Data from: Resource partitioning among pelagic predators remains stable despite annual variability in diet composition
Data files
Mar 21, 2025 version files 3.40 MB
-
hms_predator_depths.csv
2.92 KB
-
hms_predator_lengths_subset.csv
186.57 KB
-
hms_prey_lengths_subset.csv
591.57 KB
-
hms_prey_taxonomy.csv
11.83 KB
-
hms_prey_withTraits.csv
2.55 MB
-
README.md
5.28 KB
-
spMatrix_0.025_familyAggyes_1998_2018.rds
40.51 KB
-
sppHulls.rds
1.90 KB
Abstract
Diet data are critical for describing resource use and partitioning among competitors. However, timeseries of diet data needed to properly assess variability in resource use and partitioning are limited, especially in pelagic (open ocean) ecosystems where predators and prey make broad use of horizontal and vertical habitats.
We examined a diet timeseries spanning two decades (1998-2018), consisting of 2,749 stomachs from ten pelagic predators in the southern California Current Ecosystem (SCCE): albacore tuna (Thunnus alalunga), Pacific bluefin tuna (Thunnus orientalis), swordfish (Xiphias gladius), blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), common thresher shark (Alopias vulpinus), bigeye thresher shark (Alopias superciliosus), short-beaked common dolphin (Delphinus delphis), long-beaked common dolphin (Delphinus capensis), and northern right whale dolphin (Lissodelphis borealis). We examined feeding habits with respect to prey taxonomy, length, vertical habitat, and horizontal habitat.
From 1998-2015, each predator exhibited diet variability but maintained consistent resource partitioning with the other predators. Across years, the diets of predators feeding mostly on shallow-living prey (<200 m) were more variable than those feeding on deeper-dwelling prey (>200 m).
Following increased abundance of northern anchovy (Engraulis mordax) starting in 2016, the ecological niches of bluefin tuna and swordfish converged. Both predators fed more heavily on northern anchovy and other prey that occupy shallow nearshore habitats.
Changes in resource availability likely varied with depth across our time series. We show that pelagic predators can maintain resource partitioning under a wide range of conditions. However, we also observed that drastic changes in resource availability can alter the degree of niche partitioning among competitors, providing new perspectives on the flexibility of predator niches. As climate change continues to alter food webs, understanding how predators forage will be essential for anticipating changes to pelagic ecosystem structure and services.
https://doi.org/10.5061/dryad.wpzgmsc05
Description of the data and file structure
We examined a diet timeseries spanning two decades (1998-2018), consisting of 2,749 stomachs from ten pelagic predators in the southern California Current Ecosystem (SCCE): albacore tuna (Thunnus alalunga), Pacific bluefin tuna (Thunnus orientalis), swordfish (Xiphias gladius), blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), common thresher shark (Alopias vulpinus), bigeye thresher shark (Alopias superciliosus), short-beaked common dolphin (Delphinus delphis), long-beaked common dolphin (Delphinus capensis), and northern right whale dolphin (Lissodelphis borealis). We examined feeding habits with respect to prey taxonomy, length, vertical habitat, and horizontal habitat.
Intact and partial remains of prey items (e.g., fish bones, cephalopod beaks, crustacean appendages) were identified to the finest possible taxonomic resolution using published keys. Due to variable states of prey digestion within stomachs and among predator taxa, prey were rarely weighed, and all analyses are based on prey abundance. Lengths were measured for fresh and partially digested prey when possible and reported in mm as standard or fork length for fishes, mantle length for cephalopods, and total length for crustaceans. Whole lengths from partial remains (teleost vertebrae, cephalopod beaks) were estimated using published regressions
Files and variables
File: hms_prey_taxonomy.csv
Description:
Variables
- Prey_LPT: Prey identification to lowest taxonomic level possible
- Prey_Kingdom: Kingdom
- Prey_Phylum: Phylum
- Prey_Class: Class
- Prey_Order: Order
- Prey_Family: Family
- Prey_Genus: Genus
File: hms_predator_lengths_subset.csv
Description:
Variables
- Predator_ID: Unique identifier
- Predator_Species: Species
- Predator_Measurement: Length type (e.g. eye fork length, total length)
- Predator_Length: Length in cm
- Year: Year of collection
- Region: Region of collection
- Prey_N: Number of prey
File: sppHulls.rds
Description: Polygons covering collection locations
File: spMatrix_0.025_familyAggyes_1998_2018.rds
Description: Species matrixes for multivariate analyses, generated by code in public repo
File: hms_predator_depths.csv
Description:
Variables
- Predator_Species: Species
- region: Region of study
- startYr: Earliest year of study
- endYr: Last year of study
- pred_max_depth: Maximum depth of predator if available
- pred_max_depth_day: Daytime maximum depth
- pred_max_depth_night: Nighttime maximum depth
- pred_depth_mode_day: Daytime modal depth if available
- pred_depth_mode_night: Nighttime modal depth if available
- pred_depth_mean_day: Daytime mean depth if available
- pred_depth_mean_night: Nighttime mean depth if available
- diel_foraging: Times of day when foraging has been recorded
- references.depth: Citations for depth information
- doi.depth: DOI for citations
- references.diel.foraging: Citations for diel foraging behavior
- doi.diel.foraging: DOI for citations
- notes: Any helpful notes
File: hms_prey_lengths_subset.csv
Description:
Variables
- Predator_ID: Unique predator ID
- Prey_LPT: Prey identification to lowest taxonomic level possible
- Prey_Length: Prey length in mm
- group: Prey type
- Year: Year of collection
- Prey_Measurement: Measurement type (mantle length, standard length, total length, fork length)
- Predator_Species: Species of predator
- lenMat: Length at maturity
- life_stage: Assumed life stage based on length at maturity
File: hms_prey_withTraits.csv
Description:
Variables
- Prey_LPT: Prey identification to lowest taxonomic level possible
- Predator_ID: Unique predator identifier
- Prey_ID: Unique prey identifier
- Prey_N: Number of prey
- Predator_Species: Species of predator
- Predator_Measurement: Type of predators measurement (e.g. eye fork length, total length)
- Predator_Length: Length in cm
- Year: Year of collection
- Region: Region of collection
- Prey_Kingdom: Kingdom
- Prey_Phylum: Phylum
- Prey_Class: Class
- Prey_Order: Order
- Prey_Family: Family
- Prey_Genus: Genus
- life_stage_final: Assumed prey life stage
- species_lifestage: Life stage of prey species if available
- genus_lifestage: Life stage of prey genus if available
- family_lifestage: Life stage of prey family if species/genus not available
- depth_mode_day: Prey depth mode daytime if available from literature
- depth_mode_night: Prey depth mode nighttime if available from literature
- vert_habitat: Final vertical habitat classification
- inOff_habitat: Final inshore/offshore habitat classification
Code/software
All analyses are run in R. Public repo of code is available at https://github.com/barbmuhling/predatorDietsPublic
Access information
Other publicly accessible locations of the data:
- None
Data was derived from the following sources:
- Original analyses of predator gut contents