Dataset: The implications of intraspecific trait variation from fish sampled in Rhode Island salt ponds from June to October 2018

Study system
We conducted this study within six coastal lagoons on the southern shore of Rhode Island: Green Hill (GH) Pond, Ninigret Pond (NP), Point Judith (PJ) Pond, Potter Pond (PP), Quonochontaug Pond (QP), and Winnapaug Pond (WP; Fig. S1.1). The fish communities in these ponds comprise mostly marine species, as all ponds are connected to the ocean via a breach way and recruits settle via larval dispersal. We focused on trait variation within and across species in 13 fish functional traits which represent three important functional roles: (1) energy acquisition, (2) locomotion, and (3) nutrient recycling (Villéger et al. 2017). We chose to examine fish communities, as they have been well studied in the functional trait literature, offering a comprehensive understanding of the functional roles fish provide and functionally meaningful traits to measure (Dumay et al. 2004, Mason et al. 2007, Villéger et al. 2010, 2017, Albouy et al. 2011, Stuart-Smith et al. 2013, Mouillot et al. 2013, Yeager et al. 2017, McLean et al. 2019).

Fish community collections
We sampled the six coastal pond fish communities monthly from June to October 2018 via 150-foot beach seine surveys in collaboration with the Rhode Island Department of Environmental Management. We targeted 38 species which accounted for 99.4% of total abundance across the surveys. We aimed to collect 20 individuals per species evenly distributed across their size range based on past survey data. Once collected from the seine net, fish were either transferred into seawater containers for excretion incubations or euthanized immediately via a seawater-clove oil (Eugenol extract, Syzygium aromaticum) mixture (IACUC protocol #: 18-0622R). Euthanized fish were held on ice before returning to the lab for morphometric analysis. We collected a total of 708 fish across 39 species and 26 families. We analyzed a subset of 200 fish for nutrient recycling traits, resulting in an average of 18.63 + 2.6 fish per species for energy acquisition and locomotion traits and an average of 7.48 + 0.91 fish per family for nutrient recycling traits.

Energy acquisition and locomotion traits
We took a series of five photos for each fish: (i) lateral full body, (ii) lateral head, (iii) lateral head with mouth protruded, (iv) ventral full body, and (v) anterior with mouth open, all with a ruler in shot for length standardization (Fig. S2.1a-e). Using ImageJ analysis, we measured 15 morphometrics which was used to calculate five energy acquisition traits: (oral gape surface, oral gape shape, oral gape position, protrusion, eye size) and five locomotion traits: (eye position, body transverse surface, body transverse shape, pectoral fin position, caudal peduncle throttling) (Table 1; Albouy et al. 2011). These continuous functional trait measurements have been commonly used in morphological studies on fishes and are connected to diet or movement (Sibbing and Nagelkerke 2000, Dumay et al. 2004, Mason et al. 2007, Villéger et al. 2010).

Nutrient recycling traits
We conducted excretion incubations for nutrient recycling traits, targeting 27 fish families (N = 1-3 species per family), which accounted for 99.7% of total abundance across the survey. Within each family, we targeted 10 individuals evenly distributed across their size range. Following the removal from the seine net each individual fish was placed directly into a 3L sterile plastic bag of seawater taken from the site before collection. Two 60mL 0.7 μm filtered water samples were taken from each plastic bag directly before and after each incubation trial, resulting in a pre-and post-incubation water sample for both N and P concentrations. Water samples were placed on ice and frozen immediately once returning from the field and kept in a -20°C freezer until processing. Each incubation lasted 30 minutes with bags placed in a larger cooler to ensure minimal stress. After incubations, fish were euthanized with a seawater-clove oil mixture. 

We analyzed all water samples for concentrations of ammonium (NH4+) and phosphate (PO43-) using two spectra-photometric assays of phenolhypochlorite (Solórzano 1969) and molybdenum blue (Murphy and Riley 1962) methods as modified by (Whiles et al. 2009). We calculated the difference between pre-and post-incubation water samples for both N and P concentrations to quantify the N and P contribution for each fish, (Fig. S2.1f-g). Lastly, we took the ratio of change of N to P for each fish to calculate the N:P functional trait.

All references to figures and tables are from Yeager, M. E. and A.R. Hughes. The implications of intraspecific trait variation for functional diversity. Diversity and Distributions. In Review.