Literatura académica sobre el tema "Otolith chemistry"

<em>Abstract</em>.—Natural chemical markers in otoliths and fin rays have proven useful for retrospectively describing environmental history of fishes in a variety of environments. However, no studies have applied this technique to catfishes or evaluated catfish pectoral spine chemistry as a nonlethal alternative to otolith chemistry. We characterized relationships between water, otolith, and pectoral spine (articulating process) chemistry for channel catfish <em>Ictalurus punctatus</em>, flathead catfish <em>Pylodictis olivaris</em>, and blue catfish <em>I. furcatus</em> and determined the accuracy with which fish could be classified to their environment of capture using otolith and pectoral spine chemical signatures. Fish and water samples were collected from nine sites during 2009. Otolith, spine, and water samples were analyzed for Sr:Ca and Ba:Ca; otolith δ<sup>18</sup>O and δ<sup>13</sup>C and water δ<sup>18</sup>O were also measured. Water, otolith, and spine Sr:Ca were highly correlated, as were water and otolith δ<sup>18</sup>O. Relationships between water, otolith, and spine chemistry did not differ among species. Otolith Sr:Ca, δ<sup>18</sup>O, and δ<sup>13</sup>C and spine Sr:Ca differed among sites, reflecting geographic differences in water chemistry. Neither otolith nor spine Ba:Ca differed among sites despite intersite differences in water Ba:Ca. Both otolith Sr:Ca, δ<sup>18</sup>O, and δ<sup>13</sup>C and fin spine Sr:Ca classified fish to their environment of capture with a high degree of accuracy, except in the middle and lower Mississippi River where many recent immigrants appeared to be present. Natural chemical signatures in otoliths or pectoral spines will likely be effective for reconstructing environmental history of catfishes when spatial differences in water chemistry are present, enabling investigations of stock mixing and recruitment sources for these species.

<i>Abstract</i>.—The population structure of the eastern Australian salmon <i>Arripis trutta </i>stock in the waters of southeastern (SE) Australia was examined using information provided by historical as well as current data sources. An extensive tag-recapture program and aging study undertaken during the 1960s demonstrated widespread mixing of the <i>A. trutta </i>population in SE Australian waters and established a robust model of general movement of fish from Tasmania north to Victoria and NSW with the approach of sexual maturity at ~four years of age. However, this work also hypothesized that the portion of the stock at Flinders Island in Tasmanian waters was resident and did not undergo this northward migration. Otolith chemistry analyses were therefore used as a tool in a ‘weight of evidence’ approach to further examine the population structure of the <i>A. trutta </i>stock in SE Australia. Samples of five year old <i>A. trutta </i>for analysis of otolith chemistry were collected over seven weeks from two sites (10 per site) within each of four locations: northern NSW, southern NSW, Victoria and Tasmania. The cores and edges of otoliths were analyzed using laser ablation inductively coupled plasma mass spectrometry. Univariate analyses did not find spatial differences for any of the elements Li, Na, Mg, Mn, Ba or Sr between locations. Multivariate analyses however, did find differences between the multi-element ‘fingerprints’ of fish from Tasmania compared to each of the other locations (which were similar). This difference was driven by a group of fish collected from Flinders Island in north-eastern Tasmanian waters. The fish collected at this site were also significantly smaller at five years of age than fish from all other sites, indicating reduced growth rates. The lack of consequential and definitive differences in otolith chemistry data combined with the highly migratory nature of <i>A. trutta </i>in this region demonstrated by tagging studies confirm that the most likely stock structure model for <i>A. trutta </i>in SE Australia is of a single well mixed biological stock spanning Tasmania, Victoria and NSW with fish moving north from Tasmania to mainland Australia with the approach of sexual maturity. However, the reduced growth rates and distinct elemental signature for <i>A. trutta </i>from Flinders Island highlights the need for further work to examine the preexisting hypothesis of a potential resident sub-population there.

<em>Abstract.</em>—A review of studies examining stage-specific distribution and movement of various life stages of red snapper, <em>Lutjanus campechanus</em>, in U.S. waters of the Gulf of Mexico (GOM) was conducted to draw inference about population structure. Hydrodynamic modeling of neither egg nor larval transport has been conducted for GOM red snapper; thus, the potential for planktonic dispersal among regions is currently unknown. However, recent studies of other reef fishes have demonstrated that larval fishes may not act as passive particles. Postsettlement movement, or the lack thereof, may be just as important for describing population connectivity and structure as planktonic transport. Red snapper juveniles display thigmotaxis and have been shown to undergo an ontogentic shift in which the dimension and complexity of their habitat increases with fish size. Tagging data demonstrate that while a substantial percentage of tagged fish were recaptured near their release sites, movement on the scale of hundreds of km also has been reported. Direct estimates of movement and population mixing from ultrasonic tagging, conventional tagging, and otolith chemistry studies indicate movement of some individuals may be sufficient to promote genetic exchange among regions, but overall movement is likely insufficient to affect population demographic differences observed among regions. Therefore, GOM red snapper meet criteria for consideration as a metapopulation: subpopulations are distinct, dispersal mechanisms exist among subpopulations, and asynchrony in population demographics is apparent among subpopulations.