Designing cost‐effective artificial reefs: fine‐scale movement and habitat use of Red Snapper ( Lutjanus campechanus ) around a nearshore artificial reef complex

Author(s):  
Kesley Gibson Banks ◽  
Judson M. Curtis ◽  
Jason A. Williams ◽  
Jennifer J. Wetz ◽  
Gregory W. Stunz

<em>Abstract</em>.—Reef-fish assemblage structure was compared among multiple artificial and geologic (i.e., naturally occurring hard bottom) habitats in the northeastern Gulf of Mexico during 2014–2016 as part of a larger fishery-independent survey. Baited remote underwater video systems equipped with stereo cameras were deployed (<em>n </em>= 348) on 11 habitat types, classified through interpretation of side-scan sonar imagery. In the video samples, 11,801 fish were enumerated. Nonparametric analysis of reef-fish assemblages detected four clusters related to habitat; assemblages associated with geologic habitats were distinct, whereas the remaining three clusters represented groupings of artificial habitats of different size, scale, and complexity. While many species, including Vermilion Snapper <em>Rhomboplites aurorubens </em>and Red Snapper <em>Lutjanus campechanus</em>, were observed in greater numbers on artificial reef habitats, most species were observed in all habitats sampled. Among artificial reef habitats, the habitat cluster consisting of unidentified depressions, unidentified artificial reefs, construction materials, and reef modules was similar to geologic habitats in supporting larger individuals, specifically Gray Triggerfish <em>Balistes capriscus </em>and Red Snapper. In contrast, the habitat cluster consisting of smaller, generally solitary chicken-transport cages was inhabited by smaller individuals, including smaller Red Snapper. Although geologic reefs are the predominant reef habitat throughout much of the eastern Gulf, artificial reefs are important locally, especially in the Florida Panhandle. Accordingly, continued incorporation of artificial reef habitats within large-scale fishery-independent monitoring efforts is critical to the accurate assessment of the status of reef-fish stocks on broad spatial scales.


<em>Abstract.</em>—Red snapper, <em>Lutjanus campechanus</em>, (<em>n </em>= 4,317) were captured and tagged at 14 experimental artificial reefs of two designs during quarterly research cruises (<em>n </em>= 17) off coastal Alabama between January 1999 and October 2002. Six-hundred and twenty nine recaptures were reported, representing 578 tagged red snapper. Sixty-five percent of recaptures (<em>n </em>= 412) were made at the site of release on subsequent research cruises, while 217 recaptures were reported by fishers. Eighty-six percent of individuals with known recapture locations moved 2 km or less from the site of release; mean and maximum distances moved were 2.1 km and 201 km, respectively. Nine red snapper moved greater than 80 km. Mean dispersion rate from release sites was 8.6 m d<sup>⁻1</sup>. Annual site fidelity of tagged fish was estimated using nonlinear decay models. Estimated annual site fidelity ranged from 48% to 52% year<sup>⁻1</sup> and was not significantly affected by artificial reef design, reef fish biomass at the site of release, or artificial reef densities surrounding each tagging site. Growth rates were estimated by regressing the change in red snapper total length versus the days a fish was at liberty. Mean growth rate for all recaptured fish was 0.206 mm d<sup>⁻1</sup>. Growth rates were significantly affected by reef size (faster at larger experimental reefs) and reef fish biomass (slower at tagging sites supporting low reef fish biomass), but were not affected by artificial reef density. Moderate site fidelity and low dispersion rates during our study provide support for the hypothesis that artificial reefs off Alabama are suitable habitat for adult red snapper. However, characteristics of artificial reefs, such as reef size and standing stock biomass, may affect red snapper growth. Furthermore, ratios of instantaneous growth in weight to total mortality (<EM>G/Z</EM>) suggest artificial reefs off Alabama serve as net sinks (i.e., <EM>G/Z </EM>< 1) of red snapper biomass under current fishing mortality rates.


<em>Abstract</em>.—Visual census scuba surveys (<em>n </em>= 87) were used to compare fish assemblages among three artificial reef types: big reefs (e.g., ships), tank reefs (i.e., U.S. Army tanks) and small reefs (e.g., metal cages and concrete pyramids), over three locations on the continental shelf (inner shelf, 18–26-m depths; mid-shelf, 26–34-m depths; outer shelf, 34–41-m depths) from April 20, 2012 to November 30, 2015 in the northeast Gulf of Mexico. These surveys identified 66 fish taxa (lowest taxon: 58 species, five genera, three families), and 65 taxa were used in community comparisons. Artificial reefs were dominated by Red Snapper <em>Lutjanus campechanus </em>(35.3% of total fish observed), Tomtate <em>Haemulon aurolineatum </em>(22.4%), Vermilion Snapper <em>Rhomboplites aurorubens </em>(19.5%), Atlantic Spadefish <em>Chaetodipterus faber </em>(7.0%), Greater Amberjack <em>Seriola dumerili </em>(3.0%), and Gray Triggerfish <em>Balistes capriscus </em>(1.8%). These six most abundant species comprised 89% of the total number of individuals observed. Red Snapper and Greater Amberjack mean sizes (total length mm) were larger at big reefs, Vermilion Snapper and Atlantic Spadefish were larger at tank reefs, and Tomtates were larger at small reefs. Red Snapper, Atlantic Spadefish, and Greater Amberjacks were larger at reefs on the outer shelf, and Red Snapper, Tomtates, Vermilion Snapper, Atlantic Spadefish and Greater Amberjacks were larger in the spring. Richness and Shannon–Wiener diversity indices were higher on big reefs and tank reefs compared to small reefs. Evenness, richness, and Shannon–Wiener diversity were lower in winter compared to other seasons. Fish assemblages, based on Bray–Curtis similarities, were different among reef type, location, and season, but no interactions effects were identified. In the present study, fish assemblages on big reefs were more similar to assemblages on tank reefs in comparison to small reefs. The larger size, longer life span, and relative stability of the big reefs and tank reefs were the reef attributes most likely responsible for these assemblage associations. Similarly, more stable conditions at deeper depths (less affected by tropical storms) and proximity to deepwater reef fish communities (e.g., pinnacle reefs) most likely influenced the increased assemblage diversity on the artificial reefs at outer-shelf locations. Diversities and densities were highest during the fall. This was most likely due to increased recruitment of tropical species and new age-0 recruits that were spawned during the same year. The attributes of all artificial reefs are not identical; consequently, it is important for managers to consider how reef type, shelf location, and season affect each species’ affinity and association with artificial reefs.


<em>Abstract</em>.—Identifying morphometrics, age composition, and growth of Red Snapper <em>Lutjanus campechanus </em>(Poey, 1860) in the Gulf of Mexico is crucial for management of this valuable species. Red Snapper are highly associated with artificial reefs situated off the coast of Texas. Artificial reefs, two in federal waters (offshore) and two in state waters (inshore), were sampled quarterly from December 2014 through December 2016. Characteristic differences in age and growth patterns at inshore and offshore sites and across sampled sites were compared. Mean ± standard deviation was calculated for total length (TL), weight, and biological age. Red Snapper collected averaged 464.5 ± 92.6 mm in TL, 1.62 ± 1.03 kg, and 3.8 ± 1.5 years. Significant differences in TL, weight, and age were observed across sites but not between inshore and offshore locations. In comparing 12 previous Red Snapper length-at-age (0–25 years) studies across the Gulf of Mexico, results were similar except for two studies significantly different from one another, but none with respect to our study. Our findings suggest that Red Snapper populations are young and restricted to one or two spawning years before capture on artificial reefs. Continued management of fisheries associated with these reefs are necessary to increase the stock and eventually lead to robust and sustainable fisheries.


2019 ◽  
Vol 209 ◽  
pp. 49-57 ◽  
Author(s):  
Catheline Y.M. Froehlich ◽  
Andres Garcia ◽  
Richard J. Kline

2009 ◽  
Vol 08 (02) ◽  
pp. 175-188 ◽  
Author(s):  
J. Brooke Shipley ◽  
Margaret F. Shipley

A rough set theory model utilising fuzzy sets was developed to investigate artificial reef placement based on fish ecosystem components. The model incorporates consumption estimates and presumed foraging behavior to provide a rule-based approach to determine how far apart artificial reefs must be placed to eliminate density-dependent competition for prey resources. Simulation of the ecosystem parameters and potential reef distances as triangularly defined fuzzy sets generates input into the rules. Then, based upon the strength of belief in a rule, the artificial reef placement location can be accepted or rejected as being conducive to consumption at the reef and foraging behaviour of the species. Ease of utilisation of the model is highlighted by spreadsheet application to a red snapper (Lutjanus campechanus) ecosystem in Gulf of Mexico waters off the coastal shelf of Alabama. Implications exist for similar applications to other ecosystems and different fish species. Further applications are relevant beyond fish management when viewed as a general managerial decision-making process involving fuzzy sets and simulation.


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