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Technical Summary

STUDY TITLE: Abundance and Distribution of Commercially Important Estuarine Dependent Species 

Populations within the Gulf of Mexico

REPORT TITLE: Abundance and distribution of commercially important estuarine dependent species 

populations within the Gulf of Mexico

OCS STUDY NUMBER: BOEM Award Number M12AC00002

NUMBER OF PAGES: 60

CONTRACT NUMBER(S): BOEM Award Number M12AC00002

SPONSORING OCS REGION: Atlantic

APPLICABLE PLANNING AREA(S): Northern Gulf of Mexico

FISCAL YEAR(S) OF PROJECT FUNDING: FY 2012: $1,178,680

COSTS BY FISCAL YEAR: FY 2012: $243,266; FY 2013: $231,272.66; FY 2014: $233.030.26; FY2015: 

$235,555.54; FY 2016: $235,555.54

CUMULATIVE PROJECT COST: $1,178,680

COMPLETION DATE OF REPORT: June 2018

PROJECT MANAGER(S): Martin T. O’Connell and Ann M. O’Connell

AFFILIATION (OF PROJECT MANAGER): Pontchartrain Institute of Environmental Sciences, University 

of New Orleans

ADDRESS: University of New Orleans, 2000 Lakeshore Drive, Lakefront, LA 70148

PRINCIPAL INVESTIGATOR(S): Martin T. O’Connell and Ann M. O’Connell

KEY WORDS: Gulf of Mexico, estuarine dependent, abundance, distribution, Callinectes sapidus, 

Farfantepenaeus aztecus, Litopenaeus setiferus

BRIEF ABSTRACT: The northern Gulf of Mexico has some of the most productive estuarine-based 

fisheries in the United States. Over the past two decades, however, the ecosystems in this region have 

experienced large-scale natural and anthropogenic disasters. To assess the status of the local aquatic 

organisms and habitats, we analyzed fishery-independent data collected over three decades (1986–1995, 

1996–2005, and 2006–2015) during spring (April–June) and fall (September–November) from 

southeastern Louisiana, Mississippi Sound, and coastal Alabama. We analyzed fishery-independent data 

from trawl and beach seine collections completed over three decades (1986–2015). 

BACKGROUND: As potential impacts threaten important estuarine-based fisheries, there is a need to 

accurately monitor the response of these coastal communities to environmental changes. Measuring how 

estuarine organisms react to disturbances can, however, be problematic for two reasons. First, estuarine 

organisms are typically resilient to events such as hurricanes, having evolved to withstand violent 

changes in these coastal habitats. Second, environmental conditions in estuaries can be extremely 

variable from year to year, making it difficult to relate abiotic changes to observed biotic changes (e.g., 

changes in a community’s species composition). One method to overcome these two sources of 

ecological “noise” in estuaries is to analyze data sets that encompass large temporal and spatial scales. 

When analyzing estuarine data over a large spatial scale, it is necessary to discern if adjacent regions 
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contain similar communities and habitats due to shared organisms, the migratory nature of many 

estuarine organisms, and shared similarities in environmental conditions

OBJECTIVES: Our first goal was to determine if these three states differed in regard to aquatic 

community species composition and environmental conditions (including static habitat conditions). We 

defined the aquatic community as consisting of all finfish species and three ecologically and economically 

important crustacean species: blue crab (Callinectes sapidus), brown shrimp (Farfantepenaeus aztecus), 

and white shrimp (Litopenaeus setiferus). Our second goal was to determine if individual species and 

environmental conditions changed from 1986–1995 to 1996–2005 and later to 2006–2015, with an 

emphasis on detecting which species experienced the most significant changes during this period. 

METHODS: Analysis of similarity (ANOSIM) was used to compare the species composition among the 

three states. Where biotic analyses showed significant differences in species composition, we used a 

combination of the PRIMER BIOENV routine and principle components analyses (PCA) to test for 

differences in environmental conditions, habitat, and geographic location between areas with different 

communities. Also, the LINKTREE routine statistically tested the relative strength of each environmental 

variable in dividing one community from another. We used a modified “indicator value method” approach 

assess temporal changes in coastal aquatic communities by combining data on species abundance and 

frequency of occurrence over different time periods. For the environmental temporal analyses, we used 

analysis of variance (ANOVA) to test for differences among the three decades for each environmental 

variable (temperature, salinity, and dissolved oxygen). 

RESULTS: Species composition differed significantly among the three states in trawl collections for both 

spring (ANOSIM, R=0.543, p<0.001) and fall (ANOSIM, R=0.722, p<0.001) while beach seine collections 

were not significantly different across the states for either the spring (ANOSIM, R<-0.06, p=0.61) or fall 

(ANOSIM, R<0.167, p=0.14). The greatest habitat factor contributing to these differences was the 

presence of more shell substrate at the Louisiana sites (LINKTREE analysis, B%=86, p<0.05). While 32

species exhibited significant (IndVal, p<0.05) declines in at least one state-season-gear scenario over the 

three decades, blue crab (Callinectes sapidus) and least puffer (Sphoeroides parvus) experienced the 

most declines overall. Four species of flatfishes also experienced multiple declines over the same

periods. Louisiana trawl sites became significantly more saline in both seasons over time; both 

Mississippi spring trawl sites and Alabama trawl sites seasonally became significantly warmer (ANOVA, 

p<0.02 for all comparisons). 

CONCLUSIONS: The observed declines in relative abundance of important species in parallel with largescale environmental changes emphasize the need for continued monitoring and expanded assessment of 

the cumulative effects of potential climatic variability and harvest impacts on the sustainability of 

estuarine-based fisheries and associated populations. 

STUDY PRODUCT(S):

1. O’Connell M, O’Connell A, et al. 2018. Abundance and distribution of commercially important 

estuarine dependent species populations within the Gulf of Mexico. New Orleans (LA): US 

Department of the Interior, Bureau of Ocean Energy Management. 67 p. OCS Study BOEM 2019-

037. Agreement Number M12AC00002. 

2. Copies of the dataset are archived in the NODC
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Figure 1. Trawl (circles) and beach seine (triangles) sites for samples collected from Louisiana, Mississippi, and Alabama in spring (April, May, 

and June) and fall (September, October, November). Recent samples were collected from 2012 to 2016; historical samples were collected at the 

same or nearby sites from 1986 to 2012. Due to limited available shallow-water habitat, samples were collected from only three beach seine sites 

in Mississippi.