Size Structure ◽  
Prey Size ◽  
Mortality Rates ◽  
Net Energy ◽  
Structured Population Model ◽  
Size Dependent ◽  
Structured Population ◽  
Net Energy Intake

Radon-measure-valued solutions to a size structured population model of the McKendrick–von Foerster-type are analytically studied under general assumptions on individuals’ growth, birth and mortality rates. The model is used to describe changes in size structure of zooplankton when prey size-dependent mortality rate is a consequence of a planktivorous fish foraging in low prey-density environment (commonly found in predator-controlled populations). The model of foraging is based on the optimization of the rate of net energy intake as a function of predator speed. Mortality is defined as an operator on a metric space of nonnegative Radon measures equipped with the bounded Lipschitz distance. The solutions to the size structured model of zooplankton population are studied analytically and numerically. Numerical solutions (derived using the Escalator Boxcar Train (EBT)-like schema), in particular those starting from Dirac deltas corresponding to distinct cohorts, exhibit regularization in time and convergence to the same stationary state.

The allometry of cannibalism in piscivorous fishes

2003 ◽  
Vol 60 (5) ◽  
pp. 594-602 ◽  
Author(s):  
Francis Juanes
Keyword(s):  
Upper Bound ◽  
Prey Size ◽  
Trophic Niche ◽  
Large Prey ◽  
Predator Species ◽  
Size Dependent ◽  
Predator Size ◽  
Large Databases ◽  
Widespread Phenomenon ◽  
Large Predators

Cannibalism is a widespread phenomenon that can have strong population and community effects. In this study, I compare the prey size – predator size relationships of diets with and without cannibalized prey for four piscivorous species and five populations that are commonly cannibalistic and where large databases exist. I then examine the resultant trophic niche breadths (range of relative prey size consumed) to quantify whether inclusion of cannibalized prey in the diet slows down the decline in trophic niche breadth that many large predators exhibit as they grow. When comparing diets including cannibalized prey with those without, consistent differences were found among all predator species. In all cases, the slope of the upper bound of the predator size – prey size scatters was larger for cannibal predators compared with noncannibals, suggesting selectivity for larger cannibal prey, which may be driven by higher rates of size-dependent capture success with familiar prey. The slopes of the upper bounds of the cannibal relative prey size vs. predator size scatter also tended to be larger than the upper-bound slopes for diets without conspecific prey. Finally, for all species, mean trophic breadth of diets including cannibalized prey were larger than those not including cannibal prey, suggesting that relatively large prey sizes may always be available for cannibals.

Spatially explicit mortality of California spiny lobster (Panulirus interruptus) across a marine reserve network

2012 ◽  
Vol 39 (3) ◽  
pp. 215-224 ◽  
Author(s):  
MATTHEW C. KAY ◽  
JONO R. WILSON
Keyword(s):  
Marine Reserves ◽  
Marine Reserve ◽  
Spiny Lobster ◽  
Total Mortality ◽  
Ecological Factors ◽  
Mortality Rates ◽  
Spatially Explicit ◽  
Santa Barbara Channel ◽  
Panulirus Interruptus ◽  
Reserve Network

SUMMARYStudies of marine reserves typically focus upon differences in the size and abundance of target organisms inside versus outside reserve borders, but they seldom provide spatially explicit measurements of how reserves influence mortality rates. This study investigated mortality rates for female California spiny lobster (Panulirus interruptus) at multiple sites inside and outside of three marine reserves at the Santa Barbara Channel Islands, California, USA. Mean total mortality (Z) of female lobsters was lower at sites inside reserves (Z = 0.22 [± 0.05 SE]) than at sites outside reserves (Z = 0.59 [± 0.02 SE]). Mean mortality at all sites inside reserves, and among sites near reserve centres (where Z = 0.17 [± 0.05 SE]), was similar to estimates of natural mortality for other temperate spiny lobster species. Among sites inside reserves, there was a positive relationship between mortality and proximity to reserve borders, but this relationship was absent among sites outside reserves. Mortality estimates were much more variable among sites inside reserves than at sites in fished areas. This variation is probably due to differential emigration rates from the three reserves, as well as site-specific ecological factors that influence population structure, demonstrating the importance of spatially explicit reserve sampling and understanding how ecological heterogeneity influences fisheries models.

scholarly journals Southward decrease in the protection of persistent giant kelp forests in the northeast Pacific

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Nur Arafeh-Dalmau ◽  
Kyle C. Cavanaugh ◽  
Hugh P. Possingham ◽  
Adrian Munguia-Vega ◽  
Gabriela Montaño-Moctezuma ◽  
...  
Keyword(s):  
Baja California ◽  
Marine Reserves ◽  
Fold Increase ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Central California ◽  
Northeast Pacific ◽  
The Face ◽  
High Resolution Satellite Imagery ◽  
Northeast Pacific Ocean

AbstractKelp forests are globally important and highly productive ecosystems, yet their persistence and protection in the face of climate change and human activity are poorly known. Here, we present a 35-year time series of high-resolution satellite imagery that maps the distribution and persistence of giant kelp (Macrocystis pyrifera) forests along ten degrees of latitude in the Northeast Pacific Ocean. We find that although 7.7% of giant kelp is protected by marine reserves, when accounting for persistence only 4% of kelp is present and protected. Protection of giant kelp decreases southerly from 20.9% in Central California, USA, to less than 1% in Baja California, Mexico, which likely exacerbates kelp vulnerability to marine heatwaves in Baja California. We suggest that a two-fold increase in the area of kelp protected by marine reserves is needed to fully protect persistent kelp forests and that conservation of climate-refugia in Baja California should be a priority.

scholarly journals Prey-predator size-dependent functional response: derivation and rescaling to the real world

2004 ◽  
Vol 73 (2) ◽  
pp. 239-252 ◽  
Author(s):  
Albashir A. Aljetlawi ◽  
Erik Sparrevik ◽  
Kjell Leonardsson
Keyword(s):  
Functional Response ◽  
Real World ◽  
The Real ◽  
Size Dependent ◽  
Predator Size

Impacts of recolonizing gray wolves (Canis lupus) on survival and mortality in two sympatric ungulates

2018 ◽  
Vol 96 (7) ◽  
pp. 760-768 ◽  
Author(s):  
J.A. Dellinger ◽  
C.R. Shores ◽  
M. Marsh ◽  
M.R. Heithaus ◽  
W.J. Ripple ◽  
...  
Keyword(s):  
Canis Lupus ◽  
Mule Deer ◽  
Survival Rates ◽  
Odocoileus Hemionus ◽  
Mortality Rates ◽  
Adult Survival ◽  
Mortality Data ◽  
Gray Wolf ◽  
Gray Wolves ◽  
Large Predators

There is growing recognition that humans may mediate the strength and nature of the ecological effects of large predators. We took advantage of ongoing gray wolf (Canis lupus Linnaeus, 1758) recolonization in Washington, USA, to contrast adult survival rates and sources of mortality for mule deer (Odocoileus hemionus (Rafinesque, 1817)) and white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) in areas with and without wolf packs in a managed landscape dominated by multiple human uses. We tested the hypothesis that the addition of wolves to the existing predator guild would augment predator-induced mortality rates for both ungulates. Source of mortality data from adult mule deer and white-tailed deer, respectively, revealed that wolf-related mortality was low compared with that inflicted by other predators or humans. Predator-caused mortality was largely confined to winter. There was little effect of wolf presence on adult deer mortality rates, and there was no difference in mortality between the two deer species relative to wolf-free or wolf-occupied sites. Although this study occurred early in wolf recovery in Washington, our results differ from those demonstrated for gray wolves in protected areas. Thus, we encourage further investigation of effects of direct predation by recolonizing large carnivores on prey in human-dominated landscapes.

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