scholarly journals Density-dependent condition of juvenile penaeid shrimps in seagrass-dominated aquatic vegetation beds located at different distance from a tidal inlet

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10496
Author(s):  
Zeferino Blanco-Martínez ◽  
Roberto Pérez-Castañeda ◽  
Jesús Genaro Sánchez-Martínez ◽  
Flaviano Benavides-González ◽  
Jaime Luis Rábago-Castro ◽  
...  
Keyword(s):  
Aquatic Vegetation ◽  
Coastal Lagoons ◽  
Negative Relationship ◽  
Tidal Inlet ◽  
Seagrass Beds ◽  
Seagrass Bed ◽  
Density Dependent ◽  
Nursery Habitats ◽  
Shrimp Density ◽  
Penaeid Shrimps

Seagrasses are critical habitats for the recruitment and growth of juvenile penaeid shrimps within estuaries and coastal lagoons. The location of a seagrass bed within the lagoon can determine the value of a particular bed for shrimp populations. Consequently, differences in the abundance of shrimp can be found in seagrasses depending on their location. As shrimp density increases, density-dependent effects on biological parameters are more likely to occur. However, knowledge about density-dependent processes on shrimp populations in nursery habitats remains limited. The present investigation was undertaken to examine the effects of population density on shrimp condition in two selected seagrass beds, located at different distance from a tidal inlet, one 25 km away (distant) and the other 1 km away (nearby), in a subtropical coastal lagoon. The study was based on monthly samplings during one year in Laguna Madre (Mexico), performing a total of 36 shrimp trawls (100 m2 each one) within each seagrass bed (n = 3 trawls per bed per month for 12 months). Shrimp density was related to the proximity to the tidal inlet (higher density was consistently observed in the nearby seagrass bed), which in turn adversely affected the condition of both species studied (Penaeus aztecus and P. duorarum). In this regard, the present study provides the first evidence of density-dependent effects on shrimp condition inhabiting a nursery habitat. Both shrimp species exhibited a negative relationship between condition and shrimp density. However, this pattern differed depending on the proximity to the tidal inlet, suggesting that shrimp populations inhabiting the nearby seagrass bed are exposed to density-dependent effects on condition; whereas, such effects were not detected in the distant seagrass bed. Shrimp density within the distant seagrass bed was probably below carrying capacity, which is suggested by the better shrimp condition observed in that area of the lagoon. Intra and interspecific competition for food items is surmised to occur, predominantly within seagrass beds near the tidal inlet. However, this hypothesis needs to be tested in future studies.

Does the relative value of submerged aquatic vegetation for penaeid shrimps vary with proximity to a tidal inlet? Preliminary evidence from a subtropical coastal lagoon

2017 ◽  
Vol 68 (3) ◽  
pp. 581 ◽  
Author(s):  
Zeferino Blanco-Martínez ◽  
Roberto Pérez-Castañeda
Keyword(s):  
Submerged Aquatic Vegetation ◽  
Aquatic Vegetation ◽  
Explanatory Variable ◽  
Coastal Lagoons ◽  
Penaeid Shrimp ◽  
Preliminary Evidence ◽  
Tidal Inlet ◽  
Relative Value ◽  
A Site ◽  
Shrimp Abundance

The value of submerged aquatic vegetation (SAV) as a nursery habitat for penaeid shrimp has been recognised previously; however, the importance of SAV in terms of its distance from a tidal inlet (a site through which shrimp postlarvae migrate into coastal lagoons) has not been evaluated. In the present study, the effect of proximity to a tidal inlet on the relative importance of SAV beds for Farfantepenaeus shrimp was evaluated in the Laguna Madre of Tamaulipas (Mexico). Sampling was performed monthly from February to December 2005, diurnally and nocturnally, in two SAV bed areas, one 25km (distant) and the other 1km (nearby) from the inlet. Densities of shrimp (F. aztecus, F. duorarum and F. brasiliensis) were consistently higher in the nearby SAV bed during both the day and night. Water temperature was the most important explanatory variable of shrimp abundance in both SAV beds. The temperature–abundance relationship was negative in all cases, except in the distant SAV bed at night, when shrimp abundance was positively related to dissolved oxygen and salinity. The nearby SAV bed had higher recruit abundance and supported a greater numbers of juveniles and subadults. In contrast, shrimp abundance in the distant SAV bed was apparently limited by recruitment.

scholarly journals Intra and inter annual variation in a seagrass meadow on the Caribbean coast of Costa Rica: 2009-2015

2018 ◽  
Vol 66 (3) ◽  
pp. 1149 ◽  
Author(s):  
Margarita Loría-Naranjo ◽  
Jimena Samper-Villarreal ◽  
Marylaura Sandoval-Siles ◽  
Jorge Cortés
Keyword(s):  
Costa Rica ◽  
Leaf Area ◽  
Turnover Rate ◽  
Seagrass Meadow ◽  
Seagrass Beds ◽  
Seagrass Bed ◽  
Monitoring Methods ◽  
Caribbean Coast ◽  
Area Index ◽  
The Caribbean

Seagrass beds are an important ecosystem on the Caribbean coast of Costa Rica. At Cahuita National Park (CNP) a seagrass bed at Perezoso has been monitored continually since 1999 within the CARICOMP program. Thalassia testudinum is the dominant seagrass species, in some cases mixed with Syringodium filiforme. The results from the 2009 to 2015 monitoring period are presented here, and contrasted with data before 2009. Total (above and below ground tissue) mean biomass of T. testudinum was higher (1 255.4 ± 146.0 gm-2) than biomass before 2009, with an increasing tendency. However, productivity (1.5±0.59 gm-2d-1) and turnover rate (4.3 ± 1.22 %d-1) were lower than previous monitoring periods. In this period, mean leaf area diminished considerably (4.9 ± 2.30 m2), but leaf area index (LAI) increased (1.9 ± 0.80 m2leafm-2) in comparison to prior monitoring. Productivity, density, turnover rate, LAI and biomass showed intra-annual variations; while mean biomass of T. testudinum did not vary significantly among years. No correlations were found between water salinity, temperature and clarity with seagrass measurements. However, most seagrass parameters were strongly correlated with precipitation. These results highlight the effect of external environmental agents acting on the ecosystem. CNP presents a long-term stable seagrass meadow. However, there are indirect signals, such as high biomass and above-ground biomass proportion, along with low productivity and LAI, which point to a nutrient increment in Perezoso’s seagrass bed. To continue protecting this seagrass bed, it is necessary to improve monitoring methods, and seagrass beds should be included in national conservation policies and monitoring programs.

scholarly journals An integrated population model for estimating the relative effects of natural and anthropogenic factors on a threatened population of Pacific trout

2019 ◽  
Author(s):  
Mark D. Scheuerell ◽  
Casey P. Ruff ◽  
Joseph H. Anderson ◽  
Eric M. Beamer
Keyword(s):  
At Risk ◽  
Population Model ◽  
Habitat Restoration ◽  
Negative Relationship ◽  
Anthropogenic Factors ◽  
List Type ◽  
Population Demographics ◽  
Density Dependent ◽  
Integrated Population Model ◽  
The North

SummaryAssessing the degree to which at-risk species are regulated by density dependent versus density independent factors is often complicated by incomplete or biased information. If not addressed in an appropriate manner, errors in the data can affect estimates of population demographics, which may obfuscate the anticipated response of the population to a specific action.We developed a Bayesian integrated population model that accounts explicitly for interannual variability in the number of reproducing adults and their age structure, harvest, and environmental conditions. We apply the model to 41 years of data for a population of threatened steelhead troutOncorhynchus mykissusing freshwater flows, ocean indices, and releases of hatchery-born conspecifics as covariates.We found compelling evidence that the population is under strong density dependence, despite being well below its historical population size. In the freshwater portion of the lifecycle, we found a negative relationship between productivity (offspring per parent) and peak winter flows, and a positive relationship with summer flows. We also found a negative relationship between productivity and releases of hatchery conspecifics. In the marine portion of the lifecycle, we found a positive correlation between productivity and the North Pacific Gyre Oscillation. Furthermore, harvest rates on wild fish have been sufficiently low to ensure very little risk of overfishing.Synthesis and applications.The evidence for density dependent population regulation, combined with the substantial loss of juvenile rearing habitat in this river basin, suggests that habitat restoration could benefit this population of at-risk steelhead. Our results also imply that hatchery programs for steelhead need to be considered carefully with respect to habitat availability and recovery goals for wild steelhead. If releases of hatchery steelhead have indeed limited the production potential of wild steelhead, there are likely significant tradeoffs between providing harvest opportunities via hatchery steelhead production, and achieving wild steelhead recovery goals.

The impact of ticks on Bufo marinus from native habitats

Parasitology ◽  
1996 ◽  
Vol 113 (2) ◽  
pp. 199-206 ◽  
Author(s):  
M. Lampo ◽  
P. Bayliss
Keyword(s):  
Negative Relationship ◽  
Specific Weight ◽  
Bufo Marinus ◽  
Rate Of Change ◽  
Density Dependent ◽  
Significant Negative Relationship ◽  
Induced Changes ◽  
The Impact ◽  
The Relationship ◽  
Native Habitats

SUMMARYWe analysed the patterns of tick distribution on 2274 adult toads from Venezuela and Brazil, to explore whether these ectoparasites have any impact on the survival of Bufo marinus. A maximum-likelihood analysis showed that aggregation levels of ticks decreased significantly with the mean intensity of infection. This decline could be attributed to a density-dependent reduction of ticks within toads, density-dependent tick-induced toad mortality and/or density-dependent tick-induced changes in toad susceptibility. However, the relationship between the rate of change in tick loads and tick burdens from recaptured toads indicated that neither the loss of ticks within toads nor the toad susceptibility to further infection were dependent upon tick burdens. Therefore, we can indirectly infer that density-dependent tick-induced toad mortality is responsible for the observed decline in aggregation levels with tick age and burdens. On the other hand, a significant negative relationship between tick burdens and the size-specific weight of toads suggested that ticks may also have a significant impact on the patterns of weight deposition of adult toads. This evidence suggests that these ectoparasites may play an important role in regulating the densities of B. marinus in native habitats.

scholarly journals Density-dependent changes in effective area occupied for sea-bottom-associated marine fishes

2016 ◽  
Vol 283 (1840) ◽  
pp. 20161853 ◽  
Author(s):  
James T. Thorson ◽  
Anna Rindorf ◽  
Jin Gao ◽  
Dana H. Hanselman ◽  
Henning Winker
Keyword(s):  
Ideal Free Distribution ◽  
Spatial Dynamics ◽  
Negative Relationship ◽  
Strong Relationship ◽  
Effective Area ◽  
Marine Fishes ◽  
Population Declines ◽  
Density Dependent ◽  
Sea Bottom ◽  
Mixed Support

The spatial distribution of marine fishes can change for many reasons, including density-dependent distributional shifts. Previous studies show mixed support for either the proportional-density model (PDM; no relationship between abundance and area occupied, supported by ideal-free distribution theory) or the basin model (BM; positive abundance–area relationship, supported by density-dependent habitat selection theory). The BM implies that fishes move towards preferred habitat as the population declines. We estimate the average relationship using bottom trawl data for 92 fish species from six marine regions, to determine whether the BM or PDM provides a better description for sea-bottom-associated fishes. We fit a spatio-temporal model and estimate changes in effective area occupied and abundance, and combine results to estimate the average abundance–area relationship as well as variability among taxa and regions. The average relationship is weak but significant (0.6% increase in area for a 10% increase in abundance), whereas only a small proportion of species–region combinations show a negative relationship (i.e. shrinking area when abundance increases). Approximately one-third of combinations (34.6%) are predicted to increase in area more than 1% for every 10% increase in abundance. We therefore infer that population density generally changes faster than effective area occupied during abundance changes. Gadiformes have the strongest estimated relationship (average 1.0% area increase for every 10% abundance increase) followed by Pleuronectiformes and Scorpaeniformes, and the Eastern Bering Sea shows a strong relationship between abundance and area occupied relative to other regions. We conclude that the BM explains a small but important portion of spatial dynamics for sea-bottom-associated fishes, and that many individual populations merit cautious management during population declines, because a compressed range may increase the efficiency of harvest.

scholarly journals Dependence of Caribbean reef fishes on mangroves and seagrass beds as nursery habitats: a comparison of fish faunas between bays with and without mangroves/seagrass beds

2001 ◽  
Vol 214 ◽  
pp. 225-235 ◽  
Author(s):  
I Nagelkerken ◽  
S Kleijnen ◽  
T Klop ◽  
RACJ van den Brand ◽  
EC de la Morinière ◽  
...  
Keyword(s):  
Reef Fishes ◽  
Seagrass Beds ◽  
Caribbean Reef ◽  
Nursery Habitats
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