Richard S. Appeldoorn

Recent Region-wide Declines in Caribbean Reef Fish Abundance

Profound ecological changes are occurring on coral reefs throughout the tropics, with marked coral cover losses and concomitant algal increases, particularly in the Caribbean region. Historical declines in the abundance of large Caribbean reef fishes likely reflect centuries of overexploitation. However, effects of drastic recent degradation of reef habitats on reef fish assemblages have yet to be established. By using meta-analysis, we analyzed time series of reef fish density obtained from 48 studies that include 318 reefs across the Caribbean and span the time period 1955-2007. Our analyses show that overall reef fish density has been declining significantly for more than a decade, at rates that are consistent across all subregions of the Caribbean basin (2.7% to 6.0% loss per year) and in three of six trophic groups. Changes in fish density over the past half-century are modest relative to concurrent changes in benthic cover on Caribbean reefs. However, the recent significant decline in overall fish abundance and its consistency across several trophic groups and among both fished and nonfished species indicate that Caribbean fishes have begun to respond negatively to habitat degradation.

Sea surface temperatures and coral reef bleaching off La Parguera, Puerto Rico (northeastern Caribbean Sea)

Abstract Much recent attention has been given to coral reef bleaching because of its widespread occurrence, damage to reefs, and possible connection to global change. There is still debate about the relationship between temperature and widespread bleaching. We compared coral reef bleaching at La Parguera, Puerto Rico to a 30-y (1966–1995) record of sea surface temperature (SST) at the same location. The last eight years of the La Parguera SST record have all had greater than average maximum temperatures; over the past 30 y maximum summer temperature has increased 0.7 °C. Coral reef bleaching has been particularly frequent since the middle 1980s. The years 1969, 1987, 1990, and 1995 were especially noteworthy for the severity of bleaching in Puerto Rico. Seven different annual temperature indices were devised to determine the extent to which they could predict severe coral bleaching episodes. Three of these, maximum daily SST, days >29.5 °C, and days >30 °C predict correctly the four years with severe bleaching. A log-log linear relationship was found between SST and the number of days in a given year above that SST at which severe coral beaching was observed. However, the intra-annual relationship between temperature and the incidence of bleaching suggests that no one simple predictor of the onset of coral bleaching within a year may be applicable.

Age determination, growth, mortality and age of first reproduction in adult Queen Conch, Strombus gigas L., off Puerto Rico

Abstract Growth and mortality of adult Strombus gigas L. was studied in a population offshore of La Parguera, Puerto Rico. Adult queen conchs do not grow in shell length, but only in shell thickness. Growth in thickness of the flared shell-lip was measured during a 2-year mark-recapture study and modelled using the von Bertalanffy growth function. Model parameters were K=0.3706 year −1 and L ∞ (asymptotic lip-thickness) =54.9 mm; the third von Bertalanffy parameter, t 0 , cannot be obtained from mark-recapture data alone. Growth in tissue, meat and shell weights of adults were determined using the von Bertalanffy growth function in conjunction with regression equations for weights versus shell length and/or lip thickness. Total instantaneous mortality in adults, determined using von Bertalanffy parameters and lip-thickness frequency analysis, was 1.66 year −1 . Subtracting a previous estimate of fishing mortality ( F =1.14 year −1 ) yielded a natural mortality ( M ) of 0.52 year −1 . Given an average age at maturation, defined by the formation of the flared shell-lip, of 3.2 years, the age of first reproduction was estimated at 3.6 years, but could be as much as 4 years.

Pelagic spawning and egg transport in coral-reef fishes: a skeptical overview

The literature on the pelagic spawning of inshore reef fishes is replete with the idea that individuals spawn at times and specific locations that ensure eggs being swept quickly off reefs and into offshore waters. The choice of spawning times and sites has been hypothesized to function primarily either to minimize egg predation from reef-associated fishes and invertebrates (Johannes 1978), to maximize dispersal (Barlow 1981), or to provide maximum opportunity for pelagic larvae to survive in waters with patchy and irregular distribution of food (Doherty et al. 1985). All of these ideas share two assumptions: that it is advantageous for pelagic eggs and/or larvae to be removed from shallow reefs as quickly as possible, and that this advantage has acted as a selective force to produce specific spawning times and sites. Several behavioral strategies resulting from this selective pressure have been proposed (Randall & Randall 1963, Jones 1968, Ehrlich 1975, Warner et al. 1975, Johannes 1978, Robertson 1983): (1) migrating to the edge of the insular shelf to spawn; (2) spawning at the outer or downstream edges of reefs; (3) spawning from local promontories high in the water column or ejecting gametes at the top of a spawning rush; and (4) spawning during strong local off-reef or offshore currents, e.g. during spring

Length-based assessment of sustainability benchmarks for coral reef fishes in Puerto Rico

SUMMARY The sustainability of multispecies coral reef fisheries is a key conservation concern given their economic and ecological importance. Empirical estimation and numerical model analyses were conducted to evaluate exploitation status via resource reference points (or sustainability benchmarks) for coral reef fishes of the snapper-grouper complex in Puerto Rico. Mean size (¯ L, in length) of animals in the exploited part of the population was estimated from fishery-dependent and fishery-independent size composition data and used as an indicator variable of exploitation rates. In application, fishing mortality rates estimated from ¯ L of various data sources were comparable. Of the 25 reef fish species assessed, 16 were below 30% spawning potential ratio (SPR), six were above 30% SPR, and three could not be reliably determined owing to low sample sizes. These findings indicate that a majority ofsnapper-grouperspeciesinPuertoRicoarecurrently fished at unsustainable levels.

Movement of fishes (Grunts: Haemulidae) across the coral reef seascape: A review of scales, patterns and processes

Abstract. Reef fish movements over short and long time frames have important consequences for identifying essential fish habitat, quantifying ecological flows across the seascape and designing marine reserves. We use grunts (Haemulidae) as a representative model group for quantifying movement in terms of distances, time scales, temporal patterns, habitat associations and controls. Here, we provide a review based on recent studies and our own experience. The ritualized, twilight feeding migrations of grunts represent an important mechanism for transferring nutrients and organic matter across habitat boundaries, with movements on the order of 100–300 m. Both compass orientation and vision are used for navigation during feeding migrations. Feeding movements of adults are less ritualized in both space and time and typically occur on the same scale of distance as juveniles, although longer excursions have been documented. Ontogenetic migrations occur over years and take the form of discrete habitat shifts, with most individuals moving progressively offshore. Distances and pathways followed by fish will depend on the exact width of the shelf and distribution of suitable habitats. Transplant experiments suggest there are significant barriers to fish migration, and migration corridors, especially reef margins, seem to be important in determining the direction of ontogenetic habitat shifts, but these may be disrupted by environmental perturbations. Theoretical considerations relative to barrier perception and growth-survival trade-offs appear to explain normal movements of grunts and their responses to environmental perturbations, but lack of information on how fish may sense new locations at distance prevents the full use of theory to generate rules of migration covering timing, distance and direction.

Theme section on mesophotic coral ecosystems: advances in knowledge and future perspectives

Abstract The Second International Mesophotic Coral Ecosystems (MCEs) workshop was held in Eilat, Israel, October 26–31, 2014. Here we provide an account of: (1) advances in our knowledge of MCE ecology, including the central question of the potential vertical connectivity between MCEs and shallow-water reefs (SWRs), and that of the validity of the deep-reef refugia hypothesis (DRRH); (2) the contribution of the 2014 MCE workshop to the central question presented in (1), as well as its contribution to novel MCE studies on corals, sponges, fish, and crabs; and (3) gaps, priorities, and recommendations for future research stemming from the workshop. Despite their close proximity to well-studied SWRs, and the growing evidence of their importance, our scientific knowledge of MCEs is still in its infancy. During the last five years, we have witnessed an ever-increasing scientific interest in MCEs, expressed in the exponential increase in the number of publications studying this unique environment. The emerging consensus is that lower MCE benthic assemblages represent unique communities, either of separate species or genetically distinct individuals within species, and any significant support for the DRRH will be limited to upper MCEs. Determining the health and stability of MCEs, their biodiversity, and the degree of genetic connectivity among SWRs and MCEs, will ultimately indicate the ability of MCEs to contribute to the resilience of SWRs and help to guide future management and conservation strategies. MCEs deserve therefore management consideration in their own right. With the technological advancements taking place in recent years that facilitate access to MCEs, the prospects for exciting and innovative discoveries resulting from MCE research, spanning a wide variety of fields, are immense.

Catching efficiency and selectivity of gillnets and trammel nets in coral reefs from southwestern Puerto Rico

Abstract A comparative fishing experiment was conducted to investigate the capture efficiency and selectivity of bottom-set gillnets and trammel nets. Twelve gillnets and trammel nets of different mesh sizes (7.6, 8.8, 10.1, and 12.6 cm stretched mesh) and hanging ratios (1:1, 1:2, and 1:3) were fished from May 1990 to September 1991 in coral reef (inner and outer reef) and mangrove areas off La Parguera, Puerto Rico. Significant differences in capture due to mesh size and hanging ratio for the inner and outer reef were observed. However, catches in mangroves were only influenced by hanging ratio. Significant interaction between mesh size and hanging ratio influencing the catches of both gears was found. The interaction behaved in an oppositive manner between the two gears. Largest catches in gillnets were obtained by combination of high hanging ratio (1:3) with large meshes (12.7 cm) or low hanging ratio (1:1) with small meshes (7.6). For trammel nets, the largest catches were obtained with low hanging ratio (1:1) with large meshes (12.7 cm) or high hanging ratio (1:3) with small meshes. This oppositive interaction may arise from the different mode of capture of these gears. Selectivity curves were generated for four species: white grunt ( Haemulon plumieri ), bluestriped grunt ( Haemulon sciurus ), stoplight parrotfish ( Sparisoma viride ) and sea bream ( Archosargus rhomboidales ). The selectivity curves of gillnets and trammel nets were unimodal. Optimum length increases as the mesh size increases, and the selection range becomes wider as hanging ratio increases.

Transforming reef fisheries management: application of an ecosystem-based approach in the USA Caribbean

Fisheries in Puerto Rico and the United States (US) Virgin Islands are predominately dependent on nearshore coral reef ecosystems and have suffered from historical overfishing. The unique characteristics of reef fisheries, including strong habitat dependence, susceptibility to coastal impacts, diffuse landing sites and strong multispecies and multigear interactions suggest that standard approaches to fisheries management, especially those typically considered by the US Regional Fishery Management Councils, would not be applicable. Current management authority is split between local and federal agencies; however, there exists no uniform context and direction to current management initiatives, which results in lost efficiencies and opportunities. Proposed here is a new vision for fisheries management that takes into consideration the local ecological and socioeconomic characteristics of fishing, is compatible with regional resources and capacity, is ecosystem based and targets full stakeholder participation. Only an ecosystem-based approach can lead fisheries management out of the trap of unrealistic data collection and analysis demands, while at the same time refocusing emphasis away from attitudes and practices that promote overfishing. Management must be based on first principles regarding the desired state of the ecosystem and initiate strategies based on these principles. The key management goal is not to maximize fisheries catch, but to maintain the ecosystem in a state that will lead to sustained production. First principles would include maintaining ecosystem integrity and function, protecting all habitats and water quality, applying the precautionary approach, monitoring reference points and recognizing that production has limits. Resulting management tactics include marine reserves (to meet multiple goals), closed spawning aggregations, gear restrictions to maintain trophic balance and habitats, targeted data collection and assessments, adopting co-management practices and using ecosystem or community-based metrics. Fisheries management must fully incorporate the tools, resources and methods available within coastal zone management and other environmental agencies, while standards within those programmes must protect ecosystem health. Implementation will require attending to structural barriers inherent within existing fisheries legislation and regulations, multiple jurisdictions and the current cultures of scientists, managers and fisherfolk. Initial efforts should focus on developing a common language and frame of reference for all stakeholders.

Studies of fish traps as stock assessment devices on a shallow reef in south-western Puerto Rico

Abstract Traditional Antillean arrowhead fish traps were deployed around and on a shallow, 8-ha coral reef of south-western Puerto Rico in two 1987 studies: Study I, 2–18 March, a comparison of 30 trap catches and 30 visual transect counts; Study II, 8 April–18 June, a tag and recapture study of 95 trap hauls. Study I considered model taxa and conditions for calculating effective fishing area (EFA) of the traps on the basis of catch per haul and fish density from transects. Of the 185 fish of 24 species caught, EFA could only reasonably be calculated for three taxa: redband parrotfish, Sparisoma aurofrenatum , 25 m 2 and 90 m 2 ; stoplight parrotfish, Sparisoma viride , 24 m 2 ; ocean surgeon, Acanthurus bahianus , 93 m 2 . Other taxa were considered unsuitable because of near-zero density or catche, e.g. white grunt, Haemulon plumieri , was often caught but seldom seen. Ability to assess EFA depended on trap location; future surveys of reef fishes will necessarily have to utilize stratified sampling based on habitat characteristics. Study II considered fish movements within a five-trap, cross-shaped array deployed on a back reef area. Of 702 captures from 28 species, redband parrotfish, white grunt and ocean surgeon dominated. Of 272 fish tagged, 65 were recaptured once and 24 were recaptured twice or more. In the short term, traps seemed to sample a discrete population. Except for one individual, all tagged fish were recaptured at the same trap or at a nearby trap of the array, i.e. no more than 25 or 35 m away; ocean surgeon were always caught at the trap where tagged. Using the mark-recapture data, population estimates were calculated for dominant species. These were not used to estimate EFA because the area sampled by the traps could not be reliably estimated. However, properly designed marking studies could be used to obtain this information. It was concluded that using EFA in trap-based assessments is a promising technique for residents like redband parrotfish or ocean surgeon. Mark and recapture techniques may also return useful density estimates for cryptic or diurnally migrating residents such as white grunt.