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9-7-2018 The Assemblage Structure and Trophic Ecology of a Deep-Pelagic Fish Family (Platytroctidae) in the Gulf of Mexico Michael Novotny Nova Southeastern University, [email protected]

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NSUWorks Citation Michael Novotny. 2018. The Assemblage Structure and Trophic Ecology of a Deep-Pelagic Fish Family (Platytroctidae) in the Gulf of Mexico. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (486) https://nsuworks.nova.edu/occ_stuetd/486.

This Thesis is brought to you by the HCNSO Student Work at NSUWorks. It has been accepted for inclusion in HCNSO Student Theses and Dissertations by an authorized administrator of NSUWorks. For more information, please contact [email protected]. Thesis of Michael Novotny

Submitted in Partial Fulfillment of the Requirements for the Degree of

Master of Science M.S. Marine Environmental Sciences

Nova Southeastern University Halmos College of Natural Sciences and Oceanography

September 2018

Approved: Thesis Committee

Major Professor: Tracey Sutton

Committee Member: Tamara Frank

Committee Member: Jon Moore

This thesis is available at NSUWorks: https://nsuworks.nova.edu/occ_stuetd/486

HALMOS COLLEGE OF NATURAL SCIENCES AND OCEANOGRAPHY

The Assemblage Structure and Trophic Ecology of a Deep-Pelagic Fish Family (Platytroctidae) in the Gulf of Mexico

Michael Novotny

Submitted to the Faculty of Halmos College of Natural Sciences and Oceanography in partial fulfillment of the requirements for the degree of Master of Science with a specialty in:

Marine Environmental Science

Nova Southeastern University

September 2018 Table of Contents

Acknowledgments...... 2 Abstract ...... 3 List of Tables ...... 4 List of Figures ...... 5 Introduction ...... 6 Methods ...... 10 Sampling Methods ...... 10 Specimen Processing and Gut Content Analysis ...... 12 Data analysis ...... 13 Results ...... 14 Catch Data ...... 14 Sex Ratio ...... 19 Dietary Analysis ...... 22 Barbantus curvifrons ...... 23 Maulisia microlepis ...... 24 Mentodus facilis ...... 25 Mentodus mesalirus ...... 26 Platytroctes apus ...... 27 Discussion ...... 29 Assemblage Composition ...... 29 Vertical Distribution ...... 30 Sex Ratio ...... 31 Dietary Habits ...... 32 Barbantus curvifrons ...... 32 Maulisia microlepis ...... 33 Mentodus facilis ...... 34 Mentodus mesalirus ...... 35 Platytroctes apus ...... 35 Summary ...... 36 References ...... 37 Appendix A ...... 43 Appendix B ...... 44 Appendix C ...... 45 Appendix D ...... 61 Acknowledgments

I would like to express my gratitude to everyone who helped with this thesis. Dr. Tracey Sutton, my advisor, was instrumental in the process and I would not be the scientist I am today without his guidance. Thank you for giving me the opportunity to become part of the lab, the endless support, and for your unique motivation over the course of this project. I would also like to thank my committee members, Dr. Tamara Frank and Dr. Jon Moore for their valuable insight throughout my graduate journey, this thesis would be far less without your guidance. Thank you, April Cook, for your guidance in handling and organizing such an extensive data set. I would also like to thank my labmates in the Oceanic Ecology Lab for the laughs and memories we shared, you truly became my second family. I would also like to thank my family for the love and support they have given, and most importantly I would like to thank my wife, Brittney, for her sacrifices, encouragement, and unfailing support during the course of my studies.

The Assemblage Structure and Trophic Ecology of a Deep-Pelagic Fish Family (Platytroctidae) in the Gulf of Mexico

Abstract

Members of the family Platytroctidae (tubeshoulders) are found throughout the meso- and bathypelagic waters of the World Ocean. Due to the lack of specimens collected globally, this taxon has received little attention, despite recent evidence suggesting its predominance in the bathypelagic biome. Prior to this study, only four species had been reported in the Gulf of Mexico’s (GoM) highly diverse deep-pelagic ecosystem. An extensive meso- and bathypelagic trawl series in the GoM allowed a detailed examination of this family, which included analyses of species composition, abundance, vertical distribution, sex ratios, and trophic ecology. A total of 16 species were collected, which included 12 new records for the GoM. The five most-abundant species collected were Mentodus facilis, Platytroctes apus, Barbantus curvifrons, Mentodus mesalirus, and Maulisia microlepis. All platytroctids were collected from tows that extended below 700 m. Mentodus facilis was the only species that significantly differed from the expected 1:1 sex ratio (p<<0.05) and strongly favored females. Gut content analysis revealed that platytroctids are zooplanktivores, consuming a wide variety of prey, such as gelatinous taxa, chaetognaths, copepods, euphausiids, ostracods, and occasionally cephalopods. The diet of Platytroctes apus indicated crustacean zooplanktivory primarily consisting of copepods and ostracods. Mentodus mesalirus and Maulisia microlepis heavily consumed gelatinous zooplankton. Mentodus facilis and Barbantus curvifrons had a more varied diet consuming chaetognaths, copepods, and ostracods, with M. facilis exhibiting a slightly greater reliance on ostracods and gelatinous prey. This study represents the first investigation into the diet of this fish family and adds to the sparse community data of the bathypelagic zone by identifying alternative nutrient pathways (e.g., the fish-jelly link) that connect the deep and upper oceanic ecosystems.

Keywords: Platytroctidae, Bathypelagic, Feeding habits, Gelatinous zooplankton, Range extensions.

List of Tables

Table 1. Pisces cruises conducted as part of the 2010-2011 ONSAP………………….. 11

Table 2. Standardized abundances of the top 20 fish families collected below 800 m depth using LMT gear in the GoM. 15

Table 3. Total platytroctids caught during the 2010-2011 ONSAP Pisces cruise series. 16

Table 4. Residual table from Crosstabulation Analysis of standardized abundances for deep day and night trawls. 18

Table 5. The sex ratios of the five most abundant platytroctid species captured during the 2010-2011 Pisces cruise series. 19

Table 6. Counts, size ranges, mean standard length, range of wet weights, and mean wet weight of examined platytroctids. 21

Table 7. The percentage of empty stomachs, empty intestines, and total vacuity for the most abundant platytroctid species collected in the GoM from the 2010-2011 Pisces cruise series. 22

Table 8. Feeding incidences during daylight and nighttime for the most abundant platytroctids collected in the GoM from the 2010-2011 Pisces cruise series. 22

Table 9. Summary of dietary indexes from Barbantus curvifrons, Maulisia microlepis, Mentodus facilis, Mentodus mesalirus, and Platytroctes apus. 28

List of Figures

Figure 1. Holtbyrnia innesi showcasing some prominent platytroctid features. 9

Figure 2. NOAA FRV Pisces sampling locations during the 2010-2011 ONSAP in the GoM. 11

Figure 3. Standardized abundances of the dominant platytroctids captured during shallow and deep tows. 17

Figure 4. Standardized abundances from deep day and deep night tows of the dominant platytroctid species. 18

Figure 5. Size distributions by sex of the five most abundant platytroctid species. 20

Figure 6. Numerical percentage and percent occurrence for prey types consumed by Barbantus curvifrons. 23

Figure 7. Numerical percentage and percent occurrence for prey types consumed by Maulisia microlepis. 24

Figure 8. Numerical percentage and percent occurrence for prey type consumed by Mentodus facilis. 25

Figure 9. Numerical percentage and percent occurrence for prey types consumed by Mentodu mesalirus. 26

Figure 10. Numerical percentage and percent occurrence for prey types consumed by Platytroctes apus. 27

1. Introduction

The deep-sea environment is the largest living space on Earth, covering approximately 68% of the earth’s surface and constituting almost 92% of the total volume of Earth’s oceans (Angel 1997; Haedrich 1997; Robison 2004). The deep sea includes depths from approximately 200 m to the ocean floor. The vast habitat of the deep sea is subdivided primarily by depth of sunlight penetration, and by the associated fauna. The first zone of the deep sea is the mesopelagic, extending from 200 m to 1000 m depth. Trace amounts of light reach the mesopelagic depths, resulting in disphotic conditions. The low- light conditions allow for the fauna to differentiate diurnal and nocturnal cycles, the stimulus for diel vertical migration, but not enough for photosynthesis to occur. Below the depths of the mesopelagic and extending to the benthic boundary layer lies the completely aphotic bathypelagic zone. Evidence for the continued subdivision of the bathypelagic into the abyssopelagic zone is limited and not universally accepted (Angel 1997; Sutton 2013). For the purposes of this study and of discussion the abyssopelagic is included in the bathypelagic zone.

Many extreme conditions are present in the deep sea. As depth increases, downwelling solar radiation diminishes, temperatures approach freezing, seasonal variability patterns decline, and pressure increases by approximately one atmosphere every 10 m, resulting in pressures exceeding 100 atmospheres in the bathypelagic zone (Idyll 1976; Cocker 1978). Deep-sea organisms have evolved many unique adaptations to survive in this extreme environment. Olfactory and mechanosensory systems are often greatly increased to account for low-light conditions, dense muscle tissue is replaced with watery tissues, and low metabolic rates contribute to slow locomotion (Cocker 1978; Childress 1995). Morphological adaptations exhibited by bathypelagic fishes include a reduction in relative eye size, reduced skeletal ossification, loss of photophores, replacement of reflective silver pigmentation with black, brown or red pigment, and loss or reduction of swim bladders (Marshall 1979). In the mesopelagic, bioluminescence is prevalent amongst many of the taxa, with at least 90% of its inhabitants producing light (Widder 2010). Many of the vertically migrating taxa found in the upper mesopelagic exhibit silver reflective pigmentation and

6 possess large ventral photophores (Denton et al., 1985). Fishes of the lower mesopelagic zone begin exhibiting adaptations to a darker environment, such as darker pigmentation, decrease in muscular density, and a declined metabolic rate, all of which continue to be exhibited in the bathypelagic zone (Marshall 1954; Childress, 1995; Salvanes & Kristoffersen, 2001). The bathypelagic zone occupies 7.5 times the total volume of the terrestrial environment and contains over 60% of the World Ocean, making the bathypelagic the largest environment on Earth (Herring 2002). Despite the enormity of the bathypelagic system, relatively little progress has been made towards describing its ecology. The scarcity of knowledge of the bathypelagic zone is primarily related to two reasons. First, primary production within surface and coastal waters supports most of the commercially important species, leading to more scientific exploration of these habitats than the deeper regions. Second, exploration into the bathypelagic zone is logistically challenging. The bathypelagic zone embodies an enormous ecosystem that is costly and time-consuming to study, in addition to being difficult to access. However, recent evidence has indicated bathypelagic fauna may play a significant role in the vertical and horizontal transformation and utilization of energy and nutrients, thereby connecting the productivity of the upper ocean to the communities of the deep seafloor (Drazen and Sutton, 2017). The deep-pelagic habitat is resource-poor in comparison to shallow-water environments. Due to decreased food abundance, previous studies argued that the diets of deep-sea fishes should be more generalized (Gage and Tyler, 1991). However, current diet analyses of mesopelagic fishes have shown specialization and niche partitioning among the deep-sea assemblages (Ebeling and Cailliet, 1974; Hopkins and Gartner, 1992). While trophic studies of mesopelagic and demersal fauna are fairly prevalent in the field of deep- sea research, the ecological links between the deep-pelagic and bathyal communities are just beginning to be understood (Hopkins et al., 1996; Drazen and Sutton, 2017). In the deep pelagial, zooplanktivory is the most common feeding strategy among fishes. The zooplanktivore feeding guild is organized into two subguilds, crustacean zooplanktivory and soft-bodied zooplanktivory (Gartner et al., 1997). Crustacean zooplanktivores generally possess numerous fine teeth and long gill rakers. Prey items of crustacean zooplanktivores are predominantly copepods and ostracods (Flock and

Hopkins, 1992; Hopkins and Gartner, 1992; Hopkins et al., 1996; Hopkins and Baird, 1985; Burghart et al., 2010;). Predators of soft-bodied zooplankton (i.e. gelatinous forms), such as bathylagid and alepocephalid fishes, have characteristics such as large eyes, a small gape, numerous and very fine teeth, grinding structures at the back of the throat, and a long, coiled intestine (Balanov et al., 1995; Beamish et al., 1999). Several other members of the soft-body zooplanktivory subguild have larger mouths, with or without a uniserial row of small teeth, used for biting off small chunks from the gelatinous prey (Gartner and Musick, 1989). The ecological role of gelatinous zooplankton in deep-sea trophic ecology is largely unknown (Arai, 2005). Reported estimates of these soft-bodied taxa from stomach contents may be artificially low due to rapid digestion and low detection success(Purcell and Arai, 2001; Arai, 2005). However, these large, complex gelatinous fauna may be capable of constituting one-fourth of the total pelagic biomass and can dominate the second and third trophic levels in some areas (Harbison et al., 1977; Robison, 2004; Robison et al., 2010). Historically considered a trophic dead end, the “jelly web” now appears to be an important pathway in some regions (Robison, 2004). Sutton et al. (2008) found that the biomasses of three fish families known or assumed to be gelativorous (i.e. Bathylagidae, Melamphaidae, and Platytroctidae) were ranked within the top five of 58 fish families sampled across the northern Mid-Atlantic Ridge, suggesting that gelativory may be a main trophic mode in the bathypelagic zone. The family Platytroctidae, previously referred to as Searsidae, contains 39 species in 13 genera worldwide (Nelson et al., 2016). Species inhabit mesopelagic to bathypelagic depths from the high latitudes to the tropics (Matsui and Rosenblatt, 1987). Platytroctids possess a relatively large, elongate body, large head and eyes, watery body tissues, a pharyngeal structure (crumenal organ) that handles or stores food items, and black or brown coloration (Parr, 1960; Lavoué et al., 2008). The large eyes contain a well- developed lens and a notable aphakic space ideal for detecting and localizing point sources of light (Warrant and Locket, 2004). The main synapomorphy of this family is the shoulder organ, or postcleithral gland, which contains a blue-green luminous fluid (Figure 1). This structure is found in the shoulder girdle area between the lateral line and the pectoral fin- base. The bioluminescent cellular fluid is released via a small black tube supported by a

8 modified scale and is thought to disorient predators, allowing for escape (Parr, 1951; Nicol, 1958; Herring, 1972).

Aphakic space Postcleithral gland

Figure 1. The platytroctid Holtbyrnia innesi showcasing the prominent features of the large eye with aphakic space and the unique postcleithral gland. Photo taken by Danté Fenolio.

The systematic placement of the Platytroctidae is a contentious topic. The family has been placed in at least two different suborders, three different orders, and two different superorders. However, the sister family has consistently been the Alepocephalidae (Nelson et al., 2016). Recent molecular evidence places the Platytroctidae, along with the Alepocephalidae and Bathylaconidae, within the order Alepocephaliformes, and further suggests, that this order should be removed from the Euteleostei and placed within Otocephala (Lavoué et al., 2008; Poulsen et al., 2009). An extensive bathypelagic trawl series in the northern Gulf of Mexico allowed for a detailed examination of the fish family Platytroctidae, including analyses of species composition, abundance, distribution, sex ratios and trophic ecology. This study represents the most complete ecological assessment of this fish family to date, including the first investigation of platytroctid trophic ecology.

2. Methods

2.1. Sampling Methods

Seven surveys were conducted in the northern GoM from December of 2010 through September 2011 as part of the NOAA-supported Natural Resource Damage Assessment (NRDA) after the Deepwater Horizon Oil Spill (DWHOS), which lasted from April to September 2010. The Offshore Nekton Sampling and Analysis Program (ONSAP) was established to survey the pelagic waters of the GoM to determine the composition, abundance, and distribution of the fauna that were potentially affected by the DWHOS. The ONSAP conducted sampling utilizing two research vessels, the M/V Meg Skansi and the NOAA FRV Pisces. This project incorporates specimens collected from the Pisces cruise series. A summary of the sampling dates, net types, and net sizes utilized during the Pisces series can be found in Table 1. The surveys aboard the NOAA FRV Pisces utilized various large midwater trawls (LMT), including a high-speed rope trawl (HSRT), an International Young Gadoid Pelagic Trawl (IYGPT), and a modified Irish herring trawl (IHT). All LMTs had a larger mesh at the mouth, which tapered to a smaller mesh size at the cod end. For example, the IHT had an effective mouth area of 165.47 m2 and a graded-mesh net from 3.2 m to 5 cm. The large pelagic nets used during the Pisces cruise series were non-closing nets, and therefore discrete-depth intervals could not be sampled. Sampling occurred during all seasons, from December 2010-September 2011, with each survey lasting approximately three weeks. A total of 17 stations were sampled across the northern GoM, most of which were seaward of the 1000-m isobath (Figure 2). Each station was sampled obliquely, with “shallow” and “deep” deployments conducted during both day and night at each station (i.e. four deployments per station, conducted within 24 h). The “shallow” deployments fished from the surface to less than 800 m, generally targeting a depth of approximately 700 m. The “deep” deployments exceeded 800 m depth and generally fished from the surface to 1300- 1500 m depth. All trawl deployments began at least one hour after sunrise and one hour after sunset to avoid periods of active vertical migration. A total of 171 trawls were conducted, with 84 considered shallow and 87 considered deep tows. All specimens were either frozen or stored in a 10% formalin solution until they could be processed in lab.

In addition to the initial sample processing that occurred at sea, fish identification and quantitative analysis of fish specimens were conducted by members of the Oceanic Ecology Laboratory at the Nova Southeastern University in Dania Beach, Florida. Once identified to the lowest possible taxonomic level, the standard length (in millimeters) and species weight (in grams) were recorded.

Table 1. Pisces cruises conducted as part of the 2010-2011 ONSAP: ship name, cruise number, dates, net type, and size. Effective mouth area (EMA) is the fishing circle in front of the 80-cm mesh section for each net.

Vessel Cruise Dates Net type Net size number NOAA Ship Pisces PC8 12/1/10-12/20/10 HSRT 333.64 m2 EMA

NOAA Ship Pisces PC9 3/22/111-4/11/11 HSRT 333.64 m2 EMA IYGPT 171.3 m2 EMA

NOAA Ship Pisces PC10 6/23/11-7/13/11 IHT 165.47 m2 EMA

NOAA Ship Pisces PC12 9/8/11-9/27/11 IHT 165.47 m2 EMA

Figure 2. Stations sampled from the FRV Pisces as part of the 2010-2011 ONSAP in the GoM. Stations are colored based on the number of times sampled. The orange line indicates the 1000-m isobath.

2.2. Specimen Processing and Gut Content Analysis

Platytroctid species that contributed more than 10% of the overall abundance of platytroctid catches from all trawls were included in the trophic component of this study. Individuals of the targeted species were measured to the nearest millimeter standard length (SL), blotted dry, and weighed to the nearest 0.01g. Specimens were then placed in a large petri dish or tray for dissection. A transverse cut was made through the isthmus directly behind the posterior edge of the operculum, followed by a shallow incision along the ventral surface of the fish, from the transverse cut to the anus. Separation and removal of the gastrointestinal tract was achieved via a cut through the esophagus. The digestive tract and all internal organs were removed and stored in a 70% ethanol: water mixture. The stomach was separated from the intestines by a cut just anterior to the junction of the pyloric caeca and then graded according to fullness. This subjective stomach fullness coefficient was based on a visual assessment of the stomach and utilized a scale of zero to five, with zero being empty and five being fully extended. Esophageal content was excluded due to possible net feeding events. Prey items were identified to the lowest possible taxonomic level, counted, and classified as one of three categories according to their degree of digestion: (1) freshly ingested/virtually intact, (2) partially digested but still recognizable, and (3) very digested/unrecognizable, only fragmentary parts remaining. Partially digested larger prey items were placed in vials containing 70% ethanol, while smaller, more digested items were affixed to a labeled glass slide for further identification. The slides were prepared with a glycerin:fuchsin-acid stain and examined under a compound microscope. Prey items were grouped into major categories for calculating indices of prey importance, such as ostracod, cnidarian, chaetognath, copepod, amphipod, euphausiid, teleost, cephalopod, unidentified crustacean, and unidentified material. For each species, two indices were calculated for all prey categories, percent occurrence (%O) and numerical percentage (%N). The percent occurrence index was calculated as the number of digestive tracts containing a specific prey type divided by the number of digestive tracts containing any food item.

𝑖푛푑𝑖푣𝑖푑푢푎푙푠 푤𝑖푡ℎ 푠푝푒푐𝑖푓𝑖푐 푝푟푒푦 𝑖 %O= 𝑖푛푑𝑖푣𝑖푑푢푎푙푠 푤𝑖푡ℎ 푝푟푒푦

Percent composition by number, or the numerical percentage, was determined by the total number of prey items of each prey type divided by the total number of all prey items.

푇표푡푎푙 푛푢푚푏푒푟 표푓 푠푝푒푐𝑖푓𝑖푐 푝푟푒푦 𝑖푡푒푚 𝑖 %N= 푁푢푚푏푒푟 표푓 푎푙푙 푝푟푒푦 𝑖푡푒푚푠

In addition to gut content analyses, sex was also documented via macroscopic visual determination for sex ratio purposes. Females were identified by the presence of mature ovaries containing eggs, while males were identified by the presence of mature testes. Immature or questionable individuals were categorized as undifferentiated. A Chi- Square Goodness of Fit test was used to determine if the calculated sex ratio of each species diverged from the expected 1:1 (male:female) ratio. Length-weight regressions were also produced for the targeted species (Appendix A).

2.3. Data analysis

Due to the non-opening/closing nature of the LMT’s, both “shallow” and “deep” trawl data were utilized to establish a bathypelagic ichthyofaunal inventory of the GoM. To compare the catch between the different trawling schemes, the number of fishes caught were standardized by dividing the numerical total per species by the summed tow durations to get the number of fishes caught per hour, respective of shallow/deep and day/night. The standardized catch from the shallow tows was used as an indicator of “contaminat” species in the deep tows. The standardized shallow species counts were subtracted from the standardized deep species counts to account for shallow-species contamination that occurred during deployment and retrieval while the deep net fished in non-targeted (shallower) depths. The species that remained were inferred to predominantly occur within the lower meso- and bathypelagic zones. Samples that possessed reliable depths and times were termed “quantitative”, whiles samples that possessed unreliable tow durations and unreliable depths were termed “non-quantitative” and were not used in abundance analyses. Platytroctid species occurrences in relationship to depth were analyzed utilizing a chi-squared goodness of fit analysis. The variation in species abundance with solar cycle at depth was analyzed utilizing a crosstabulation analysis.

3. Results

3.1. Catch Data

The ichthyofaunal species inventory of the GoM’s bathypelagic zone was subsequently grouped and summed by family. Upon sorting the families from highest to lowest standardized sums the Platytroctidae ranked as the fifth-most abundant fish family captured from bathypelagic depths (Table 2). The examination of species strictly captured from deep nets showed platytroctids as the most abundant family, comprising 20% of the individuals. A total of 499 platytroctids were collected utilizing the LMTs. Prior to the ONSAP there were four platytroctid species known in the GoM: Barbantus curvifrons, Holtbyrnia innesi, Mentodus facilis, and Platytroctes apus (McEachran and Fechhelm, 1998; Richards and Hartel, 2006). Sixteen species are reported here, including the four previously recognized GoM species (Table 3). The 16 identified species were represented by 420 individuals (Appendix D), the remaining 79 platytroctids being too damaged for species- level identification. Five species, Barbantus curvifrons (n = 48), Maulisia microlepis (n = 52), Mentodus facilis (n = 134), Mentodus mesalirus (n = 64), and Platytroctes apus (n = 55), comprised 84.05% of the catch data and were chosen for additional analyses. Known worldwide distributions of all identified species were mapped using the Ocean Biogeographic Information System (OBIS) mapper tool (Appendix C). The 58 quantitative shallow tows collected 18 platytroctids, from eight species: Holtbyrnia cyanocephala (n = 5), Holtbyrnia innesi (n = 4), Holtbyrnia macrops (n = 1), Maulisia argipalla (n = 3), Mentodus facilis (n = 1), Mentodus mesalirus (n = 1), Mentodus rostratus (n= 1), Searsia koefoedi (n = 2). Two of these species, Holtbyrnia cyanocephala and Mentodus rostratus, were caught only in shallow tows. A total of 379 platytroctids, from 14 species, were captured from 61 of the 63 quantitative deep tows.

Table 2. Standardized abundances of the top 20 fish families collected below 800 m depth using LMT gear in the GoM.

Rank Family Abundance Percent of Total Abundance (Fish/100hrs) 1 Sternoptychidae 691.2 20.57%

2 Myctophidae 465.4 13.85%

3 Alepisauridae 402.9 11.99%

4 Bathylagidae 207.7 6.18%

5 Platytroctidae 183.3 5.46%

6 Chiasmodontidae 174.4 5.19%

7 Gonostomatidae 154.1 4.58%

8 Giganturidae 152.3 4.53%

9 Nemichthyidae 121.8 3.62%

10 Melamphaidae 103.8 3.09%

11 Alepocephalidae 77.9 2.32%

12 Cetomimidae 74.7 2.22%

13 Serrivomeridae 57.6 1.71%

14 Stomiidae 45.3 1.35%

15 Paralepididae 37.8 1.12%

16 Linophrynidae 35.9 1.07%

17 Himantolophidae 23.5 0.70%

18 Anoplogastridae 21.1 0.63%

19 Melanocetidae 17.8 0.53%

20 Bathylaconidae 15.1 0.45%

Table 3. Total platytroctids caught during the 2010-2011 ONSAP Pisces cruise series. Species shown in bold were included in additional analyses. Previously reported GoM species are indicated by *

Lowest ID Counts Mentodus facilis* 134 Mentodus mesalirus 64 Platytroctes apus* 55 Maulisia microlepis 52 Barbantus curvifrons* 48 Maulisia spp. 31 Holtbyrnia innesi* 24 Unid. Platytroctidae 21 Holtbyrnia spp. 17 Maulisia argipalla 15 Mentodus spp. 10 Holtbyrnia cyanocephala 5 Mentodus crassus 5 Searsia koefoedi 5 Holtbyrnia macrops 4 Holtbyrnia anomala 3 Maulisia mauli 3 Maulisia acuticeps 1 Mentodus rostratus 1 Sagamichthys schnakenbecki 1 Total 499

The depth of capture and standardized abundance of the five most abundant platytroctid species are shown in Figure 3, while Figure 4 shows the standardized abundances of the top five species from the deep tows during both day and night. Three of the five platytroctid species subjected to further detailed examination were captured solely during deep tows. A chi-squared goodness of fit analysis confirmed Mentodus facilis (χ2=51.793, p<<0.05) and Mentodus mesalirus (χ2=28.821, p<<0.05) were captured at significantly greater abundances during the deep tows. Preforming a chi-square crosstabulation analysis on ‘deep’ abundance fluctuations with solar period showed Barbantus curvifrons and Mentodus facilis exhibited significant differences in abundance between sampling times, with B. curvifrons more abundant in the day trawls and M. facilis more abundant in the night trawls (Table 4).

30 Shallow (Less than 800m) Deep (greater than 800m)

20 Fish per Fish hrs 100

0 Barbantus Maulisia Mentodus Mentodus Platytroctes curvifrons microlepis facilis mesalirus apus

Figure 3. Standardized abundances of the dominant platytroctids captured during shallow and deep tows.

40 Deep (Greater than 800m) Day 30

Deep (Greater than 800m) Night Fish Fish per hrs 100 20

0 Barbantus Maulisia Mentodus Mentodus Platytroctes curvifrons microlepis facilis mesalirus apus

Figure 4. Standardized abundances of day/night deep tows of the dominant platytroctid species.

Table 4. Residual table from Crosstabulation Analysis of standardized abundances for deep day and night trawls. Residuals less than -2 indicate the occurrence of the species was less often than expected; while residuals greater than 2 indicate the occurrence of the species more often than expected. Species Deep Day Deep Night

Barbantus curvifrons 7.99419 -7.99963

Maulisia microlepis -0.93875 0.93939

Mentodus facilis -3.95111 3.95380

Mentodus mesalirus -1.48110 1.48211

Platytroctes apus 1.57213 -1.57320

3.2 Sex Ratio

Visible gonads (i.e. maturing or mature) were found in 267 of 283 specimens. A total of 101 were males and 166 were females; only 16 platytroctids were immature and gonads were not identified. The total number of individuals containing gonads and the sex ratios for all species are summarized in Table 5. The range of length and weight, as well as mean length and weight, was determined for males and females of all species (Table 6). Size distribution by sex is illustrated in Figure 5. Chi-square values were calculated to determine if the observed sex ratio of each species diverged from the expected ratio of 1:1 (male:female). Mentodus facilis was the only species that significantly diverged from the expected 1:1 sex ratio, with a male:female ratio of 1.0:2.8 (p<<0.05).

Table 2. The sex ratios (Male:Female) of the five most abundant platytroctid species captured during the 2010-2011 Pisces cruise series. Undifferentiated gonads are indicated by Undiff.

Number of Specimens Species Male Female Undiff. Total Sex χ2 P Ratio Barbantus curvifrons 18 19 1 41 1:1.06 0.027 0.869 Maulisia microlepis 10 11 1 22 1:1.10 0.048 0.827 Mentodus facilis 30 84 6 126 1:2.8 25.579 4.246×10-7 Mentodus mesalirus 28 31 0 61 1:1.11 0.153 0.696 Platytroctes apus 15 21 8 45 1:1.40 1.000 0.317

Barbantus curvifrons Maulisia microlepis 8 6 5 6 4 F F 4 3 M 2 2 M 1

0 0

No. Specimens of No. Specimens of

Standard Length (mm) Standard Length (mm)

Mentodus facilis Platytroctes apus 50 8 40 6 30 F F 4 20 M M 2 10

0 No. Specimens of 0

No. Specimens of

71-80 81-90

61-70 31-40 51-60 71-80 81-90

91-100

101-110 111-120 121-130 131-140 141-150

101-110 111-120 Standard Length (mm) Standard Length (mm)

Mentodus mesalirus 8 6 4 F 2 M

No. Specimens of

31-40 71-80 81-90

111-120 101-110 121-130 131-140 151-160 161-170 171-180 181-190 191-200 201-210 211-220 221-230 Standard Length (mm)

Figure 5. Size distributions by sex of selected species.

Table 6. Counts, size ranges (mm SL), mean standard length (SL), range of wet weights (g), and mean wet weight (g) of examined platytroctids. Standard length measured in mm and weight in grams.

Species N Range SL Mean SL Range Weight Mean Weight

Barbantus curvifrons

Male 18 60-111 89.22±13.77 1.53 - 11.06 5.79±2.74

Female 19 56–110 87.37±15.89 0.79 - 12.31 5.58±3.58

Maulisia microlepis

Male 10 165 – 215 186.60±13.14 33.68 - 90.84 53.98±16.29

Female 11 150 – 220 186.90±22.66 23.10 – 99.83 56.76±24.60

Mentodus facilis

Male 30 75 – 116 92.38±11.50 2.81 – 10.2 5.70±2.21

Female 84 40 – 114 90.70±13.02 0.39 – 13.12 5.60±2.34

Mentodus mesalirus

Male 28 124 – 220 183.07±24.32 11.09 – 102.14 53.24±24.97

Female 31 38 – 230 169.15±52.57 0.34 – 95.75 51.43±33.12

Platytroctes apus

Male 15 85 – 140 110.40±17.47 4.26 – 29.77 15.02±6.60

Female 21 71 – 148 116.90±21.89 3.3 – 37.62 19.27±10.52

3.3. Dietary Analysis

A total of 276 platytroctids were utilized for gut content analysis. The percentage of empty stomachs (PES), the percentage of empty intestines (PEI), and the percentage of completely empty digestive tracts (Total Vacuity) were calculated for each species (Table 7). Platytroctes apus had the lowest PES at 29.55%, but had the highest PEI at 59.09%. Barbantus curvifrons had the highest PES at 66.7% and Mentodus mesalirus had the lowest PEI at 21.57%. The remaining species had similar PES and PEI. Feeding incidence (FI) was determined as the percentage of specimens containing at least one prey item in the stomach. Feeding incidences were documented during both day and night in all species, and a Fisher’s Exact Test showed no significant differences between solar periods (Table 8).

Table 7. The percentage of empty stomachs (PES), empty intestines (PEI), and total vacuity for the most abundant platytroctid species collected in the GoM from the 2010-2011 Pisces cruise series.

Empty Species N PES (%) PEI (%) Total Vacuity (%) Stomachs Barbantus curvifrons 39 26 66.67 32.43 24.32 Maulisia microlepis 22 11 50.0 30.0 10.0 Mentodus facilis 115 64 55.65 33.04 22.32 Mentodus mesalirus 56 27 48.21 21.57 11.76 Platytroctes apus 44 13 29.55 59.09 25.0

Table 8. Feeding incidence (FI) during daylight and nighttime for the most abundant platytroctids collected in the GoM from the 2010-2011 Pisces cruise series. Numbers in parentheses indicate the number of examined individuals.

Species % FI Day % FI Night OR P Barbantus curvifrons 33.3 (27) 33.3 (12) 1 1.00 Maulisia microlepis 50.0 (8) 53.8 (13) 1.158 1.00 Mentodus facilis 41.1 (56) 45.8 (59) 1.208 0.7073 Mentodus mesalirus 47.8 (23) 54.5 (33) 1.303 0.7864 Platytroctes apus 60.9 (23) 81 (21) 2.670 0.1936

3.3.1. Barbantus curvifrons

A total of 48 Barbantus curvifrons were collected, 39 of which were dissected for dietary analysis. Positive stomachs (i.e. stomach containing at least one prey item) were found in 13 specimens, positive intestines in 25 specimens, eight fish had material in both, and nine had no material in either. This gave a PES of 66.67%, a PEI of 32.43%, and a total vacuity of 24.32% (Table 7). Barbantus curvifrons fed largely on chaetognaths, which dominated in numbers and frequency of occurrence (58%N and 80%O; Fig. 6). Secondary prey were copepods (24%N), ostracods (14%N), and occasionally cnidarians. Prey items identified to Copepoda occurred in half of the positive guts examined and the copepod genus Pleuromamma (9.3%N) was present in roughly one-quarter of positive guts analyzed. Ostracods occurred in almost half (43%O) of the positive guts examined. Cnidarian prey were the lowest component of the diet by both numbers (3.9%N) and occurrence (17%O). The majority of prey items were in a very advanced state of digestion. Barbantus curvifrons consumed an average of 3.33 prey items and a maximum of 16 prey items. Parasitism, as evident by helminth eggs, was observed in two individuals.

Barbantus curvifrons

Cnidaria, 3.9(17) Copepod, 14.7(50)

Pleuromamma spp, 9.3(23)

Ostracod, 14(43) Chaetognath, 58(80)

Figure 6. Abundance (%N) and percent occurrence (%O) for prey types consumed by B. curvifrons. Pie slices represent %N and numbers in parentheses after prey items represent %O.

3.3.2. Maulisia microlepis

A total of 52 Maulisia microlepis were collected, 22 of which were dissected for dietary analysis. Positive stomachs were found in 11 specimens, positive intestines in 14 specimens, seven fish had material in both, and two fish had no material in either. This resulted in a PES of 50.0%, a PEI of 30.0%, and a total vacuity of 10.0% (Table 7). The guts of M. microlepis contained an average of 1.36 prey items and a maximum of four prey items. Gelatinous prey items dominated the diet of M. microlepis in both numbers and frequency of occurrence (57%N and 94.4%O; Fig. 7). Two individuals contained a single cephalopod (6.7%N and 11.11%O). Secondary prey included amphipods and copepods, together making up 23.7%N. Incidental prey, occurring only once, such as ostracods, chaetognaths and euphausiids, contributed minimal numbers and percent occurrence (3.3%N and 5.5%O). Parasitism, as evident by helminth eggs, was observed in nine individuals.

Maulisia microlepis Atolla wyvillei, 3.3(5.56) Cephalopoda, 6.7(11.11) Amphipod, 6.7(11.11) Euphausiid, 3.3(5.56)

Copepod, 16.7(22.22)

Pleuromamma spp., 3.3(5.56)

Ostracod, 3.3(5.56)

Cnidaria, 53.3(94.4) Chaetognath, 3.3(5.56)

Figure 7. Abundance (%N) and percent occurrence (%O) for prey types consumed by M. microlepis. Pie slices represent %N and numbers in parentheses after prey items represent %O.

3.3.3. Mentodus facilis

A total of 134 Mentodus facilis were collected, 115 of which were dissected for dietary analysis. Positive stomachs were found in 51 individuals, positive intestines in 75 specimens, 37 fish had material in both, and 27 had no material throughout the digestive track. This gave a PES of 55.65%, a PEI of 33.04%, and a total vacuity of 22.32% (Table 7). The guts of Mentodus facilis primarily contained chaetognaths, ostracods, and cnidarians (together 79%N; Fig. 8). Chaetognaths were the most abundant prey (36%N) but ranked third in occurrence (53%O). Ostracods followed in abundance (24%N) and ranked second in occurrence (60%O). Cnidarian tissue was third in abundance (19%N) but occurred in the most (64%O) digestive tracts. Secondary prey items consisted of unidentified copepods (7.6%N, 23%O), amphipods (3.8%N, 13%O), euphausiids (1.7%N, 5.7%O), and the copepods Oncaea spp. (1.4%N, 4.5%O), and Pleuromamma spp. (1%N, 2.3%O). A fish from the genus Cyclothone was also consumed as prey. The digestive tract of M. facilis contained an average of 2.51 prey items with a maximum of 12 prey items. Parasitism, from the presence of nematodes and eggs, was observed in 44 individuals.

Mentodus facilis Crustacean, 4.5(14.8) Oncaea spp., 1.4(4.5) Cyclothone spp., 0.3(1.1) Euphausiid, 1.7(5.7) Cnidaria, Copepod, 7.6(22.7) 19.4(63.6) Pleuromamma spp.,1.0(2.3) Amphipod, 3.8(12.5)

Ostracod, 23.8(60.2) Chaetognath, 36.3(53.4)

Figure 8. Abundance (%N) and percent occurrence (%O) for prey type consumed by M. facilis. Pie slices represent %N and numbers in parentheses after prey items represent %O.

3.3.4. Mentodus mesalirus

A total of 64 Mentodus mesalirus were collected, 56 of which were dissected for dietary analysis. Stomachs containing prey were found in 29 specimens, positive intestines were in 40 individuals, 22 fish had material in both, and nine had no material in either. This gave a PES of 48.21%, a PEI of 21.57%, and a total vacuity of 11.76% (Table 7). Mentodus mesalirus fed abundantly on cnidarian prey, which dominated both numbers and occurrence (71.8%N and 93.6%O; Fig. 9). The diet of one individual was complemented with a single cephalopod (1.6N% and 2%O). The average number of prey consumed by M. mesalirus was roughly one item and a maximum of four items; cnidarian material was often the only prey found in the digestive tract. Secondary prey items consisted of ostracods and copepods, together comprising 17.1%N. Chaetognaths and amphipods were consumed rarely and together contributed only 6.2%N. Nematodes and eggs were observed in 30 of the 47 individuals that contained digested material.

Mentodus mesalirus Crustacean, 3.1,(4.3) Cephalopoda, 1.6(2.1) Amphipod, 3.1(2.1) Copepod, 6.2(8.5)

Ostracod, 10.9(14.9)

Chaetognath, 3.1(4.2)

Cnidaria, 71.8(93.6)

Figure 9. Abundance (%N) and percent occurrence (%O) for prey types consumed by M. mesalirus. Pie slices represent %N and numbers in parentheses after prey items represent %O.

3.3.5. Platytroctes apus

A total of 55 Platytroctes apus were collected, 44 of which were dissected for dietary analysis. Positive stomachs were found in 31 individuals, positive intestines were in 18 specimens, 16 fish had material in both, and 11 had no material in either. This gave a PES of 29.55%, a PEI of 59.09%, and a total vacuity of 25.0% (Table 7). Platytroctes apus fed predominantly on copepods (47.6%N and 78.8%O; Fig. 10), complementing its diet with ostracods (21%N, 64%O) and chaetognaths (11%N, 36%O). The primary copepod prey item in both numbers (28%N) and occurrence (39%O) was from the genus Pleuromamma. Amphipods, cnidarians, and euphausiids were occasionally consumed (together comprising 18.6%N), with each taxon occurring roughly in ¼ of the positive digestive tracts. The average number of prey items contained in the digestive tracts of P. apus was 4.72 with a maximum of 26 prey items. Helminth eggs were observed in two of the 33 individuals that contained digested material.

Platytrocrtes apus Crustacean, 1.9(9.1) Cnidaria, 5.8(27.3) Euphausiid, 5.1(21.2) Copepod, 5.8(21.2) Chaetognath, 10.9(36.4) Calanoid, 10.3(27.3)

Ostracod, 20.5(63.6) Oncaea spp., 3.2(15.2)

Microsetella spp., 0.6(3.0)

Amphipod, 7.7(33.3) Pleuromamma spp., 28.2(39.4)

Figure 10. Abundance (%N) and percent occurrence (%O) for prey types consumed by P. apus. Pie slices represent %N and numbers in parentheses after prey items represent %O.

Table 9. Percent number (%N) and percent occurrence (%O) for prey items consumed by Barbantus curvifrons, Maulisia microlepis, Mentodus facilis, Mentodus mesalirus, and Platytroctes apus.

Barbantus curvifrons Maulisia microlepis Mentodus facilis Mentodus mesalirus Platytroctes apus Prey category %N %O %N %O %N %O %N %O %N %O Cephalopoda 6.7 11.11 1.6 2.0 Chaetognatha 58.0 80.0 3.3 5.56 36 53.0 3.1 4.0 11.0 36.0 Copepoda 15.0 50.0 17 22.22 7.6 23.0 6.3 9.0 5.8 21.0 Calanoida 10.0 27.0 Pleuromamma spp. 9.3 23.0 3.3 5.56 1 2.3 28.0 39.0

Oncaea spp 1.4 4.5 3.2 15.0 Microsetella spp. 0.6 3.0

Euphausid 3.3 5.56 1.7 5.7 5.1 21.0 Amphipod 6.7 11.11 3.8 13.0 3.1 2.0 7.7 33.0 Crustacea 4.5 15..0 3.1 4.0 1.9 9.0 Cyclothone spp. 0.3 1.1

Ostracoda 14.0 43.0 3.3 5.56 24 60.0 11.0 15.0 21.0 64.0 Cnidaria 3.9 17 53 94.44 19 64.0 69.0 94.0 5.8 27.0 Atolla wyvillei 3.3 5.56

4. Discussion

4.1. Assemblage Composition

The 2010-2011 ONSAP resulted in one of the most comprehensive midwater nekton trawl series ever conducted (Judkins et al. 2016). A robust inventory of the GoM’s upper bathypelagic zone was compiled from the 121 quantitative deployments aboard the FRV Pisces. Ranked fifth in ichthyofaunal abundance, the family Platytroctidae was a ubiquitous component of the bathypelagic GoM. The collection and identification of seven genera and 16 species represents approximately half of the Platytroctidae family, making the GoM a ‘hotspot’ for platytroctid biodiversity. In addition to Barbantus curvifrons, Holtbyrnia innesi, Mentodus facilis, and Platytroctes apus, the known platytroctid assemblage of the GoM now includes Holtbyrnia anomala, Holtbyrnia cyanocephala, Holtbyrnia macrops, Maulisia acuticeps, Maulisia argipalla, Maulisia mauli, Maulisia microlepis, Mentodus crassus, Mentodus mesalirus, Mentodus rostratus, Sagamichthys schnakenbecki, and Searsia koefoedi. The most abundant species in this study, Barbantus curvifrons, Maulisia microlepis, Mentodus facilis, Mentodus mesalirus, and Platytroctes apus comprised approximately 84% of the total number of platytroctid species collected. Holtbyrnia innesi, while previously known to be present in the GoM, was less abundant than two newly recorded species, comprising less than 10% of the platytroctid catch, and ranking sixth in abundance. The remaining species occurred rarely, often totaling less than five individuals. The abundance of platytroctids in the deep GoM is a trait shared with the bathypelagic depths of the northern Mid-Atlantic Ridge, where the biomass of platytroctids was among the top five bathypelagic fish families captured (Sutton et al., 2008). From the Mid- Atlantic Ridge Maulisia microlepis comprised approximately 60% of the platytroctid biomass with Holtbyrnia anomala and Normichthys operosus each contributing approximately 18% of the biomass (Sutton et al., 2008). As a major contributor to the bathypelagic zone, platytroctids may play a significant role in cycling carbon and nutrients through the bathypelagic.

4.2. Vertical Distribution

Platytroctids were collected from both shallow and deep deployments, though were significantly more abundant in the latter. Two rare species, Holtbyrnia cyanocephala (n = 5) and Mentodus rostratus (n = 1), were caught only in shallow tows. The recorded depth distribution for H. cyanocephala encompasses epi-, meso-, and bathypelagic waters (Quero et al. 1990). Mentodus rostratus has been documented well into the bathypelagic zone, with a depth distribution of 980–2100 m (Quero et al. 1990). The single M. rostratus collected in this study was from a trawl that fished from 0 – 707 m depth and was 53 mm SL. Whether this indicates a vertical range extension, a passive migration, or ontogenetic migration is unknown. The other shallow-captured species were also collected in deep deployments. The deep tows captured more than 95% of the collected platytroctids. The most abundant species in this study were captured in greater abundances, or solely, below 800 m, corroborating known depth distributions. Barbantus curvifrons is known from 800- 2000 m depths (Carter 2002). Maulisia microlepis has been recorded to have a wide depth range from 750-2300 m depth (Sutton et al., 2008). Mentodus facilis has been reported to inhabit the lower meso- to bathypelagic depths from 650–2000 m (Orrell and Hartel 2016). Mentodus mesalirus and Platytroctes apus have been repeatedly found within bathypelagic depths (Carter 2002; Orrell and Hartel 2016). Unlike the large gear types used in this study, deep-pelagic studies traditionally utilize standard rectangular midwater trawling gear. The smaller, standard gear often results in the occurrence of platytroctid species being documented from only a few specimens (Matsui and Rosenblatt, 1987; Sazonov and Miya, 1996; Fock et al., 2004; Sutton et al., 2010) due to active net avoidance, not low abundances (Sutton et al., 2008). The deep day/night catch rates for Maulisia microlepis, Mentodus mesalirus, and Platytroctes apus followed a classical convention of deep-sea ecology that bathypelagic fauna do not vertically migrate. Recent evidence has challenged this notion and revealed some bathypelagic fishes do undertake an active vertical migration into shallower waters (Cook et al. 2013). This previously unknown vector of connectivity suggests that generalizations about the deep-pelagic fauna may be oversimplified, and migration may occur in various bathypelagic taxa as Vinogradov's (1968) ‘ladder of migration’ suggested.

The deep day/night catch rates for Barbantus curvifrons and Mentodus facilis were significantly different. Barbantus curvifrons had a higher standardized abundance in deep day trawls compared to deep night trawls, whereas M. facilis had a higher standardized abundance in deep night deployments. The minimal representation in shallow nets underscores the lack of the typical diel vertical migration nature of these species, yet they may be migrating deeper into the bathypelagic zone. The differing day/night abundances of B. curvifrons and M. facilis is an interesting finding and additional sampling to even greater depths would be needed to conclusively determine the driver behind the differential catch rates.

4.3. Sex Ratio

The expected and most frequently observed sex ratio in fishes is 1:1. A significant departure from this 1:1 ratio in fishes is not common (Conover and Van Voorhees, 1990). Mentodus facilis was the only examined species that significantly departed from this ratio (p<<0.05) and strongly favored females. A divergence from a 1:1 sex ratio can be attributed to multiple factors, such as differential activity levels, mortality rates, growth rates, or spatial distributions amongst sexes (Clarke, 1983). A higher female ratio contributes to an increased egg production and biomass, and could increase the probability of males finding a mate (Herring, 2002). Females may promote sexual competition by having multiple mates and through postcopulatory mechanisms such as sperm storage, increases the quality and quantity of offspring (Evans and Magurran, 2000). This is the first study to investigate platytroctid sex ratios, so comparison with different locations and platytroctid species was not possible. Favoring one sex would seem problematic for a species that has no photophores to signal conspecifics and exhibits no evidence of sexual dimorphism, as is the case with M. facilis. In order to increase the probability of finding a mate, M. facilis may use its bioluminescent fluid to signal conspecifics in a mating display. Secreting luminescence in a courtship display is exhibited in cypridinid ostracods from the reef systems of the Caribbean Sea (Morin, 1986; Morin and Cohen, 1991; Cohen and Morin, 2003). The species-specific display occurs as a series of timed pulses of luminescence that are precisely spaced, spanning a few mm to many meters (Morin and Cohen, 2010).

4.4. Dietary Habits

A classic hypothesis regarding bathypelagic foraging strategies is that the dominant feeding behavior would be truly generalist (Gage and Tyler, 1991). Theoretically, foragers will target more energetically valuable prey when food densities are high, and when food abundance declines the diet of fishes should broaden (Hart, 1989). This hypothesis has been shown to be overly simplistic, as food partitioning has been repeatedly found to occur in the mesopelagic zone (Hopkins and Gartner 1992; Hopkins et al. 1994; Burghart et al. 2010; Carmo et al. 2015; Carrasson and Matallanas 1998). Generally, diets of midwater fishes can be divided into three major feeding guilds: zooplanktivores, which consume planktonic organisms such as copepods, ostracods, and amphipod; micronektonivores, which consume cephalopods and fishes; and generalist, which consume a wide variety of unrelated taxa (Gartner et al., 1997). These three major feeding guilds have been subdivided and further specialized, with Hopkins et al. (1996) establishing 15 guilds for the mesopelagic GoM. Rather than trending to more generalized diets, specialized feeding guilds replace the extreme specialists of the shallow-water habitats (Drazen and Sutton, 2017). The examination of five platytroctid species revealed a feeding strategy centered on zooplanktivory, not a feeding strategy of a true generalist. The diet of Platytroctes apus can further be categorized as consisting of small crustacean zooplankton, primarily copepods and ostracods. Mentodus mesalirus and Maulisia microlepis had a diet consisting of approximately 72% and 53% cnidarian prey, respectfully, and belong to a gelatinous zooplanktivore feeding guild. Barbantus curvifrons exhibited a diet of mainly non- crustacean invertebrate zooplankton (chaetognaths) and small crustaceans. Mentodus facilis exhibited a more generalist zooplanktivore diet consuming chaetognaths, copepods, ostracods, euphausiids, and gelatinous prey.

4.5.1. Barbantus curvifrons The diet of Barbantus curvifrons consisted primarily of chaetognaths, ostracods, and copepods (mainly calanoids, including the genus Pleuromamma), with a minimal contribution of cnidarians. Chaetognaths dominated the diet in both percent occurrence (80%) and percent number (58%). The actual frequency of ingestion and importance of chaetognaths to the diet of B. curvifrons is likely to be greater than reported due to

quantification methods. Chaetognaths were tallied by dividing the number of grasping spines by 13, which is the largest possible number possessed by any chaetognath species known from the GoM (McLelland 1989). Although this method ensures that prey items are not over-represented, it may inherently underrepresent prey, as chaetognath species from the GoM can have as few as three spines and individuals gain and loses their spines with age (McLelland, 1989). Chaetognaths are often important trophic mediators in many marine food webs and can dominate the biomass of midwater plankton tows, especially in the upper half of the bathypelagic zone (Bone et al. 1991; Robison et al. 2010). Within the Sargasso Sea, Eukrohnia fowleri and Caecosagitta macrocephala dominant the deep-water chaetognath species starting at 700 m depth. The abundance of E. fowleri starts to decline past 1250 m depth, while C. macrocephala continues to dominate till 2000 m depth (Pierrot-Bults, A.C., 1982). From the Caribbean Sea and surrounding waters C. macrocephala was the dominant bathypelagic species followed closley by E. fowleri (Michel, H.B., 1984). Both species have been documented to occur in the meso- to bathypelagic waters of the GoM and are the only two species of chaetognaths found to be bioluminescent (McLelland, 1989; Thuesen et al., 2010). Barbantus curvifrons possess eyes whose structure should allow them to locate point-sources of light (Warrant and Locket, 2004) to help target and consume these two chaetognath species.

4.5.2. Maulisia microlepis The diet of Maulisia microlepis consisted primarily of cnidarians, but also included squids, copepods, euphausiids, ostracods, amphipods, and chaetognaths. One individual contained a freshly ingested scyphozoan, Atolla wyvillei, and two individuals consumed a cephalopod. Cnidarian material was present in all specimens that contained digested material except for one individual, which consumed a cephalopod. Gelatinous prey is largely underrepresented in dietary data due to rapid digestion rates impeding numerical quantification techniques (Arai et al., 2003; Robison, 2004; Drazen and Sutton, 2017). In this study, the numerical representation of Cnidaria in the diet was counted as one individual any time a nematocyte was identified amongst digested material, regardless of how many nematocytes were found. Despite this limitation, cnidarian prey comprised 53% of all items identified in the gut contents of M. microlepis. The occurrence of crustaceans

(euphausiids, copepods, ostracods) and chaetognaths within the diet would seem to represent “snacking,” as each was documented once. Alepocephalid fishes, the sister group to the Platytroctidae, have a similar external anatomy, and species have been documented to perdate on gelatinous zooplankton and cephalopods (Moore et al. 2003; Jones and Breen 2013; Carrasson and Matallanas 1998). Due to the evolutionary relationship between these two families and the similar morphological and anatomical characteristics, the occurrence of cephalopods within the diet of a large bodied, large-gaped species of platytroctid was not completely unanticipated. The intestinal complexity of M. microlepis is indicative of a diet that is nutritionally poor. Large numbers (approximately 45) of pyloric caeca give way to a corkscrew shaped lower intestine designed to increase retention, digestion, and absorption of nutrient-poor food items (Wagner et al. 2009). Minimal teeth, a large gape capable of swallowing bulbous hydromedusa, an expansive stomach, and intestines designed to maximize digestion and absorption are suitable characteristics of a diet primarily consisting of soft- body prey and gelatinous taxa (Arai 2005).

4.5.3. Mentodus facilis Mentodus facilis fed abundantly on chaetognaths, ostracods, and cnidarians. The caveats of chaetognath and cnidarian underestimation in trophic studies are discussed above and continue to confound quantitative assessment. Chaetognaths were the most abundant prey item consumed and occurred in over half of the positive guts. Both ostracods and cnidarians occurred in over 60% of positive individuals and ranked second and third in abundance respectively. The diet of M. facilis was supplemented by a variety of additional taxa, including euphausiids, copepods (Pleuromamma spp. and Oncaea spp.), and amphipods. Amphipod remains were only observed in specimens that contained cnidarian material. Hyperiid amphipods have a well-documented association with cnidarians (Harbison et al. 1977; Riascos et al. 2012)., which may indicate the amphipods consumed by M. facilis belong to this suborder. The fish species Cyclothone was documented in one individual. Despite the lack of piscivory in all other individuals examined in this study, the digested state of the prey indicated this was not a net feeding event.

4.5.4. Mentodus mesalirus Mentodus mesalirus is a large-bodied platytroctid that possesses features similar to Maulisia microlepis as well as exhibiting similar dietary habits. Cnidarian tissue was the only prey item observed in 31 of the 47 positive guts, while one individual supplemented its diet through the consumption of a cephalopod. The large gape, minimalistic teeth, and the intestinal structure of this species are well suited for engulfing and digesting large soft- bodied prey (Arai et al., 2003). Mentodus mesalirus had the highest occurrence of parasitism, with helminth eggs or mature worms being found in roughly 2/3 of the dissected individuals. The high occurrence of helminth parasites and a diet consisting primarily of cnidarians may represent an infection pathway (Purcell and Arai, 2001), but a more detailed analysis needs to be conducted.

4.5.5. Platytroctes apus Platytroctes apus has a unique morphology compared to other platytroctids. This species has a relatively compressed, ‘leaf-like’ body, with dorsal and ventral fleshy keels (Appendix B). Platytroctes apus also possesses a small gape, small pectoral fins, potential luminous tissue on the caudal peduncle, and lacks pelvic fins (Matsui and Rosenblatt, 1987). The intestinal structure was simplistic compared to the other examined species, lacking any corkscrew pattern and having few, regressed, pyloric caeca. The unique external and internal anatomy of P. apus may influence the unique dietary habits observed in this species. Consuming primarily crustaceans, the feeding habits of Platytroctes apus differed greatly from the other species examined. Platytroctes apus had the lowest percentage of empty stomachs, contained the most prey items per digestive tract, and had the most diverse diet of the platytroctids in this study. Copepods, principally the genus Pleuromamma, were the most abundant and the most frequently occurring prey. One individual had the remains of 23 copepods, all of which had the same level of advanced digestion indicating simultaneous consumption. Ostracods ranked second in occurrence, found in roughly 2/3 of the positive digestive tracts. Cnidarians and chaetognaths occurred in approximately 1/3 of positive individuals but contributed minimally to the numbers of consumed prey.

5. Summary Platytroctids are major contributors to the bathypelagic fish assemblage of the GoM. This study has documented new occurrences in the GoM for 12 species of platytroctids, with some species representing significant range extensions. In addition to Barbantus curvifrons, Holtbyrnia innesi, Mentodus facilis, and Platytroctes apus, the known platytroctid assemblage of the GoM now includes Holtbyrnia anomala, Holtbyrnia cyanocephala, Holtbyrnia macrops, Maulisia acuticeps, Maulisia argipalla, Maulisia mauli, Maulisia microlepis, Mentodus crassus, Mentodus mesalirus, Mentodus rostratus, Sagamichthys schnakenbecki, and Searsia koefoedi. All platytroctids were caught from nets that went below 700 m, with over 90% of specimens occurring below 800 m depth. The platytroctid assemblage in the GoM was numerically dominated by five species, in order of abundance, Mentodus facilis, Mentodus mesalirus, Maulisia microlepis, Platytroctes apus, and Barbantus curvifrons. The most abundant species were examined for length-wet weight relationships, sex ratios, and dietary habits. The sex ratio did not significantly differ from the expected 1:1 ratio (male:female) for all but one species. The sex ratio of Mentodus facilis significantly favored females, at 1:2.8. Examination of the dietary habits revealed a feeding strategy centered on zooplanktivory. The diet of Platytroctes apus was dominated by crustacean zooplanktivory, primarily consisting of copepods and ostracods. Mentodus mesalirus and Maulisia microlepis fed extensively on gelatinous zooplankton. Mentodus facilis and Barbantus curvifrons shared a similar feeding strategy focused on chaetognaths, copepods, and ostracods, with M. facilis exhibiting a slightly greater reliance on ostracods and gelatinous prey. Nematocysts occurred in all species, suggesting cnidarian prey may be consumed throughout the Platytroctidae family. The results from this study provide the first detailed assessment on the trophic ecology of platytroctids, an important bathypelagic taxon. These results provide much needed information on the bathypelagic community by identifying the importance of the “jelly web” as a viable nutrient pathway that connects the deep and upper oceanic ecosystems.

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Appendix A. Length-Wet Weight (WW) relationships for the five most abundant platytroctid species of the Gulf of Mexico.

A Barbantus curvifrons 14 WW = 2×10-7(SL)3.764 12 10 R² = 0.924 8 6 4 Wet Weight Wet (g) 2 D Mentodus mesalirus 0 120 0 50 100 150 -7 3.415 100 WW = 9×10 (SL) Standard Length (mm) 80 R² = 0.972 60 40 B Maulisia microlepis 20 WW = 1×10-7(SL)3.829 Weight Wet (g) 0 120 R² = 0.884 0 50 100 150 200 250 100 Standard Length (mm) 80 60 40

20 Wet Weight Weight Wet (g) 0 80 130 180 230 Standard Length (mm) E Platytroctes apus WW = 3×10-6(SL)3.264 40 R² = 0.927 30 C Mentodus facilis 20 -6 3.289 14 WW = 2×10 (SL) 10 12 R² = 0.905 Weight Wet (g) 0 10 0 50 100 150 200 8 6 Standard Length (mm) 4

Wet Weight Weight Wet (g) 2 0 0 50 100 150 Standard Length (mm)

Appendix B. Images of various platytroctids from the Gulf of Mexico taken by Danté Fenolio.

Mentodus mesalirus Maulisia spp.

Mentodus facilis Platytroctes apus

Barbantus curvifrons Searsia koefoedi

Appendix C. Worldwide distributions of all identified species mapped using the Ocean Biogeographic Information System.

Barbantus curvifrons (Roule & Angel, 1931)

Barbantus curvifrons is a wide-ranging bathypelagic species that occurs in temperate to tropical waters of the Atlantic Ocean (Carter, 2002), including the Gulf of Mexico (McEachran and Fechhelm, 1998) and tropical to subtropical waters of the Indian and Pacific Oceans (Orrell and Hartel, 2016). Once thought to be absent from the western Atlantic (Matsui and Rosenblatt, 1987), collections by the Woods Hole Oceanographic Institute represented the first records of B. curvifrons from the east coast of the United States (Moore et al., 2003). This species has a small mouth, 47 unbranched pyloric caeca, possesses a small lateral spine projecting from each side of the tip of the lower jaw, but lacks photophores and premaxillary tusks. The largest recorded specimen is 130 mm SL.

Figure 11. Barbantus curvifrons landings reported from OBIS.

Holtbyrnia anomala Krefft 1980

Holtbyrnia anomala occurs from the boreal waters of the Denmark Straits to the tropical Atlantic waters (Matsui and Rosenblatt, 1987). The depth range for this species is reported to be 700–2700 m (Quero et al., 1990). This species has a large head that is more than one-third of the body length, a pointed snout that ends in forward-facing premaxillary tusks, 5–11 pyloric caeca producing 10–21 terminal diverticulae, and rudimentary photophores. The largest recorded specimen is 230 mm SL (Matsui and Rosenblatt, 1987). The three individuals collected during the ONSAP cruise series represent the first records for the GoM.

Figure 12. Holtbyrnia anomala landings reported from OBIS.

Holtbyrnia cyanocephala (Krefft, 1967)

Holtbyrnia cyanocephala is a rarely caught species from the equatorial eastern and western Atlantic and the Indian Ocean. This species seems to have a disjunct distribution between the Atlantic and the Indo-Pacific, with absences from the eastern Pacific. H. cyanocephala possess a shallow, moderately compressed body, photophores, forward-facing tusks, and a large mouth with maxilla extending behind the eyes (Matsui and Rosenblatt, 1987). The recorded depth distribution for Holtbyrnia cyanocephala is 150–1500 m (Quero et al., 1990). The largest recorded specimen is 221 mm (Matsui and Rosenblatt, 1987). The five specimens collected during the ONSAP cruise series represent the first records for the GoM.

Figure 13. Holtbyrnia cyanocephala landings reported from OBIS.

Holtbyrnia innesi (Flower, 1934)

Holtbyrnia innesi is a meso- to bathypelagic species recorded from 100–1500 m in the temperate and tropical Atlantic and eastern Pacific Oceans (Quero et al., 1990). This species has also been reported in the GoM, the Bering Sea, and the central North Pacific (Matsui and Rosenblatt, 1987). Holtbyrnia innesi has an elongate and deep body with photophores, a large mouth with maxilla extending past the eye, and forward-facing tusks off the premaxilla. The largest recorded specimen is 240 mm (Carter, 2002).

Figure 14. Holtbyrnia innesi landings reported from OBIS.

Holtbyrnia macrops Maul, 1957

Holtbyrnia macrops is a meso- to bathypelagic species occurring from 300–1000 m during the day, but has been shown to migrate as shallow as 100 m at night (Quero et al., 1990). Previously known only from the Denmark Straits and Icelandic waters in the eastern Atlantic (Matsui and Rosenblatt, 1987; Quero et al., 1990), this species has recently been documented in the South Atlantic and West Indian Ocean (Porteiro et al., 2017). This species possesses a large head that is about one-third its body length, a pointed snout that ends with forward facing premaxillary tusks, nine pyloric caeca that produce 10–22 terminal diverticulae, and photophores. The largest recorded specimen is 200 mm (Carter, 2002). The four individuals collected during the ONSAP cruises represent the first record from the GoM.

Figure 15. Holtbyrnia macrops landings reported from OBIS.

Maulisia acuticeps Sazonov, 1976

Maulisia acuticeps is a rare meso- to bathypelagic species occurring from 800– 1500 m. This species is known from a single specimen collected off the west coast of South Africa and limited records throughout the Pacific Ocean, including Japan, Australia, and Peru (Orrell and Hartel, 2016; Shinohara et al., 2009). The species possesses an elongate body with a relatively large head, large mouth with the maxilla ending behind the eye, a long snout that terminates in forward-facing tusks, six primary pyloric caeca with 10 terminal diverticula, and no photophores (Matsui and Rosenblatt, 1987). The one specimen collected during the ONSAP cruise series represents the first record for the GoM.

Figure 16. Maulisia acuticeps landings reported from OBIS.

Maulisia argipalla Matsui & Rosenblatt, 1979

Maulisia argipalla is a mesopelagic species occurring from 850–1000 m with a circumglobal distribution, excluding polar waters (Quero et al., 1990). This species possesses a large head that is roughly one-third of the body length, a pointed snout that terminates with forward facing premaxillary tusks, six to eight pyloric caeca, and photophores (Matsui and Rosenblatt, 1987). The 15 individuals collected from the ONSAP cruise series represent the first from the GoM.

Figure 17. Maulisia argipalla landings reported from OBIS.

Maulisia mauli Parr, 1960

Maulisia mauli is a meso- to bathypelagic species with circumglobal distribution that occurs from temperate to tropical Atlantic waters (Carter, 2002) with scattered records noted in the Indian and Pacific Oceans (Porteiro et al., 2017). This species possesses a large head that is more than one-third of its body length, a pointed snout that terminates in forward-facing premaxillary tusks, six to seven pyloric caeca, and photophores (Matsui and Rosenblatt, 1987). The three individuals collected from the ONSAP cruise series represent the first records for the GoM.

Figure 18. Maulisia mauli landings reported from OBIS.

Maulisia microlepis Sazonov & Golovan, 1976

Maulisia microlepis is a bathypelagic to benthopelagic species recorded from 500-2000 m depth (Bianchi et al., 1999). It is known to occur in the cool waters of the temperate Atlantic (Carter, 2002; Orrell and Hartel, 2016) with scattered records in the Indian Ocean and around Australia (Porteiro et al., 2017). This species possesses a large, elongate body, a large head, about one-third in body length, a pointed snout that terminates in forward-facing premaxillary tusks, with approximately 45 pyloric caeca producing 5–15 terminal diverticulae, and no photophores (Matsui and Rosenblatt, 1987). The 52 individuals collected during the ONSAP cruise series represent the first records for the GoM.

Figure 19. Maulisi microlepis landings reported from OBIS.

Mentodus crassus Parr, 1960

Mentodus crassus is a bathypelagic species reported from 800–1500 m depth. Previous records are known from the eastern tropical Pacific and the western South Atlantic Oceans (Matsui and Rosenblatt, 1987; Orrell and Hartel, 2016). This species possesses a moderately deep, elongate body, with a large head and a large mouth with maxilla ending well behind the eyes, and a long snout that terminates in forward-facing premaxillary tusks, and no photophores (Matsui and Rosenblatt, 1987). The five individuals collected during the ONSAP cruise series represent first records for the GoM and the northern Atlantic.

Figure 20. Mentodus crassus landings reported from OBIS.

Mentodus facilis (Parr, 1951)

Mentodus facilis has been reported to be a bathypelagic species inhabiting depths of 650–2000 m in the eastern central Atlantic, the Indian Ocean, the Pacific Ocean (Orrell and Hartel, 2016), and the Gulf of Mexico (McEachran and Fechhelm, 1998). This species possesses a shallow, elongate body, a short snout with forward facing premaxillary tusks, and no photophores (Matsui and Rosenblatt, 1987).

Figure 21. Mentodus facilis landings reported from OBIS.

Mentodus mesalirus (Matsui & Rosenblatt, 1987)

Mentodus mesalirus can be found at bathypelagic depths in the eastern, north, and south Atlantic Ocean (Orrell and Hartel, 2016). This species is likely circumglobal, as records from the western Indian Ocean and the central North Pacific need verification (Matsui and Rosenblatt, 1987). Mentodus mesalirus possesses a deep, elongate body, a large head with a large mouth with the maxilla ending well behind the eyes, forward facing premaxillary tusks, a cleithral symphysis that ends in a blunt spine, and no photophores (Matsui and Rosenblatt, 1987). The 64 individuals collected during the ONSAP cruise series represent the first records from the GoM.

Figure 22. Mentodus mesalirus landings reported from OBIS.

Mentodus rostratus (Günther, 1878)

Mentodus rostratus is a bathypelagic species recorded from the tropical Atlantic, Indian, and northwestern Pacific Oceans at depths of 980–2100 m (Quero et al. 1990). This species possesses a large head that is more than one-third its body length, a large mouth with a pointed snout terminating in forward-facing premaxillary tusks, five to eleven pyloric caeca producing 10–21 terminal diverticulae, and no photophores(Matsui and Rosenblatt, 1987). The individual caught during the ONSAP cruises represents the first record for the GoM.

Figure 23. Mentodus rostraus landings reported from OBIS.

Platytroctes apus Günther, 1878

Platytroctes apus is a bathypelagic species known to occur circumglobally in temperate and tropical waters (Carter, 2002). This species occurs in the equatorial Indian, Pacific, and the Atlantic Oceans, including the Gulf of Mexico (McEachran and Fechhelm, 1998; Pakhorukov, 1999). There are scattered records from the Denmark Straits and Bay of Biscay (Quero et al., 1990). This species possesses a highly compressed body with the dorsal and ventral margins forming a fleshy keel. The snout is blunt, with a small mouth possessing no premaxillary tusks; however, the cleithral symphysis unites in a sharp spine. Individuals possess five small pyloric caeca with five to seven terminal lobes, fleshy dorsal and ventral keels, no photophores, and no pelvic fins (Matsui and Rosenblatt, 1987).

Figure 24. Platytroctes apus landings reported from OBIS.

Sagamichthys schnakenbecki (Krefft 1953)

Sagamichthys schnakenbecki is a mesopelagic species occurring in the boreal to tropical northeastern Atlantic waters (Carter, 2002) with scattered records from the eastern South Atlantic along the western African coast (Porteiro et al., 2017). This species possesses an elongate, slender body, with a small head and short snout, yet has a large mouth with maxilla extending well behind the eyes, no premaxillary tusks, photophores are present, and pyloric caeca number 9–11, with 13–20 terminal lobes (Matsui and Rosenblatt, 1987). The individual collected from the ONSAP cruises represents the first record for the GoM.

Figure 25. Sagamichthys schnakenbecki landings reported from OBIS.

Searsia koefoedi Parr 1937

Searsia koefoedi is a widespread meso- to bathypelagic species known from the eastern Atlantic from Greenland to the equator, the Northwest Atlantic to Bermuda, with scattered records from the Caribbean Sea, and the equatorial Pacific and Indian Oceans (Moore et al., 2003; Porteiro et al., 2017). This species possesses a compressed, elongate body, with a short snout and small mouth with incurved premaxillary tusks, four to six pyloric caeca with 9–19 terminal lobes, and photophores (Matsui and Rosenblatt, 1987). The five individuals collected during the ONSAP cruise series represent the first records from the GoM.

Figure 26. Searsia koefoedi landings reported from OBIS.

Appendix D. Sample data from Pisces trawls that contained new records for platytroctid species

Solar Depth Max Deployed Latitude Longitude Cycle Code Depth (m) (°N) (°W) Species Counts Station Date Quantifiable

Maulisia argipalla 1 B287 N 05-Dec-10 Deep 1198 27.99522 87.48168 Non-quantitative

Maulisia microlepis 1 B251 D 11-Dec-10 Deep 1495 28.2031 87.53883 Quantitative

Holtbyrnia macrops 1 B248 D 15-Dec-10 Deep 1242 27.49007 88.06248 Quantitative

Mentodus crassus 5 SW-8 D 17-Dec-10 Deep 1624 27.0234 88.40997 Quantitative

Maulisia microlepis 1 SW-8 N 17-Dec-10 Deep 1362 27.0343 88.95456 Quantitative

Mentodus mesalirus 1 B249 N 18-Dec-10 Deep 1283 27.48834 88.91715 Quantitative

Maulisia mauli 1 B249 D 19-Dec-10 Deep 1170 27.4833 88.62716 Quantitative

Mentodus mesalirus 1 B251 N 19-Dec-10 Deep 920 28.50222 88.04665 Quantitative

Maulisia microlepis 2 B252 N 22-Mar-11 Deep 28.58411 88.48417 Non-quantitative

Maulisia microlepis 5 B287 N 23-Mar-11 Deep 3800 28.06432 91.09155 Non-quantitative

Holtbyrnia macrops 1 B287 N 24-Mar-11 Shallow 27.87177 89.99792 Non-quantitative

Maulisia microlepis 1 B082 N 24-Mar-11 Deep 3800 27.99738 89.99792 Non-quantitative

Maulisia mauli 1 B082 N 24-Mar-11 Deep 3800 27.99738 90.00746 Non-quantitative

Maulisia microlepis 1 B082 D 25-Mar-11 Deep 3800 28.00543 89.43223 Non-quantitative

Maulisia mauli 1 B249 N 27-Mar-11 Deep 3800 27.64613 89.47699 Non-quantitative

Maulisia acuticeps 1 B064 D 28-Mar-11 Deep 3800 27.57249 89.39846 Non-quantitative

Mentodus mesalirus 1 B064 D 28-Mar-11 Deep 3800 27.57249 87.51079 Non-quantitative

Mentodus mesalirus 1 SW6 D 30-Mar-11 Deep 3800 27.09669 87.53911 Non-quantitative

Mentodus mesalirus 1 B252 D 23-Jun-11 Deep 1355 28.4433 87.96094 Quantitative

Mentodus mesalirus 2 B287 N 23-Jun-11 Deep 1439 28.06463 87.95433 Quantitative

Mentodus mesalirus 1 B287 D 24-Jun-11 Deep 1435 28.08447 88.46374 Quantitative

Maulisia argipalla 1 B287 D 24-Jun-11 Deep 1435 28.08447 88.46374 Quantitative

Mentodus mesalirus 1 B082 N 24-Jun-11 Deep 1418 28.07621 89.02774 Quantitative

Maulisia microlepis 1 B082 D 25-Jun-11 Deep 1412 28.05482 89.05439 Quantitative

Maulisia microlepis 1 B249 D 26-Jun-11 Deep 1271 27.44389 89.05439 Quantitative

Maulisia microlepis 4 B249 N 26-Jun-11 Deep 1350 27.45312 88.91279 Quantitative

Mentodus mesalirus 3 B064 D 27-Jun-11 Deep 1206 27.47659 88.91279 Quantitative

Mentodus mesalirus 3 B064 N 27-Jun-11 Deep 1428 27.51459 88.40785 Quantitative

Maulisia microlepis 1 B064 N 27-Jun-11 Deep 1428 27.51459 88.40785 Quantitative

Maulisia microlepis 3 B083 N 28-Jun-11 Deep 1401 27.92972 88.44988 Quantitative

Maulisia microlepis 4 B083 D 29-Jun-11 Deep 1448 27.9394 88.85478 Quantitative

Maulisia microlepis 1 B251 D 30-Jun-11 Deep 1082 28.55808 88.85478 Non-standard

Maulisia microlepis 1 B251 N 30-Jun-11 Deep 1143 28.53225 87.91488 Quantitative

Maulisia microlepis 3 SW8 N 07-Jul-11 Deep 1319 26.97303 88.4191 Quantitative

Maulisia microlepis 3 SW8 D 08-Jul-11 Deep 1382 26.97845 88.4191 Quantitative

Searsia koefoedi 1 SW8 N 08-Jul-11 Shallow 709 26.98606 88.55831 Quantitative

Maulisia microlepis 6 SW7 D 09-Jul-11 Deep 1395 27.05238 91.00331 Quantitative

Maulisia microlepis 3 SW7 N 09-Jul-11 Deep 1417 26.97166 91.00331 Quantitative

Holtbyrnia cyanocephala 1 SW6 D 10-Jul-11 Shallow 756 26.92704 90.46885 Quantitative

Maulisia argipalla 1 SW5 D 11-Jul-11 Deep 1327 27.08404 90.46885 Quantitative

Searsia koefoedi 1 SW5 N 11-Jul-11 Shallow 719 26.95287 90.52914 Quantitative

Maulisia microlepis 1 SW5 N 11-Jul-11 Deep 1367 27.02341 90.52914 Quantitative

Maulisia microlepis 2 SW5 N 11-Jul-11 Deep 1367 27.02341 90.52914 Quantitative

Maulisia microlepis 1 B248 N 12-Jul-11 Deep 1310 27.54685 90.021 Quantitative

Mentodus mesalirus 1 B252 D 08-Sep-11 Deep 1484 28.51038 90.021 Quantitative

Maulisia argipalla 1 B252 D 08-Sep-11 Deep 1484 28.51038 90.021 Quantitative

Mentodus mesalirus 4 B252 D 08-Sep-11 Deep 1484 28.51038 90.0069 Quantitative

Mentodus mesalirus 2 B252 N 08-Sep-11 Deep 1392 28.54027 89.48528 Quantitative

Mentodus mesalirus 1 B287 D 09-Sep-11 Deep 1495 27.97655 89.48528 Quantitative

Mentodus mesalirus 1 B287 D 09-Sep-11 Shallow 761 27.99671 89.5178 Quantitative

Mentodus mesalirus 2 B287 N 09-Sep-11 Deep 1313 27.95747 89.41349 Quantitative

Mentodus mesalirus 1 B082 D 10-Sep-11 Deep 1383 28.02396 89.40643 Quantitative

Mentodus mesalirus 2 B082 N 10-Sep-11 Deep 1447 28.06027 87.8729 Quantitative

Mentodus mesalirus 2 B249 N 11-Sep-11 Deep 1405 27.54235 87.50623 Quantitative

Searsia koefoedi 1 B249 N 11-Sep-11 Deep 1405 27.54235 87.50623 Quantitative

Holtbyrnia cyanocephala 1 B249 N 12-Sep-11 Shallow 746 27.49048 88.4282 Quantitative

Holtbyrnia macrops 1 B249 N 12-Sep-11 Shallow 746 27.49048 88.4282 Quantitative

Mentodus mesalirus 3 B064 D 12-Sep-11 Deep 1333 27.54016 89.5008 Quantitative

Holtbyrnia anomala 3 B064 N 12-Sep-11 Deep 1291 27.52002 89.5008 Quantitative

Holtbyrnia macrops 1 B064 N 12-Sep-11 Deep 1291 27.52002 89.5008 Quantitative

Maulisia microlepis 1 B064 N 12-Sep-11 Deep 1291 27.52002 89.441 Quantitative

Mentodus mesalirus 6 B251 D 14-Sep-11 Deep 1428 28.40444 91.0047 Quantitative

Mentodus rostratus 1 B251 D 14-Sep-11 Shallow 707 28.4443 91.0047 Quantitative

Searsia koefoedi 1 B083 N 14-Sep-11 Deep 1408 27.98592 88.5214 Quantitative

Mentodus mesalirus 4 B083 N 14-Sep-11 Deep 1408 27.98592 88.5214 Quantitative

Mentodus mesalirus 1 B081 D 15-Sep-11 Deep 1377 28.55039 88.5105 Quantitative

Maulisia argipalla 1 B251 N 15-Sep-11 Deep 1408 28.44966 88.50109 Quantitative

Mentodus mesalirus 4 B251 N 15-Sep-11 Deep 1408 28.44966 88.50109 Quantitative

Maulisia argipalla 2 SW8 D 20-Sep-11 Deep 1398 26.9961 87.44774 Quantitative

Maulisia microlepis 1 SW7 D 21-Sep-11 Deep 1422 27.01008 87.38383 Quantitative

Mentodus mesalirus 3 SW7 D 21-Sep-11 Deep 1422 27.01008 87.38383 Quantitative

Maulisia argipalla 1 SW7 D 21-Sep-11 Deep 1422 27.01008 87.38383 Quantitative

Maulisia microlepis 1 SW7 N 21-Sep-11 Deep 1326 26.99571 87.66848 Quantitative

Searsia koefoedi 1 SW7 N 21-Sep-11 Deep 1326 26.99571 87.88012 Quantitative

Mentodus mesalirus 4 SW7 N 21-Sep-11 Deep 1326 26.99571 88.83038 Quantitative

Maulisia argipalla 1 SW7 N 22-Sep-11 Shallow 742 26.99805 88.83038 Quantitative

Maulisia argipalla 2 SW6 N 22-Sep-11 Deep 1330 27.00769 88.83038 Quantitative

Mentodus mesalirus 1 SW6 N 22-Sep-11 Deep 1330 27.00769 88.48408 Quantitative

Sagamichthys 1 SW6 D 23-Sep-11 Deep 1401 27.028 88.48408 Quantitative schnakenbecki

Maulisia argipalla 1 SW6 D 23-Sep-11 Deep 1401 27.028 88.89589 Quantitative

Mentodus mesalirus 2 SW6 D 23-Sep-11 Deep 1401 27.028 88.89589 Quantitative

Maulisia microlepis 1 SW5 N 23-Sep-11 Deep 1423 26.90718 89.04718 Quantitative

Mentodus mesalirus 1 SW5 N 23-Sep-11 Deep 1423 26.90718 89.40791 Quantitative

Maulisia microlepis 1 SW5 D 24-Sep-11 Deep 1423 26.94918 89.41513 Non-quantitative

Mentodus mesalirus 2 B248 N 24-Sep-11 Deep 1424 27.39253 89.97145 Quantitative

Maulisia argipalla 1 B248 D 25-Sep-11 Deep 1409 27.39923 89.97145 Quantitative

Maulisia microlepis 1 B248 D 25-Sep-11 Deep 1409 27.39923 90.5721 Quantitative

Holtbyrnia cyanocephala 3 B248 N 25-Sep-11 Shallow 720 27.38972 90.5721 Quantitative

Mentodus mesalirus 2 B081 N 26-Sep-11 Deep 1516 28.46015 90.99214 Quantitative

Maulisia argipalla 2 B081 N 27-Sep-11 Shallow 747 28.41269 90.99214 Quantitative