Nursery

A brand new, innovative floating coral fish breeding nursery is being tested at the Dive Friends Sand Dollar location on Bonaire.  This project, led by the startup company RoffaReefs, hopes to improve local coral reef fish populations to enhance the overall coral reef health for the Bonaire National Marine Park.

RoffaReef Floating Nursery. Photo credit: Casper Douma

Coral reefs are extraordinarily dynamic yet fragile ecosystems.  From the microorganisms working to build the reef’s foundation to the more recognizable reef inhabitants at the top of the food chain, this diverse ecosystem faces an incalculable number of threats. It is widely known that globally, reefs are struggling to keep up with the changes due to climate change and increased human activity. Sander van Lopik of RoffaReefs has a unique approach to help strengthen coral reefs in the future.

Photo credit: Casper Douma

Floating Fish Nursery

As part of the larger World Wide Fund for Nature the Netherlands (WWF-NL) “Dutch Caribbean Marine Strategy”, RoffaReefs has designed a system to breed marine fish larvae both in controlled aquarium environments and in the wild. Founded in the Rotterdam Zoo Diergaarde Blijdorp, RoffaReefs will begin testing its fish breeding system in the Bonaire National Marine Park through the use of a floating fish nursery. The goal of this project is to strengthen the overall health of the coral reefs by bolstering the local fish populations. Reef fish help maintain balance throughout the coral reefs as herbivorous fish graze on algae which would otherwise smother the coral while carnivorous fish aid in keeping overall populations in balance.

The floating fish nursery is being tested at the Dive Friends Sand Dollar location along the western coast of Bonaire. Throughout the pilot study, data will be collected to aid in improving the breeding system for the next series of trials. This research is a collaborative effort involving WWF-NL, the Dutch Caribbean Nature Alliance (DCNA), STINAPA, TU Delft, Diergaarde Blijdorp and KKV lijn in water B.V.

DCNA office lab. Photo credit: Casper Douma

DCNA-office lab

During the project, the researchers have their laboratory set-up at the DCNA office on Bonaire. Here, they are bringing fish eggs to determine the species. The goal is to develop an automatic imagery recognition tool to recognize the species with the ultimate goal to develop a “fish spawning calendar” so we know when and where fish species reproduce during the year.

Future

Projects, such as the RoffaReefs fish nursery, can contribute to healthier coral reefs which is important amongst others for local fisheries, tourism, and to mitigate the effects of sea level rise and worsening storm conditions.

Stay up to date on the projects latest developments by following along with the RoffaReefs Facebook page https://www.facebook.com/RoffaReefs/ or by signing up for the DCNA monthly newsletter BioNews (https://dcnanature.org/news/).

Photo credit: Casper Douma

Published in BioNews 59

Abstract Coral reefs are some of the most diverse and valuable ecosystems worldwide. Since the 1970’s the coral populations of Acropora spp. around Bonaire Island have been declining due to White Band Disease (WBD) and due to heavy storms and hurricanes (i.e., hurricane Lenny in 1999). Acropora cervicornis is one of the species selected as restoration target because its critically endangered status according to the IUCN red list and its ecological value as reef builder. Promoting genetic diversity is key to aid the recovery of degraded populations and give this species higher chance to survive in the long-term. In this study, we measure growth and healing, as phenotypic traits of propagated corals to assess the different genotype performance in the nursery phase. Linear length and tissue regeneration have been monitored for 8 weeks for 10 different genotypes (n=5), respectively with in situ measurement and image analysis. The preliminary results suggest that some individual fragments can grow up to one centimeter per week and achieve complete tissue regeneration from cutting and handling damage in 15 days. Being able to determinate the differences in performance from various coral genotypes can help nursery based coral restoration to be more performant. Indeed, selecting coral genotypes that can grow and regenerate faster is a considerable advantage for coral restoration practitioners that could therefore optimize their outplanting efforts.

Jr Ranger presentation about the importance of mangroves and seagrasses.

Various species of aquatic animals have complex life cycles and utilize different habitats during consecutive phases of their life cycles. For example, many marine fish species occupy different habitat types during juvenile and adult life stages. Juveniles of some species recruit to inshore nursery habitats such as mangroves and seagrass beds, whereas large adults tend to dominate coral reefs. The mechanisms underlying apparent cross-habitat distribution patterns by life stage remain uncertain for many species. Here, we investigated potential mechanisms that produce a 5-phase, and possibly even a 6-phase life cycle pattern in a common Caribbean coral reef fish species Haemulon flavolineatum (French grunt) across multiple coastal habitats. At each discrete life stage, individuals were faced with important and stage-specific ecological trade-offs that could significantly augment fitness. Pelagic larvae settled on rubble habitats near bay entrances where they reached an optimum between predation risk (survival) and food abundance (growth). Individuals subsequently shifted to seagrass beds, likely as a result of increased food resources, followed by a shift to mangroves as predation refugia. Before the uni-directional movement between bays and coral reefs, some fishes shifted from mangroves to boulder/notch habitats. Likely, this habitat serves as an intermediate stop before their final shift to the coral reef, where they reach maturity and reproduce. This study reveals ecological linkages and flows among habitat types that are of direct conservation importance to these ecosystems. Furthermore, the identification of mechanisms that give rise to cross-habitat distribution patterns of marine fishes in general might lead to enhanced conservation management solutions to declines in fisheries at larger scales. 

Abstract

The importance of mangrove and seagrass lagoonal habitats as nursery areas for many reef-associated fish species is well established in the scientific literature. However, few studies have examined the relative use by nursery species of different sub-habitats within such systems. Here, we investigated fish community structure of a variety of interconnected sub-habitats of the tropical lagoon of Lac Bay in Bonaire, Dutch Caribbean. Visual census was used to test the degree to which these sub-habitats may differ in their use by fishes of different species and life stages. We quantitatively sampled the fish species abundance, composition, and size structures at a total of 162 sites distributed among nine different sub-habitats that are common to mangrove and seagrass ecosystems. Fish community variables differed consistently among sub-habitats and were mainly influenced by the presence of mangrove root structure or seagrass cover. Mangrove fringe sub-habitats were a premier habitat since multiple life stages of a variety of species showed highest densities and biomass there. Several reef fish species had a distribution pattern suggesting a unique stepwise post-settlement life cycle migration in which larger juveniles and/or subadults appear to move from the open bay environment (seagrass beds or bay mangrove fringe) to the interior mangrove fringes along mangrove pools before later departing to the adult habitat of the coral reef. In the case of the well-lit and well-circulated central bay sub-habitat, the limiting factor to fish abundance and diversity appeared to be the paucity of three-dimensional shelter due to the lack of Thalassia seagrass beds. In the warm and hypersaline backwaters, physiological tolerance limits were likely a key limiting factor. Long-term changes driven by mangrove expansion into this non-estuarine lagoon have been steadily reducing the net coverage of clear bay waters, while the surface of shallow, muddy, and hypersaline backwaters, unusable by key nursery reef fish species, has been increasing by an almost equal amount. Our study shows how fish density varies along the full gradient of sub-habitats found across a tropical bay to provide insight into the potential consequences for nursery habitat function when the availability and quality of these sub-habitats change in response to the long-term dynamic processes of mangrove land reclamation and climate change.

The rainbow parrotfish Scarus guacamaia has an obligate dependence on man- groves at juvenile stages, and, as the largest herbivorous fish in the Caribbean region, its distribution has important implications for coral reefs. The effect of connectivity with mangroves on relative density, biomass and size of S. guacamaia was assessed from over 65 km of visual sur- veys from Bonaire, Caribbean Netherlands. In addition, an individual-based, age-structured, mechanistic model (IBM) was developed to explain dispersal patterns from nurseries for S. guaca- maia. In the IBM, mortality was constant, growth was determined by a von Bertalanffy growth equation, and movement was modeled through a random walk process. Using the IBM, simula- tions were run to generate patterns of density, biomass, and size with distance from nurseries. Rainbow parrotfish were observed as far as 42 km away from the nearest mangroves on Bonaire. Relative density and biomass showed significant exponential declines with distance from the pri- mary mangrove nursery and were significantly higher in high versus low complexity non-man- grove habitats. Mean size increased linearly with distance (r2 = 0.74), reflecting an absence of smaller individuals with greater distance. These results were closely mirrored by the simulation study: density and biomass declined exponentially with distance from nurseries, and size and age increased following saturating functions. The results suggest that mangroves may have the poten- tial to supply individuals much further than previously thought. Both the empirical and simulation studies reaffirm calls to prioritise protection of reef habitats close to nurseries as well as the nurseries themselves.