Unravelling seascape patterns of cryptic life stages: non-reef habitat use in juvenile parrotfishes

Juvenile fish often use alternative habitats distinct from their adult phases. Parrotfishes are an integral group of coral reef fish assemblages, are targeted in fisheries, are sensitive to reef disturbances, and have been documented as multiple-habitat users. Considering the abundance of research conducted on parrotfishes, very little is known about their juvenile ecology at the species level due to their cryptic and variable coloration patterns. We collected juvenile parrotfishes in non-reef habitats (macroalgal beds, seagrass beds, and lagoons) in the Philippines and used DNA analysis to determine species composition. The results were then compared with data on adult parrotfish abundance from underwater visual census (UVC) surveys in coral reef and non-reef habitats. Collections identified 15 species of juvenile parrotfishes in non-reef habitats, and of these, 10 were also recorded in UVCs as adults. Informed by adult surveys, 42% of the 19 parrotfish species observed as adults were classified as multi-habitat users based on their presence in coral reef and non-reef habitats. When accounting for the occurrence of species as juveniles in non-reef habitats, 93% of the species collected as juveniles would be considered multi-habitat users. Species identified as juveniles in non-reef habitats comprised 50% of the average adult parrotfish density on coral reefs and 58–94% in non-reef habitats. The species richness of juveniles in non-reef habitats was greater than that of adults occupying the same habitats, and the most common adult species observed in UVCs was not collected as juveniles in non-reef habitats. Finally, UVC suggested that 97% of juvenile parrotfish <10-cm total length was present in non-reef habitats compared to coral reefs. These results provide further evidence for ontogenetic movement across habitat boundaries for parrotfish species in a diverse and highly connected tropical seascape. This is one of the few studies to quantify links between nursery and adult habitat in parrotfishes, highlighting the importance of including non-reef habitats in ecological studies of an iconic group of coral reef fish

Fishing pressure impacts the abundance gradient of European lobsters across the borders of a newly established marine protected area

Marine protected areas (MPAs) are considered viable fisheries management tools due to their potential benefits of adult spillover and recruitment subsidy to nearby fisheries. However, before–after control–impact studies that explore the biological and fishery effects of MPAs to surrounding fisheries are scarce. We present results from a fine-scale spatial gradient study conducted before and after the implementation of a 5 km2 lobster MPA in southern Norway. A significant nonlinear response in lobster abundance, estimated as catch-per-unit-effort (CPUE) from experimental fishing, was detected within 2 years of protection. After 4 years, CPUE values inside the MPA had increased by a magnitude of 2.6 compared to before-protection values. CPUE showed a significant nonlinear decline from the centre of the MPA, with a depression immediately outside the border and a plateau in fished areas. Overall fishing pressure almost doubled over the course of the study. The highest increase in fishing pressure (by a magnitude of 3) was recorded within 1 km of the MPA border, providing a plausible cause for the depression in CPUE. Taken together, these results demonstrate the need to regulate fishing pressure in surrounding areas when MPAs are implemented as fishery management tools.publishedVersio

The contribution of macroalgae-associated fishes to small-scale tropical reef fisheries

Macroalgae-dominated reefs are a prominent habitat in tropical seascapes that support a diversity of fishes, including fishery target species. To what extent, then, do macroalgal habitats contribute to small-scale tropical reef fisheries? To address this question we: (1) Quantified the macroalgae-associated fish component in catches from 133 small-scale fisheries, (2) Compared life-history traits relevant to fishing (e.g. growth, longevity) in macroalgal and coral-associated fishes, (3) Examined how macroalgae-associated species can influence catch diversity, trophic level and vulnerability and (4) Explored how tropical fisheries change with the expansion of macroalgal habitats using a case study of fishery-independent data for Seychelles. Fish that utilised macroalgal habitats comprise 24% of the catch, but very few fished species relied entirely on macroalgal or coral habitats post-settlement. Macroalgal and coral-associated fishes had similar life-history traits, although vulnerability to fishing declined with increasing contribution of macroalgae association to the catch, whilst mean trophic level and diversity peaked when macroalgal-associated fish accounted for 20%-30% of catches. The Seychelles case study revealed similar total fish biomass on macroalgal and coral reefs, although the biomass of primary target species increased as macroalgae cover expanded. Our findings reinforce that multiple habitat types are needed to support tropical fishery stability and sustainability. Whilst coral habitats have been the focus of tropical fisheries management, we show the potential for macroalgae-associated fish to support catch size and diversity in ways that reduce vulnerability to overfishing. This is pertinent to seascapes where repeated disturbances are facilitating the replacement of coral reef with macroalgal habitats

The Fisheries Co-Management Guidebook: Emerging research for the effective management of small-scale fisheries

Small-scale fisheries account for 40% of global fish catch and employ more than 90% of the world’s fishers, defining the livelihoods, nutrition, and culture of a substantial and diverse segment of humankind. In recent decades collaborative forms of fisheries management, including co-management, have gained popularity as the most appropriate, fair, and effective form of governance for small-scale fisheries. Fisheries co-management is envisioned as a process by which to reverse the interconnected crises of hunger, poverty, and biodiversity loss, transforming small-scale fisheries into engines of prosperity, inclusion, and sustainability. Yet co-management can succeed or fail, and implementation does not mean positive impacts for food security, nutrition, livelihoods, or biodiversity. Nor does it imply programs will respect human rights, gender equality, or principles of justice and equity. Fewer management programs implemented well might achieve far more than many implemented poorly, and poorly implemented co-management can be worse than no management. This guide was designed to assist practitioners in understanding the latest research on what constitutes successful fisheries co-management, and how to reach this objective. The aim is to synthesize emerging research that, if adopted, would substantially improve impacts across both ecological and social dimensions. The guide is presented as an infographic series with each infographic summarizing a substantial body of research from a particular field. This work was undertaken through a growing partnership between the Wildlife Conservation Society and WorldFish, aiming to increase collaboration between conservation and development sectors. This partnership represents a milestone towards integrated approaches for the benefit of both ecosystems and local communities

A field and video-annotation guide for baited remote underwater stereo-video surveys of demersal fish assemblages

Researchers TL, BG, JW, NB and JM were supported by the Marine Biodiversity Hub through funding from the Australian Government's National Environmental Science Program. Data validation scripts and GlobalArchive.org were supported by the Australian Research Data Commons, the Gorgon-Barrow Island Gorgon Barrow Island Net Conservation Benefits Fund, administered by the Government of Western Australia and the BHP/UWA Biodiversity and Societal Benefits of Restricted Access Areas collaboration.1. Baited remote underwater stereo-video systems (stereo-BRUVs) are a popular tool to sample demersal fish assemblages and gather data on their relative abundance and body-size structure in a robust, cost-effective, and non-invasive manner. Given the rapid uptake of the method, subtle differences have emerged in the way stereo-BRUVs are deployed and how the resulting imagery are annotated. These disparities limit the interoperability of datasets obtained across studies, preventing broad-scale insights into the dynamics of ecological systems. 2. We provide the first globally accepted guide for using stereo-BRUVs to survey demersal fish assemblages and associated benthic habitats. 3. Information on stereo-BRUV design, camera settings, field operations, and image annotation are outlined. Additionally, we provide links to protocols for data validation, archiving, and sharing. 4. Globally, the use of stereo-BRUVs is spreading rapidly. We provide a standardised protocol that will reduce methodological variation among researchers and encourage the use of Findable, Accessible, Interoperable, and Reproducible (FAIR) workflows to increase the ability to synthesise global datasets and answer a broad suite of ecological questions.Publisher PDFPeer reviewe

Patterns and mechanisms of spillover from marine reserves

The use of no-take marine reserves (areas closed to fishing) as fishery management tools has been advocated considerably in the past decade. No-take reserves are now often established with an objective of enhancing fisheries. However, the fishery effects of no-take reserves remain controversial. Spillover, or net export of adult biomass, is one potential process of fisheries enhancement by reserves. Few studies have shown convincingly that reserves can develop spillover that benefits local fisheries. The objective of this thesis was to investigate the predicted patterns and proposed mechanisms of spillover from no-take reserves. The no-take reserves studied were on coral reefs in the Philippines that have been well protected for 15 to 20 years. In the first study, I tested the prediction that gradients of decreasing abundance of target species, from high inside the reserve to low outside, would be present across the boundaries of no-take reserves. Spillover is predicted to produce such patterns. Underwater visual census of fishes was carried out along large transects (each one approximately 1 km long) that crossed the lateral boundaries of each of two no-take reserves and two controls (fished sites) at each of two islands. Patterns of decreasing abundance (density and biomass) of target fishes were found only across one boundary of one no-take reserve, the reserve at Apo Island (Apo Reserve). The patterns of decreasing abundance were limited to within 50-200 m of the boundary. Rates of decrease in abundance across the boundary were two to three times greater for sedentary fishes than for vagile fish. This finding is consistent with the expectation that the spatial extent of spillover would vary according to mobility of fishes. The patterns of decreasing abundance of target fishes were probably not due to gradients in habitat. Furthermore, no pattern of decreasing abundance across the boundary was found for fishes not targeted by fisheries.\ud \ud \ud In the second study, I investigated the potential mechanisms inducing movement of a targeted planktivorous reef fish, Naso vlamingii, from Apo Reserve to adjacent fished areas. Repeated underwater visual census at reserve and fished sites suggested that some adults of N. vlamingii could emigrate temporarily from Apo Reserve within the short-term (days). Data from visual census and experimental hook and line fishing suggested that short-term emigration of N. vlamingii is related to movement to feeding areas 150-200 m away from reserve boundaries. However, some larger (41-45 cm TL) adults probably tend to stay inside the reserve. Experimental hook and line fishing adjacent to the reserve also showed that the mean size of N. vlamingii captured decreased as one mo ved up to 300 m away from the boundaries of Apo Reserve. This pattern may have resulted from density-dependent home range relocation of smaller adult N. vlamingii over the long term. Competitive interactions between adult N. vlamingii were up to twice as frequent, on a per fish basis, inside the reserve than outside. When interacting adults differed in sizes, the larger adult was always observed to chase away the smaller one. The sizes of adults that were chased away (25-35 cm TL) were similar to the sizes of those caught by experimental fishing (26-38 cm TL). In the third study, I attempted to quantify the contribution of spillover to the yield of the local fishery at Apo Island. Daily fishing effort and yield (biomass and value) of local fishers in relatio n to Apo Reserve were studied for eight months (July 2003 to February 2004) over two monsoonal seasons. Average catch rates and income rates of fishers were found to be highest near the reserve (within 300 m of reserve boundaries). Catch rates near the reserve were higher than in other areas far from the reserve by a factor of 1.1 to 2.0, depending on the fishing gear. Moreover, the highest average monthly catch rates were always found near the reserve. These findings are consistent with occasional very large catches near the reserve due to spillover. However, fishing effort was often lowest near Apo Reserve. Furthermore, local fishers seemed to have avoided fishing very close to the reserve (within 100 m of reserve boundaries). Most fishing (79% of overall fishing effort) occurred far from the reserve, on the northern fishing grounds of Apo Island. Yields from spillover probably contributed less than 10% of the total yield of the local fishery. Fishing effort near Apo Reserve appears to be limited by 1) weather conditions caused by the monsoons, 2) the traditional importance of the northern fishing grounds, 3) high variability of catch rates and income rates, 4) lower value of target species found near the reserve, and 5) social pressures within the local community. \ud \ud The results of this thesis provide consistent, yet equivocal, evidence for spillover from Apo Reserve. This study could not provide information on patterns of abundance (density, biomass, mean size or catch rate) and behaviour (movement and aggressive interactions) of target fishes, nor patterns of fishing effort of fishers, before the reserve was established. Nonetheless, research over the last two decades suggests that spillover of target fishes from Apo Reserve has developed over time. Spillover may have produced some of the patterns found in the present study. The main conclusion from this thesis is that Apo Reserve has probably developed spillover, but has provided very limited direct benefits to the local fishery

Replenishment and connectivity of reef fish populations in the central Philippines

The dynamics of reef fish populations at lower latitudes are not well understood, particularly in the Coral Triangle (composed of the Philippines, Malaysia, Indonesia, Timor Leste, Papua New Guinea and the Solomon Islands), where the monsoons (shifting tradewinds) are potential drivers of seasonality of reproduction and recruitment. Such dynamics will also be influenced by the degree to which local populations self-replenish or rely on larval replenishment from other populations. However, few have investigated the effects of the monsoons on the replenishment of reef fish populations. Furthermore, the extent of ecologically-significant larval dispersal of reef fishes, in general, remains unclear. Understanding the patterns and key processes behind population replenishment and larval dispersal are critical to the application of no-take marine reserve networks as conservation and fisheries management tools. This thesis addresses knowledge gaps about the patterns of reproduction, recruitment and larval connectivity of reef fish populations in the central Philippines, the epicentre of reef fish biodiversity in the Coral Triangle.\ud \ud The questions that this thesis addresses are especially relevant to the use of notake marine reserves for reef conservation and fisheries management in the Philippines, a developing archipelagic nation with a vast coral reef area, a large and rapidly growing human population and a great number of small, community-based marine reserves. Most coastal communities in the Philippines are poor and have few employment alternatives. Many communities rely on coral reefs for food and livelihood. No-take marine reserves in the Philippines are regarded as a viable option to conserve and manage coral reefs that is acceptable to local stakeholders.\ud \ud This thesis consists of four related studies. In the first study, I tested the prevailing notion that spawning peaks of reef fish at lower latitudes are timed to take advantage of weaker winds during inter-monsoonal periods, supposedly to limit advection and enhance survivorship of larvae. The monthly spawning patterns of four species of reef fish (2 fusiliers, 1 surgeonfish and 1 damselfish) were studied for 11-22 months. All four species showed protracted spawning periods. However, results suggested that the monsoons affect reproduction in ways that are not consistent with the above hypothesis. Conditions advantageous to larval survival may not be restricted to the inter-monsoonal periods. An alternative explanation is that the spawning patterns probably reflected temperature, rainfall, wind or wave action more directly influencing the spawning of adults, as opposed to adaptation of the timing of reproduction to ensure higher survivorship of larvae in the pelagic environment. The complex effects of the monsoons on reproduction in reef fishes warrant further study.\ud \ud In the second study, I investigated the patterns of recruitment (larval settlement) of 120 species of reef fish almost every month for 20 consecutive months at two island and two coastal locations. Recruitment was found to occur throughout the year. Most species exhibited protracted recruitment seasons (up to 9-11 months). However, a predictable annual peak in community-wide recruitment of reef fishes was detected, coinciding with the weakening of monsoon winds and higher sea surface temperature. The annual pattern of recruitment was fairly consistent across 11 sites and between the two years sampled. The same recruitment pattern was also found in the two families that dominated monthly recruitment to reefs, the damselfishes and the wrasses, notwithstanding a 10-fold difference in overall abundance of recruits of these two families. These findings implied a far-reaching influence of the monsoons on recruitment of reef fishes at lower latitudes.\ud \ud In the third study, I determined the extent of potential larval connectivity among reef fish populations across a 300-km-wide region of the Bohol Sea in the central Philippine archipelago, by combining two very different methods: 1) analysis of species assemblage patterns (presence/absence of 216 species at 61 sampling sites) and associated habitat patterns; and 2) modelling of reef fish larval dispersal patterns. The results of the two methods independently suggested probable connectivity within a large group of sites situated in an internal sea where a dominant westward current is present. The presence of potentially significant connectivity among these sites, and their lack of strong connectivity with other sites were probably strongly influenced by the local oceanographic setting and habitat. The results were consistent with present knowledge of the spatial scales of ecologically-relevant larval dispersal in reef fishes (10's of kilometres). The study provided a framework for connectivity within existing networks of no-take marine reserves in the region.\ud \ud In the final study, I estimated the probable extent of recruitment subsidy (net larval export) and larval connectivity of 39 small (< 1 km2) no-take marine reserves within a more limited (135 x 70 km) region of the Bohol Sea in the central Philippines. The reserves were estimated to occupy about 6% of total reef area in that region. I used a simple exponential model of population recovery to estimate the increase in larval production of large predatory reef fishes inside reserves over time. Larval dispersal and recruitment were simulated using a larval dispersal model. The model simulations showed that a 3.5-fold (~250%) increase in recruitment to fished areas may result from a 55-fold increase in larval production inside reserves if all reserves were effectively protected for 20 years. Lesser larval subsidies are likely to more than replace losses in yield due to reserve creation but they will be difficult to detect because of temporal and spatial variation in recruitment. The strength of larval connectivity between reserves increased dramatically (up to ~20-fold) with greater larval production. These findings highlight the importance of protecting reserves over the long-term (decades) and establishing reserve networks that interact effectively via larval exchange in order for reserves to sustain reef fisheries in highly overfished areas and the reserve networks of which they are a part.\ud \ud A synthesis of the results of this thesis highlighted the importance of the monsoons and local geographic setting in shaping the patterns of replenishment and connectivity of reef fish populations in the Coral Triangle. The implications of potential relationships between the monsoons and the dynamics of reef fish populations amidst a changing climate were also explored. Finally, future research that can validate ecologically-relevant larval connectivity within reserve networks and encourage the long-term protection of reserves were proposed

Fish in a man-made lake: what is there to eat? (Ecological studies in La Mesa Reservoir)

Abstract only.Since 1975, a number of ecological studies have been done in La Mesa Reservoir (also known as La Mesa Dam or La Mesa Lake). Eight species of fish are known to occur in the lake; of these species, one is stocked to control the proliferation of algae. The plankton community of the reservoir has been found to be remarkably diverse, with at least 62 species of zooplankton and possibly 70 species of phytoplankton. The high biological diversity is due to this lake being a protected area as it is Metro Manila's main source of drinking water. A confluence of several factors that preserve this condition of high aquatic biodiversity is possible: (1) Little perturbation in its water quality and its watershed occurs. (2) During high water levels, numerous coves and embayments and the moderate depths create a myriad of ecological niches and refuges for the aquatic biota. (3) Plankton diversity is likely enhanced by abundance of edible algal species (for herbivorous zooplankton) and only occasional moderate algal blooms. (4) Low fish predation tolerates large-sized species in the plankton, i.e., Filipinodiaptomus insulanus, a copepod endemic to only a few large areas in Luzon. (5) Nuisance algae are controlled by stocking of tilapia fry and the occasional use of algicide (CuSO4)

Density-dependent spillover from a marine reserve: long-term evidence

Spillover, the net export of adult fish, is one mechanism by which no-take marine reserves may eventually have a positive influence on adjacent fisheries. Although evidence for spillover has increased recently, mechanisms inducing movement of adult fish from reserve to fished areas are poorly understood. While density-dependent export is a reasonable expectation, given that density of fish targeted by fisheries should increase over time inside well-protected no-take reserves, no study to date has demonstrated development of the process. This study provides evidence consistent with density-dependent export of a planktivorous reef fish, Naso vlamingii, from a small no-take reserve (protected for 20 years) at Apo Island, Philippines. Mean density of N. vlamingii increased threefold inside the reserve between 1983 and 2003. Density approached an asymptote inside the reserve after 15–20 years of protection. Modal size in the reserve increased from 35 to 45 cm total length (TL) over 20 years of protection. In addition, both density and modal size increased outside the reserve close to (200–300 m), but not farther from (300–500 m), the reserve boundary over the 20 years of reserve protection. Movement of adult N. vlamingii across the boundaries of the reserve was rare. Aggressive interactions among adult N. vlamingii were significantly higher (by 3.7 times) inside than outside the reserve. This suggests that density-dependent interactions were more intense inside the reserve. When interacting adults differed in size, the larger individual usually chased away the smaller one. Furthermore, the mean size of adult fish captured by experimental fishing decreased from 35-cm TL 50– 100 m outside the boundary, to 32-cm TL 250–300 m outside the boundary. This represents some of the best evidence available for density-dependent home-range relocation of fish from a no-take reserve