Five Years Later: An Update on the Status of Collections of Endemic Gulf of Mexico Fishes Put at Risk by the 2010 Oil Spill

Abstract Background The 2010 Gulf of Mexico Oil Spill took place over 180,000 square kilometers during a 12-week period over five years ago; however, this event continues to influence the development and distribution of organisms in and around the region of the disaster. Here we examine fish species that may have been most affected by noting their past distribution in the region of the spill and examining data of known collecting events over the last 10 years (five years prior to the spill, five years post spill). New information We found that more than half of the endemic fish species of the Gulf (45 of 77)


Introduction
The 2010 Gulf of Mexico Oil Spill (also called the Deepwater Horizon/BP disaster/oil spill, or Macondo blowout among others) was the largest accidental spill of oil in history (Crone andTolstoy 2010, Rabalais 2014). Coupled with the fact that it occurred in the deep sea (>1000 m depth) and with the coordinated release of more than a million gallons of dispersant, it is one of the greatest pollution events in history (Goodbody-Gringley et al. 2013). The long lasting effects of the spill are still not fully understood even five years after the event. There is considerable evidence that some species continue to be physically and developmentally challenged by the impact of the spill, particularly fishes Dubansky et al. 2013;Brette et al. 2014;Alloy et al. 2016). However, population studies of fishes remain poorly examined (Fodrie et al. 2014). Although, fisheries for commercial species are better studied, the ichthyofauna as a whole has received little attention. Chakrabarty et al. (2012) listed fish species in need of conservation concern based on their known distribution in relation to the historical surface position of the oil spill. Here we reexamine the distribution of all 77 known endemic Gulf fish species five years after the spill based on collection records (as a reminder endemic means in this context, species only found in the Gulf of Mexico). We compare these post-spill records with those from five years prior to the spill.
These collection records are obtained from natural history museum records of specimen collections. Museum collections are a vital source for biological records (Drew 2011; Rocha et al. 2014). They maintain a record of the world's biodiversity by keeping specimens recorded from a certain area and time allowing comparisons to be made across time and space. With these collections one can compare a changing fauna before and after a catastrophic event, such as an oil spill. The correct identification of specimens is also vital (Chakrabarty et al. 2013), as museum collections are maintained by taxonomists and the specimens and comparative material are at hand, the identifications from these collections are more trustworthy than those from ship records or other sources where specimens are discarded. Here we use these collection records to examine the affects of the 2010 Gulf of Mexico Oil Spill on the endemic fishes of the region.

Methods and Results
The occurrence records of the 77 endemic species of the Gulf of Mexico were tallied using The Global Biodiversity Information Facility and FishNet2 from October-December of 2015. Duplicate events from the two databases were deleted (duplicates were discovered if they had the same museum catalog numbers). A scatter plot graph was then created in Microsoft Excel showing collections five years prior to the 2010 Oil Spill and five years post spill. Only collections records from the Gulf of Mexico were counted (assuming for these endemics that records from outside the region are likely misidentifications).
Scatter plots of endemic fishes from the Gulf of Mexico are shown below with the "Number of Occurrence(s)" on the y-axis vs. the "Number of Years" on the x-axis. Species are listed in alphabetical order. Endemic species that have few or no collections records do not have a scatterplot but details about their last collecting events are presented. The scientific name is also presented followed by common name (when there is one) and family. Spill zone overlap information is from Chakrabarty et al. (2012). If the scientific name has changed in the past five years we show both the old and new names. Conservation information about "Resilience" is taken from FishBase (Froese and Pauly 2016). Resilience is based upon the time it takes to double the species population and are as follows: Very Low (minimum of 14 years to double population); Low (4.5-14 years to double population); Medium (1.4-4.4 years to double population); High (less than 15 months to double population). 1) Alosa alabamae -Alabama Shad -Clupeidae (1% range overlap with spill zone).

Discussion
The continued influence of an oil spill that occurred more than five years ago on the Gulf of Mexico is evident Alloy et al. 2016;Schaefer et al. 2015); however, data about population status, or even tangible proof of the continued existence of many of the Gulf's endemic fish species, is lacking. More than half (45) of the 77 endemic species from the Gulf of Mexico have not been officially collected since the 2010 spill. Of these, nine species have not been collected since before 1980, eight species have not been collected since the 1980s, and two not since the 1990s. Although there is a focus on fisheries data for commercially important species post-spill, the endemic species examined here are among the Gulf species we know the least about. Even with the data presented here our study of collections records must be viewed as a small glimpse into the true effects of the spill. Collections records are not a true estimate of population dynamics; however, in the case of rare and poorly studied species (as is the case with these endemics) -it is our best estimate.
Other species appear to be more common post-spill, with most of the collections occuring in the last five years ( (Schaefer et al. 2015). Although not directly targeted for fisheries these species may have increased in number because they were not collected as by-catch when fishing was closed. Also the increased interest in collecting and studying Gulf species post spill may have increased efforts to identify and catalogue these species. We also note here that the collections efforts pre-and post-spill were likely not equal. We therefore cannot do a statistical sampling comparison based on collecting effort.
There are some notable trends among and within groups as well. Of the six eels in the study (Elopomorpha Families: Ophichthidae, Muraenidae, Congridae) only one species, Ophichthus rex had a high percentage of its range in the region of the spill (82%) and it has been collected once since the spill. However, eel species in general are very rare in collections, and little or no data about any of the endemic eels from the Gulf of Mexico is known (9 total collection records, all post spill).
Of the seven cartilaginous fishes (Elasmobranchii Families: Anacanthobatidae, Rajidae, Etmopteridae, Triakidae) most had a high proportion of their range in the area of the spill zone but most have post-spill collections. The exception being the rare Anacanthobatis folirostris, which has no collection records since 2004. These elasmobranchs all have low resiliency, with populations doubling time between 4.5-14 years (Froese and Pauly 2016). Most members of the small but diverse members of gobies (Gobioidei) and blennies (Blennioidei) lack sufficient information (in being collected mostly before 2005), as is the case for most of the ten coral associated endemic Gulf species (Table 1). Inshore brackish fishes such as those in the families Lepisosteidae, Clupeidae, Atherinopsidae, Fundulidae, Poeciliidae, and Cyprinodontidae, were mainly out of the area of the immediate spill (i.e., little overlap with the region of the spill as initially measured) and are among the most collected species among Gulf endemics (Table 1 ). However, although the collections may be high, the documented developmental impairment of near shore species points to the fact that even these species are not out of harms way (Dubansky et al. 2013). Additionally, the influence of the oil slick at the surface on pelagic larvae and in the deep-sea on individuals that are rarely seen will never be completely known (Fodrie and Heck 2011).  Chakrabarty et al. 2012). Taxa that were deemed ''Species of Greatest Concern'' by Chakrabarty et al. (2012) are in bold. These species had 35% of their historical occurrence records in the region of the oil spill. More than quarter of the Gulf of Mexico endemic fish species (20) had greater than 35% of their historical records in the area of the spill zone (Chakrabarty et al. 2012; those in bold text in Table 1). These species were identified by Chakrabarty et al. (2012) as being in the highest potential impact category. Of these species half (10 species) still lack any collection records post spill. We note that both GBIF and FishNET are not perfect records of all collecting events or even all museum collections. Also we note that these databases are dynamic and change on a near daily basis as museum records are uploaded and updated. For that reason the data in this paper should be taken as a snapshot of the information available at this time. It is clear more work needs to be done to find and potentially protect these endemic taxa. Future work will include citizen science projects by the authors (see Acknowledgements) and others, that will target Gulf endemics and add data, museum records, and increase community awareness. We hope this study helps focus conservation efforts on those species that lack the most information, or that have not been collected post-spill.