Advances in Marine Biology最新文献

The invasive brittle star Ophiothela mirabilis (family Ophiotrichidae), a tropical Indo-Pacific endemic species, first reported in Atlantic waters off southern Brazil in 2000, has extended its range northward to the Caribbean Sea, to the Lesser Antilles in 2011, and was first reported in south Florida in January 2019. Its occurrence in southeast Florida extends along nearly 70km of coastline, from near the Port of Miami, Miami-Dade County, northward to Deerfield Beach, Broward County. It occurs abundantly as an epizoite on octocorals, attaining population densities of 25 individuals and more per 10-cm long octocoral stem. The surface texture of octocoral hosts (rough, smooth) did not affect the densities of the ophiuroid epizoites, and there were significantly greater abundances on octocorals during two winter sampling periods than in the summer. Beige and orange-coloured morphs are sometimes present on the same octocoral stem. Gut content analysis supported a suspension feeding mode, revealing essentially identical ingested items in both colour morphs with a preponderance of amorphous detritus and filamentous algae. Molecular genetic evidence (COI & 16s) has established the identity of O. mirabilis and its relationship to invasive Brazilian populations. The orange and beige morphs form two distinct, but closely related lineages that may represent two separate introductions. The orange morph shares haplotypes with Brazilian and Caribbean specimens suggesting a further range expansion of the 'original' invasion. The beige morph, however, shares haplotypes with specimens from the Mexican Pacific and Peru and potentially represents a secondary introduction. Traits promoting dispersal and establishment of this species in new habitats are manifold: vagility and ability to cling tightly to diverse host taxa (e.g. sponges, cnidarians, bryozoans, and echinoderms), frequent asexual reproduction (fissiparity), suspension feeding, including a wide range of dietary items, possession of integument-covered ossicles and arm spines offering protection from predators, and an effective competitive edge over associated microbiota for substrate space.

The two banana prawns Penaeus merguiensis and P. indicus are arguably the most commercially important species of penaeid prawns in the tropical and sub-tropical Indo-West Pacific region. They are fecund, short-lived, and have a complex life history involving offshore spawning, inshore mangrove-lined nursery grounds, and migrations between the two locations. We have reviewed and assessed published research on: the fisheries and aquaculture; taxonomy and identification; distribution and habitat preferences; growth; mortality; food and feeding; predation, and the importance of the mangrove habitat to banana prawns. We have examined the life history patterns of these two banana prawns and the many environmental and biological factors that affect different life history stages, often resulting in large interannual variations in abundances of adult prawns and commercial catches. We have also reviewed research on the ecosystem relationships involving these prawns, including fishery impacts on the environment and other species caught as bycatch. In reviewing the published information on factors affecting recruitment dynamics and variability, we have sometimes found contrasting and confounding results, suggesting that these factors are not yet fully understood. Therefore, for each aspect of the prawns' biology we have pointed to areas with incomplete or conflicted understanding, which will hopefully guide future research on these extremely valuable prawn species.

Octocorals are important zoobenthic organisms, contributing to structural heterogeneity and species diversity on hardgrounds. Their persistence amidst global coral reef degradation and ocean acidification, has prompted renewed interest in this taxon. Octocoral assemblages at 52 sites in continental Ecuador and Galápagos (23 species, 3742 colonies) were examined for composition, size distributions within and among populations, and connectivity patterns based on ocean current models. Species richness varied from 1 to 14 species per site, with the richest sites on the continent. Three assemblage clusters were recognised based on species richness and population size, one with a mix of sites from the mainland and Galápagos (defined by Muricea fruticosa and Leptogorgia alba, Muricea plantaginea and Pacifigorgia darwinii), the second from Santa Elena in southern Ecuador (defined by M. plantaginea and L. alba) and the third from the northernmost sites on the continent, in Esmeraldas (defined by Muricea fruticosa, Heterogorgia hickmani, Leptogorgia manabiensis). Based on biophysical larval flow models with 30, 60, 90-day Pelagic Larval Duration, good connectivity existed along the South American mainland, and from the continent to Galápagos. Connectivity between Galápagos, Cocos, Malpelo and the Colombian mainland may explain the wide distribution of L. alba. Muricea plantaginea had the densest populations with the largest colonies and therewith was an important habitat provider both in continental Ecuador and Galápagos. Continental Ecuador harbours the most speciose populations of octocorals so far recorded in the southern Eastern Tropical Pacific (ETP). Most species were uncommon and possibly vulnerable to local extirpation. The present study may serve as a base line to determine local and regional impacts of future disturbances on ETP octocorals.

Outbreaks of the Pacific crown-of-thorns starfish (COTS; Acanthaster cf. solaris) have been responsible for 40% of the decline in coral cover on the GBR over the last 35 years. With the intensity and frequency of bleaching and cyclonic disturbances increasing, effectively managing these outbreaks may allow reefs an opportunity to recover from these cumulative impacts. Significant research effort has been directed toward developing regional scale models for COTS outbreaks, but these have yet to be fit explicitly to long term time series at the scale of the entire GBR, nor do previous research efforts incorporate explicit estimates of cumulative disturbance history. We developed a stage-based metapopulation model for COTS at a 1×1km resolution using long-term time series and modelled estimates of COTS larval connectivity, nutrient concentrations and important vital rates estimated from the literature. We coupled this metapopulation model to an existing spatially explicit model of coral cover growth, disturbance and recovery across the GBR from 1996 to 2017 to create a metacommunity model. Our results were validated against a spatially and temporally extensive dataset of COTS and coral cover across the GBR, predicting an average coral decline of 1.3% p.a. across the GBR, and accurately recreating coral cover trajectories (mean prediction error=7.1%) and COTS outbreak classification (accuracy=80%). Sensitivity analyses revealed that overall model accuracy was most sensitive to larval predation (boosted regression tree; relative importance=46.7%) and two parameters defining juvenile density dependent mortality (21.5% and 17.5%). The COTS model underestimated peak COTS densities particularly in the Swains and Townsville sectors of the reef, while overestimating COTS density during non-outbreak years. A better understanding of inter-annual variability in larval connectivity, and regionally variable density dependence for adult COTS life stages may improve model fit during these extreme outbreak events. Our model provides a platform to develop upon, and with improvements to estimates of larval connectivity and larval predation could be used to simulate the effects of implementing varying combinations of COTS interventions. This research highlights the importance of the early life history stages of COTS as drivers of outbreak dynamics, emphasizing the need for further empirical research to estimate these parameters.

Chronic coral reef degradation has been characterized by a significant decline in the population abundance and live tissue cover of scleractinian corals across the wider Caribbean. Acropora cervicornis is among the species whose populations have suffered an unprecedented collapse throughout the region. This species, which once dominated the shallow-water reef communities, is susceptible to a wide range of stressors, resulting in a general lack of recovery following disturbances. A. cervicornis is a critical contributor to the structure, function, and resilience of Caribbean coral reefs. Therefore, it is essential to identify the factors that influence their demographic and population performance. Diseases are one of the factors that are compromising the recovery of coral populations. In this chapter, we use size-based population matrix models to evaluate the population-level effect of a Shut Down Reaction Disease (SDR) outbreak, one of the less-understood diseases affecting this coral. The model was parameterized by following the fate of 105 colonies for 2 years at Tamarindo reef in Culebra, Puerto Rico. SDR, which affected 78% of the population, led to a rapid decline in colony abundance. The estimated population growth rate (λ) for the diseased population was more than six times lower than would be expected for a population at equilibrium. It was found that colonies in the smaller size class (≤100cm total linear length) were more likely to get infected and succumbing to the disease than larger colonies. Model simulations indicate that: (1) under the estimated λ, the population would reach extinction in 5 years; (2) an SDR outbreak as intense as the one observed in this study can lead to a notable decline in stochastic λs even when relatively rare (i.e. 10% probability of occurring); and (3) disease incidence as low as 5% can cause the population to lose its ecological functionality (e.g., reach a pseudo-extinction level of 10% of the initial population size) 33 years before disappearing. SDR and probably any other similarly virulent disease could thus be a major driver of local extinction events of A. cervicornis.

Mexico is a country that makes heavy use of the shark populations that inhabit the southern portion of the Northeast Pacific Ocean (NEP). Shark meat has become an essential food source in this country, while shark fins are used to supply traditional Asian markets. In addition to consumptive utilization, charismatic shark species support an ecotourism industry that has gained significance in several tourist resorts across the country. In this concluding chapter, we recap the contents of chapters included in volumes 83 and 85 in the Advances in Marine Biology series. The chapters in these volumes address biodiversity, conservation genetics, trophic ecology, migratory movements, fisheries, and shark ecotourism, allowing us to understand the state of knowledge relevant to human: shark interactions in the Mexican Pacific. We discuss the challenges for the sustainable use and conservation of sharks in the southern NEP and highlight the need for a more holistic management approach that includes economic and social factors. To meet these challenges, we recommend updating the Mexican National Plan of Action for Sharks published in, 2004, such that it may continue serving as a roadmap for the conservation and management of sharks in the southern NEP during the years to come.

Sharks have been of great cultural and socioeconomic importance in Mexico since the late 19th century, when the first fisheries were prosecuted in the Gulf of California to export fins to China. Mexican shark and ray fisheries are classified mainly by the size of the fishing vessel and include small- (7.5-10m), medium- (10-27m), and large-sized (>27m) fisheries. All are multispecies fisheries that use longline or gillnet gear, with their relative productivity varying over time. Off the Pacific coast, early shark small size vessel fisheries in the Gulf of California were driven by the need for vitamin A from livers, especially during World War II. As this fishery declined, new shark fishing opportunities arose because of government support and the development of the medium-sized fishery, which was capable of farther offshore excursions. Shark meat became an important part of the diets of poor and impoverished citizens during the 1950s and 1960s. The establishment of a Mexican Exclusive Economic Zone in 1976 pushed foreign vessels from Asia out of Mexican waters and led to the development of the large-sized vessel fishery to exploit pelagic sharks in offshore waters. By the early 1980s, Mexico shark fisheries were among the most productive in the world; however, a national economic crisis reduced effort and landings until the late 1980s, when several new fisheries emerged. Landings from Pacific states fluctuated between ~13,000 and 24,000t (dressed weight) during 1987-2012 but expanded steadily thereafter because of government support and offshore fleet expansion. Shark fisheries landings from the Mexican Pacific are currently at their highest recorded levels, exceeding 31,000t; however, a lack of species-specific landings and life history information has precluded population assessments of targeted stocks. In addition, though several recent management measures have been enacted to protect Mexican shark and ray fishery resources, the enforcement of these regulations is severely lacking. Therefore, the long-term sustainability of current fishing levels is unknown but should engender concern based on anecdotal evidence of serial depletion among historical elasmobranch targets in the Mexican Pacific.