TRAMPLING, PEELING AND NIBBLING MUSSELS: AN EXPERIMENTAL ASSESSMENT OF MECHANICAL AND PREDATORY DAMAGE TO SHELLS OF MYTILUS TROSSULUS (MOLLUSCA: MYTILIDAE)

Shell damage, if properly recognized, can provide information about biotic interactions between molluscs and their predators. However, it can be difficult to distinguish predatory damage from mechanical breakage, thus making interpretation of damaged modern and fossil shells problematic. To establish a clear-cut distinction between antemortem predatory crab damage and ante- and postmortem mechanical damage in Mytilus trossulus shells, a combined field and experimental approach was used. Mussels were exposed to predation by crabs, tumbled-live, tumbled-dead, and trampled. After 100 h of tumbling, live-collected mussel shells were abraded and disarticulated but not otherwise damaged. Eight percent of the dead-collected shells were broken during tumbling. There was a proportional (length, width, and thickness) size reduction in both tumbled-live and tumbled-dead shells after 100 h. Breakage caused by crab predation under laboratory conditions was ;19% of the prey offered. Three types of diagnostic damage were inflicted by crab predation: nibbles, nibbles and chips, and peels. Trampling and tumbling yielded three diagnostic breakage patterns: crescentic chips, angular chips, and slivered chips. Crushed shells and shells with fractured margins were caused by predation and trampling. Only twenty percent of the trampled-shells could be mistaken for preyed-upon shells. Only twenty-seven percent of the preyed-on shells could be mistaken for mechanically damaged shells. Overall, the source of damage could be correctly identified in 74% of the shells. Proper identification of crab predation in dead shells of this commercially important resource may prove valuable in studies of trophic interactions in modern environments. Inferring levels of crab predation, based on damage in fossil specimens, can be reliable if such analyses are calibrated by experimental studies of living representatives or analog

Would Predatory Drillhole Frequency on Chione spp. Increase under the Suggested Climate Change Scenario? Comparing Pleistocene and Modern Rhodolith Beds

The analysis of predatory drillholes allow paleontologists to reconstruct trophic relationships of ancient systems. To evaluate the potential effects of climate and sea level change on predation frequency by gastropods on bivalves, species of the genus Chione from the Gulf of California were selected because they are a commercially exploited resource - at least locally - and abundant in both modern and Pleistocene (sea level high stand of oxygen substage 5e) samples from rhodolith beds. The present study focused to answer a practical question: would predation on Chione spp. increase under the suggested climate - warming - change scenario? A total of 1,626 clams were examined for predatory drillholes, approximately 10.3% of these were drilled. Examination of the drillholes indicated that naticid gastropods were the main predators (~ 98.2%). Both drilling frequency and percent preyed upon were larger in modern than in fossil clams. The higher values observed in modern samples are likely due to differences in temperature between the two times as shell deposition increases with higher temperatures. The higher temperatures in the Pleistocene likely resulted in increased shell thickness, making drilling by predators more difficult

Would Predatory Drillhole Frequency on Chione spp. Increase under the Suggested Climate Change Scenario? Comparing Pleistocene and Modern Rhodolith Beds

The analysis of predatory drillholes allow paleontologists to reconstruct trophic relationships of ancient systems. To evaluate the potential effects of climate and sea level change on predation frequency by gastropods on bivalves, species of the genus Chione from the Gulf of California were selected because they are a commercially exploited resource - at least locally - and abundant in both modern and Pleistocene (sea level high stand of oxygen substage 5e) samples from rhodolith beds. The present study focused to answer a practical question: would predation on Chione spp. increase under the suggested climate - warming - change scenario? A total of 1,626 clams were examined for predatory drillholes, approximately 10.3% of these were drilled. Examination of the drillholes indicated that naticid gastropods were the main predators (~ 98.2%). Both drilling frequency and percent preyed upon were larger in modern than in fossil clams. The higher values observed in modern samples are likely due to differences in temperature between the two times as shell deposition increases with higher temperatures. The higher temperatures in the Pleistocene likely resulted in increased shell thickness, making drilling by predators more difficult

Fish Assemblage Structure Indicates Limited Restoration Progress over a Lustrum of a Severely Degraded Estuary in Southern Tamaulipas, Mexico

Today the biggest incentive to attempt the restoration and protection of estuarine systems is their widely recognized ecological and economic importance. In the reconstruction of an estuary where the original aquatic communities disappeared before the restoration interventions, the fish assemblage is an adequate source of indicators of initial recovery. Following substantial restoration efforts, this study reports on the biannual for a lustrum monitoring and assessment of a severely degraded estuary (Garrapatas) in terms of its fish assemblage using a reference estuary (Barberena) in Tamaulipas, Mexico. Twenty fishes were associated with the restoring and reference estuaries. Species composition (richness, abundance, dominance) clearly showed differences among sites. No piscivorous estuarine or marine fishes were found in Garrapatas pointing at an unbalanced and incomplete trophic chain. On the other hand, the mangrove plant community appears to have fully recovered. Water parameters were more variable in Barberena compared to the restoring sites, especially salinity, DO, and pH, which were also higher. Estuaries are transitional systems with inherent variation of abiotic parameters. It is proposed that this variability of abiotic parameters still missing in the restored sites, and may be key to the full recovery of biotic assemblages and ecosystem function

PREDATION OF EASTERN COTTONTAIL RABBIT (SYLVILAGUS FLORIDANUS) BY GREAT BLUE HERON (ARDEA HERODIAS)

An opportunistic predation by Great Blue Heron (Ardea herodias) on Eastern cottontail rabbit (Sylvilagus floridanus) was observed in south Texas on 31 Oct 2019. The Great Blue Heron had already captured the Eastern cottontail rabbit at the first observation but the maneuvering process, killing, and ingestion were recorded photographically, which make this observation unique even though this might constitute the second report on Great Blue Heron eating Eastern cottontail rabbits

Identifying nitrogen source and seasonal variation in a Black Mangrove (Avicennia germinans) communityof the south Texas coast

Black mangrove (Avicennia germinans) stands in south Texas grow in association with other autotrophic organisms including herbaceous halophytes and cyanobacterial mats. Despite the relevant ecosystem services provided by this coastal plant community, limited information exists on its functioning, in particular as it pertains to nutrient dynamics, namely nitrogen (N). Nitrogen stable isotopes were used to assess potential N sources for plant growth in this community. Plant tissue (leaves), cyanobacteria, and sediment were sampled once every season for one year. Total N in A. germinans (2.6 %) and associated saltwort (Batis maritima) (2.1 %) was higher than in cyanobacteria (0.6 %), and sediment (0.1 %). Isotopic signatures (δ15N) in A. germinans (5.85 ‰) and B. maritima (4.75 ‰) were more similar to sediment (5.21 ‰) than to cyanobacteria (1.98 ‰), suggesting mangroves and saltwort obtain N mostly from the sediment; no evidence of N transfer from cyanobacteria was found

Biodiversity of forage fishes in the Lower Laguna Madre, southernmost Texas

Coastal estuarine ecosystems serve as nursery habitats for many commercially and recreationally important fishes. Biodiversity is a structural indicator and has been used as a metric for conservation and management. In the hypersaline Lower Laguna Madre of Texas, a variety of organisms makes their living in and around the dominant seagrass vegetation. This study provides a general assessment of forage fishes biodiversity collected seasonally with bag seines in two sites: Holly Beach (HB) and South Bay (SB) within the most southern Texas bay system as part of a broader study on fish biology. A total of 15,880 fishes representing 32 species were collected during four quarterly samplings through a year (11,795 from HB and 4,085 from SB). Both sites are interconnected as no fishes similarities difference were found, nonetheless, the sites’ variable characteristics (i.e. basin area, seagrasses coverage, connection to the Gulf of Mexico) resulted in significant greater species richness, relative abundances, and diversity in HB than SB for most of the year, suggesting differences in habitat quality or at the very least variation in the availability of habitat types, which are known to contribute to differences in fish diversity attributes. - Los ecosistemas de estuarios costeros sirven como hábitats de crianza para muchos peces de importancia comercial y recreativa. La biodiversidad es un indicador estructural y se ha utilizado como métrica para la conservación y la gestión. En la hipersalina Laguna Madre Inferior de Texas, una variedad de organismos vive en y alrededor de la vegetación de pastos marinos dominante. Este estudio proporciona una evaluación general de la biodiversidad de peces de forraje recolectados estacionalmente con redes de cerco en dos sitios: Holly Beach (HB) y South Bay (SB) dentro del sistema de bahías al sur de Texas, como parte de un estudio más amplio sobre la biología de peces. Durante cuatro muestreos trimestrales a lo largo de un año, se recolectaron un total de 15.880 peces (11.795 de HB y 4.085 de SB) que representan 32 especies. Ambos sitios están interconectados, ya que no se encontraron diferencias en las similitudes de peces; sin embargo, las características variables de los sitios (es decir, área de la cuenca, cobertura de pastos marinos, conexión con el Golfo de México) dieron como resultado una riqueza de especies, abundancias relativas y diversidad significativamente mayores en HB que en SB durante la mayor parte del año, lo que sugiere diferencias en la calidad del hábitat o, al menos, variación en la disponibilidad de tipos de hábitat, que se sabe que contribuyen a las diferencias en los atributos de diversidad de peces

Oceanographic conditions and diversity of sea stars (Echinodermata: Asteroidea) in the Gulf of California, México

Species richness is one of the best indicators of biodiversity. However, there are few investigations on concordance of diversity patterns and environmental settings for marine regions. The objectives of this study were to correlate species richness of shallow water (\u3c 200 m deep) sea stars with key oceanographic factors in the Gulf of California, México, and to predict species richness of Asteroidea using multiple regressions. In these analyses the Gulf was divided into nine sections of one degree in latitude (from 23 - 31° N), at each section we recorded: continental shelf area (at 100 and 200 m depth), temperature mean and range at three depth levels (0, 60 and 120 m), thermocline depth, surface nutrient concentrations (nitrates, phosphates and silicates), surface photosynthetic pigment concentration, and integrated productivity. Sea star species richness at each latitudinal section was estimated from literature data, new collections and museum records. Species were assigned to one of the following feeding guilds: predators of small mobile invertebrates (I), detritivores (D), predators of colonial organisms (C), generalist carnivores (G), and planktivores (P). There are 47 shallow water asteroid species in the Gulf of California (16 I, 15 D, eight C, six G, one P and one not assigned). Total species richness and guild species richness showed strong latitudinal attenuation patterns and were higher in the southernmost Gulf, an area characterized by a narrow shelf, high temperature, and low nutrient concentrations. Species diversity for each guild was correlated to a set of oceanographic parameters: temperature, nitrate concentration, and integrated productivity were linked to richness in must cases. We detected that nutrients and surface pigments always presented negative relationships with species richness, indicating that productive environments limit asteroid diversity in the study area. Finally, the postulated regression models to estimate species richness from oceanographic data were significant and highly precise. We conclude that species richness of Asteroidea in the Gulf of California is related to oceanographic conditions and can be estimated from regional oceanographic information

Biodiversity of forage fishes in the Lower Laguna Madre, southernmost Texas

Coastal estuarine ecosystems serve as nursery habitats for many commercially and recreationally important fishes. Biodiversity is a structural indicator and has been used as a metric for conservation and management. In the hypersaline Lower Laguna Madre of Texas, a variety of organisms makes their living in and around the dominant seagrass vegetation. This study provides a general assessment of forage fishes biodiversity collected seasonally with bag seines in two sites: Holly Beach (HB) and South Bay (SB) within the most southern Texas bay system as part of a broader study on fish biology. A total of 15,880 fishes representing 32 species were collected during four quarterly samplings through a year (11,795 from HB and 4,085 from SB). Both sites are interconnected as no fishes similarities difference were found, nonetheless, the sites’ variable characteristics (i.e. basin area, seagrasses coverage, connection to the Gulf of Mexico) resulted in significant greater species richness, relative abundances, and diversity in HB than SB for most of the year, suggesting differences in habitat quality or at the very least variation in the availability of habitat types, which are known to contribute to differences in fish diversity attributes