Isolated reefs support stable fish communities with high abundances of regionally fished species

Anthropogenic impacts at isolated and inaccessible reefs are often minimal, offering rare opportunities to observe fish assemblages in a relatively undisturbed state. The remote Rowley Shoals are regarded as one of the healthiest reef systems in the Indian Ocean with demonstrated resilience to natural disturbance, no permanent human population nearby, low visitation rates, and large protected areas where fishing prohibitions are enforced. We used baited remote underwater video systems (BRUVS) to quantify fish assemblages and the relative abundance of regionally fished species within the lagoon, on the slope and in the mesophotic habitat at the Rowley Shoals at three times spanning 14 years and compared abundances of regionally fished species and the length distributions of predatory species to other isolated reefs in the northeast Indian Ocean. Fish assemblage composition and the relative abundance of regionally fished species were remarkably stable through time. We recorded high abundances of regionally fished species relative to other isolated reefs, including globally threatened humphead Maori wrasse (Cheilinus undulatus) and bumphead parrotfish (Bolbometopon muricatum). Length distributions of fish differed among habitats at the Rowley Shoals, suggesting differences in ontogenetic shifts among species. The Cocos (Keeling) Islands typically had larger‐bodied predatory species than at the Rowley Shoals. Differences in geomorphology, lagoonal habitats, and fishing history likely contribute to the differences among remote reefs. Rowley Shoals is a rare example of a reef system demonstrating ecological stability in reef fish assemblages during a time of unprecedented degradation of coral reefs.     

Evidence of artisanal fishing impacts and depth refuge in assemblages of Fijian reef fish

Protection from fishing generally results in an increase in the abundance and biomass of species targeted by fisheries within marine reserve boundaries. Natural refuges such as depth may also protect such species, yet few studies in the Indo Pacific have investigated the effects of depth concomitant with marine reserves. We studied the effects of artisanal fishing and depth on reef fish assemblages in the Kubulau District of Vanua Levu Island, Fiji, using baited remote underwater stereo-video systems. Video samples were collected from shallow (5–8 m) and deep (25–30 m) sites inside and outside of a large old marine reserve (60.6 km², 13 years old) and a small new marine reserve (4.25 km², 4 years old). Species richness tended to be greater in the shallow waters of the large old reserve when compared to fished areas. In the deeper waters, species richness appeared to be comparable. The difference in shallow waters was driven by species targeted by fisheries, indicative of a depth refuge effect. In contrast, differences in the abundance composition of the fish assemblage existed between protected and fished areas for deep sites, but not shallow. Fish species targeted by local fisheries were 89% more abundant inside the large old reserve than surrounding fished areas, while non-targeted species were comparable. We observed no difference in the species richness or abundance of species targeted by fisheries inside and outside of the small new reserve. This study suggests that artisanal fishing impacts on the abundance and species richness of coral reef fish assemblages and effects of protection are more apparent with large reserves that have been established for a long period of time. Observed effects of protection also vary with depth, highlighting the importance of explicitly incorporating multiple depth strata in studies of marine reserves.     

Decadal Changes in the Abundance and Length of Snapper (Chrysophrys auratus) in Subtropical Marine Sanctuaries

Abundance and length of the highly-targeted snapper Chysophrys auratus were compared between sites in ''no take'' areas (Sanctuary Zones: SZ), partial protected areas which are fished (Habitat Protection Zones: HPZ), and areas outside (Outside) the Solitary Islands Marine Park (SIMP), Australia. Baited Remote Underwater Video (BRUV) sampling on shallow rocky reef (15 - 25 m) was conducted annually from 2002 until 2014 in the Austral-winter, covering the decade after these marine park zones were established (2002). Additional deeper sites (25 - 40 m) were sampled in 2010-2011 to assess if findings were more-broadly applicable. Lengths were measured using stereo-BRUVs from 2011-2014. Snapper were significantly more abundant in SZ overall and in most years compared with the other two management types, which did not significantly differ. Snapper rapidly increased after 2 - 3 years protection in all management types, especially SZ. Snapper were present on more SZ deployments than HPZ and Outside after the same period. The positive SZ response in snapper abundance on shallower reef was also found at a broader spatial scale on deeper sites. Again the two fished management types did not show significant differences among each other. There was considerable variation in snapper abundance between years, with strong peaks in 2005, 2009 and 2014 especially in SZ. Abundances remained higher in SZ in the year or two following a strong peak, but decreased to similar abundances to fished areas before the next peak. Snapper length frequency distribution significantly differed between SZ and both fished management types, with more larger snapper within SZ including a higher proportion (58%) that were legal-sized (>25.7 cm FL). HPZ and Outside did not significantly differ from each other, and were dominated by individuals below legal size. Overall, SZ''s have positively influenced abundance and length of snapper on these subtropical rocky reefs.     

Differences in recreationally targeted fishes between protected and fished areas of a coral reef marine park

Many comparisons have been made between sanctuary (no-fishing) and fished areas, where fishing pressure is exerted by artisanal or commercial fishers, but few have examined the effect of recreational fishing on fish assemblages in coral reef habitats. In this study, we compared assemblages of targeted fish from coral reef habitats in sanctuary (no-fishing) and recreationally fished zones of a marine protected area (MPA). Surface visual census (SVC) transects were conducted two times, at three regions, to compare the composition of predatory fish assemblages and the abundance, biomass, and size of the most commonly targeted fish. Baited remote underwater video (BRUV) was used to make relative counts of fish between zones. We also measured benthic cover and rugosity, which may influence fish assemblages. Analysis of similarity (ANOSIM) revealed significant differences in the composition of fish families/genera targeted by fishers (Lethrinidae, Lutjanidae, Haemulidae, Serranidae, and the genus Choerodon of the family Labridae) in terms of biomass (P<0.01) and abundance (P<0.05). The most consistent trends were recorded for biomass and this was supported by clustering of replicates in nonmetric multidimensional scaling (nMDS) ordinations. Similarity percentages (SIMPER) analysis indicated that the family Lethrinidae accounted for 73% (as abundance), and up to 69% (as biomass), of the dissimilarity between zones. Three-factor ANOVA highlighted significantly greater biomass, size, and abundance of legal-sized lethrinids (the most targeted family in the region) in sanctuary zones, but no differences in other families/genera. Results of BRUV supported SVC with greater relative counts of lethrinids (P<0.01) in sanctuaries, but no significant differences for other families. Cover of Acropora coral and hard substrate differed between zones at some regions but differences were inconsistent. There were no significant differences in algal cover or rugosity between zones. Given the inconsistency in benthic cover, the similarity of rugosity between zones, the consistently greater biomass of lethrinids in sanctuaries, and the abundance of large lethrinids in sanctuaries, the cessation of fishing in sanctuary zones appears responsible for observed differences in the populations of these fish. These results demonstrate that recreational fishing pressure may be sufficient to deplete fish populations below that of adjacent protected areas and that the effect of recreational fishing in coral reef habitats may be greater than previously thought.     

Effects of reef-top gathering and fishing on invertebrate abundance across take and no-take zones

Gathering of molluscs on the reef-top, largely by women, is part of the traditional fishery practised by Bedouin in South Sinai, Egypt. The catch is dominated by Tridacna spp. and Octopus spp. Within the Nabq Managed Resource Protected Area, on the southern Gulf of Aqaba coast, a network of no-take zones (NTZs) was established (in 1995) to promote sustainable management of finfish stocks. Since this zoning also applied to exploitation of invertebrates, surveys of large species of molluscs and echinoderms across selected NTZs and adjacent fished areas were conducted (over 2000-2002) to assess any effects of gathering. Pooled data from all three years showed significantly higher abundances of Tridacna and Tectus dentatus in the NTZs, with greater abundances occurring at the reef edge zone. Size-frequency distributions revealed both a greater size range of Tridacna and a greater mean size of both Tridacna and Te. dentatus, within the NTZs, as compared to the fished areas. The size-frequency distribution of gleaned Tridacna, determined from discarded shells, also showed a smaller size range than did live Tridacna within the NTZs. By contrast, holothurians, which are not currently exploited by the local Bedouin, showed greater abundance in fished areas than in NTZs. Large diadematid sea urchins, along with the non-commercial strombs, Strombus gibberulus and Strombus fasciatus, were also significantly more abundant within fished areas, an effect presumed due to reduced predation pressure from fish as a result of fishing. Within the fished areas, there was a positive relationship between local abundance of Tridacna and of diadematids, thought to be due to high densities of the urchins acting as a deterrent against gathering. The establishment of NTZs has led to significant differences in invertebrate populations between take zones (TZ) and no-take zones. However, since there can be little or no spillover of adults of less mobile or sedentary invertebrates from NTZs to fished areas, any benefit to the fishery will depend largely on the greater larval production and export from protected populations.     

Long-term changes in deep-water fish populations in the northeast Atlantic: a deeper reaching effect of fisheries?

A severe scarcity of life history and population data for deep-water fishes is a major impediment to successful fisheries management. Long-term data for non-target species and those living deeper than the fishing grounds are particularly rare. We analysed a unique dataset of scientific trawls made from 1977 to 1989 and from 1997 to 2002, at depths from 800 to 4800 m. Over this time, overall fish abundance fell significantly at all depths from 800 to 2500 m, considerably deeper than the maximum depth of commercial fishing (approx. 1600 m). Changes in abundance were significantly larger in species whose ranges fell at least partly within fished depths and did not appear to be consistent with any natural factors such as changes in fluxes from the surface or the abundance of potential prey. If the observed decreases in abundance are due to fishing, then its effects now extend into the lower bathyal zone, resulting in declines in areas that have been previously thought to be unaffected. A possible mechanism is impacts on the shallow parts of the ranges of fish species, resulting in declines in abundance in the lower parts of their ranges. This unexpected phenomenon has important consequences for fisheries and marine reserve management, as this would indicate that the impacts of fisheries can be transmitted into deep offshore areas that are neither routinely monitored nor considered as part of the managed fishery areas.     

Batch fecundity of Lutjanus carponotatus (Lutjanidae) and implications of no-take marine reserves on the Great Barrier Reef, Australia

This study investigated body size to fecundity relationships of a reef fish species targeted by line fishing, and examines the potential benefits of increased batch fecundity in no-take reserves compared to fished areas around the Palm, Whitsunday and Keppel Island Groups, Great Barrier Reef, Australia. Lutjanus carponotatus batch fecundity increased with fork length in a non-linear relationship that was best described by a power function. Batch fecundity differed by more than 100-fold among individuals, with a range from 7,074 to 748,957 eggs in fish ranging from 184 to 305 mm fork length. Furthermore, egg diameter increased with fish size. Based on underwater visual census, the potential batch fecundity per unit area in all three island groups ranged from 1.0 to 4.2 times greater in the no-take reserves than in the fished areas between 2001 and 2004. In 2002, a mean 2.3-fold difference in biomass between no-take reserves and fished areas converted to a mean 2.5-fold difference in batch fecundity per unit area. Greater batch fecundity, longer spawning seasons and potentially greater larval survival due to larger egg size from bigger individuals might significantly enhance the potential benefits of no-take marine reserves on the Great Barrier Reef.     

Changes in invertebrate and macroalgal populations in Tasmanian marine reserves in the decade following protection

Densities of macrobenthic invertebrates and macro-algae in four Tasmanian ‘no-take’ marine protected areas (MPAs) were monitored annually for 10 years following MPA establishment, with changes compared to those at external (fished) reference locations. Fishing substantially influenced the population characteristics of many species, including altering the mean size and abundance of rock lobsters and the abundance of prey species such as urchins and abalone. Strong declines in abundances of purple urchins and abalone within the largest MPA at Maria Island indicate likely indirect effects related to protection of predators from fishing. The two smallest MPAs (ca. 1 km coastal span) generated few detectable changes. Our results affirm the importance of long-term monitoring and the value of MPAs, when sufficiently large, as reference areas for determining and understanding ecosystem effects of fishing in the absence of historical baseline data.     

Parrotfish Size: A Simple yet Useful Alternative Indicator of Fishing Effects on Caribbean Reefs?

There is great need to identify simple yet reliable indicators of fishing effects within the multi-species, multi-gear, data-poor fisheries of the Caribbean. Here, we investigate links between fishing pressure and three simple fish metrics, i.e. average fish weight (an estimate of average individual fish size), fish density and fish biomass, derived from (1) the parrotfish family, a ubiquitous herbivore family across the Caribbean, and (2) three fish groups of “commercial” carnivores including snappers and groupers, which are widely-used as indicators of fishing effects. We hypothesize that, because most Caribbean reefs are being heavily fished, fish metrics derived from the less vulnerable parrotfish group would exhibit stronger relationships with fishing pressure on today’s Caribbean reefs than those derived from the highly vulnerable commercial fish groups. We used data from 348 Atlantic and Gulf Rapid Reef Assessment (AGRRA) reef-surveys across the Caribbean to assess relationships between two independent indices of fishing pressure (one derived from human population density data, the other from open to fishing versus protected status) and the three fish metrics derived from the four aforementioned fish groups. We found that, although two fish metrics, average parrotfish weight and combined biomass of selected commercial species, were consistently negatively linked to the indices of fishing pressure across the Caribbean, the parrotfish metric consistently outranked the latter in the strength of the relationship, thus supporting our hypothesis. Overall, our study highlights that (assemblage-level) average parrotfish size might be a useful alternative indicator of fishing effects over the typical conditions of most Caribbean shallow reefs: moderate-to-heavy levels of fishing and low abundance of highly valued commercial species.     

Spatial and temporal variation of abundance,biomass and diversity within marine reserves in the Philippines

Aim The objective of this study was to investigate the influence of protection duration (years of fishing closure) and location (distance from shore) on reef fish diversity. Location Danajon Double Barrier Reef, Bohol, Philippines. Methods Reef fish abundance and size structure, by species, were obtained monthly using replicated underwater visual belt transects (n = 8; 70 × 5‐m belt transects) over 3 years (2002–2005) at eight sites that included six marine reserves and two unprotected reef areas. We analysed species accumulation curves, diversity indices and abundance–biomass comparison (ABC) curves within and across the study sites to assess the influence of protection duration and location. Results Analyses showed that longer protection duration impacted reef fish diversity at both inshore and offshore sites by shifting ABC curves from higher abundance than biomass curves at fished sites to higher biomass than abundance curves at most of the protected sites. Protection duration did not significantly influence either the rate of species accumulation within sites or the 12 diversity indices measured across the study sites. The offshore sites consistently showed higher rates of species accumulation and diversity indices values than inshore sites with similar protection duration. One protected offshore young marine reserve site that has been assessed as the least well‐managed showed patterns more consistent with the fished sites. Main conclusions Analyses showed that protection duration mainly impacted diversity by increasing the dominance of large‐bodied species and enhancing total biomass. Besides protection duration, reserve location influenced species accumulation curves and diversity indices.     

Strong direct and inconsistent indirect effects of fishing found using stereo-video: Testing indicators from fisheries closures

Candidate indicators of the direct and indirect effects of fishing can be developed by investigating fisheries closures. We tested a suite of such indicators in areas open to fishing but with suspected differences in effort, using baited remote underwater stereo-video methods. In particular, we predicted that greater fishing would result in decreased biomass of high risk target species and indirectly increase the biomass of small-bodied non-target species. As predicted, the biomass of target species was found to be greater in areas of lower fishing effort and in deeper waters. However, no indirect effects of fishing were detected and any community-level effects were driven by differences in the biomass of target species. In particular, assemblage length class analysis of covariance (ANCOVA), size spectra analysis and the abundance-biomass comparison (ABC) method did not provide any evidence of indirect effects of fishing. The magnitude of the differences in fishing effort between the two areas sampled, may be sufficient to significantly affect target fisheries species, but insufficient to lead to indirect effects on non-target populations. It is also possible that the predicted indirect effects do not occur in this assemblage, due to weak trophic linkages between species. Differences observed using the ABC method were attributed to variation in the abundance of large herbivorous fishes, which are not fished. We also found assemblage length class ANCOVA and size spectra to be insensitive to the direct effects of fishing where large numbers of non-target individuals are sampled along with fished species. We suggest diet studies and comparisons across stronger gradients in fishing pressure to further investigate the indirect effects of fishing in this assemblage.     

Similarities between Line Fishing and Baited Stereo-Video Estimations of Length-Frequency: Novel Application of Kernel Density Estimates

Age structure data is essential for single species stock assessments but length-frequency data can provide complementary information. In south-western Australia, the majority of these data for exploited species are derived from line caught fish. However, baited remote underwater stereo-video systems (stereo-BRUVS) surveys have also been found to provide accurate length measurements. Given that line fishing tends to be biased towards larger fish, we predicted that, stereo-BRUVS would yield length-frequency data with a smaller mean length and skewed towards smaller fish than that collected by fisheries-independent line fishing. To assess the biases and selectivity of stereo-BRUVS and line fishing we compared the length-frequencies obtained for three commonly fished species, using a novel application of the Kernel Density Estimate (KDE) method and the established Kolmogorov–Smirnov (KS) test. The shape of the length-frequency distribution obtained for the labrid Choerodon rubescens by stereo-BRUVS and line fishing did not differ significantly, but, as predicted, the mean length estimated from stereo-BRUVS was 17% smaller. Contrary to our predictions, the mean length and shape of the length-frequency distribution for the epinephelid Epinephelides armatus did not differ significantly between line fishing and stereo-BRUVS. For the sparid Pagrus auratus, the length frequency distribution derived from the stereo-BRUVS method was bi-modal, while that from line fishing was uni-modal. However, the location of the first modal length class for P. auratus observed by each sampling method was similar. No differences were found between the results of the KS and KDE tests, however, KDE provided a data-driven method for approximating length-frequency data to a probability function and a useful way of describing and testing any differences between length-frequency samples. This study found the overall size selectivity of line fishing and stereo-BRUVS were unexpectedly similar.     

Consistent Selection towards Low Activity Phenotypes When Catchability Depends on Encounters among Human Predators and Fish

Together with life-history and underlying physiology, the behavioural variability among fish is one of the three main trait axes that determines the vulnerability to fishing. However, there are only a few studies that have systematically investigated the strength and direction of selection acting on behavioural traits. Using in situ fish behaviour revealed by telemetry techniques as input, we developed an individual-based model (IBM) that simulated the Lagrangian trajectory of prey (fish) moving within a confined home range (HR). Fishers exhibiting various prototypical fishing styles targeted these fish in the model. We initially hypothesised that more active and more explorative individuals would be systematically removed under all fished conditions, in turn creating negative selection differentials on low activity phenotypes and maybe on small HR. Our results partly supported these general predictions. Standardised selection differentials were, on average, more negative on HR than on activity. However, in many simulation runs, positive selection pressures on HR were also identified, which resulted from the stochastic properties of the fishes’ movement and its interaction with the human predator. In contrast, there was a consistent negative selection on activity under all types of fishing styles. Therefore, in situations where catchability depends on spatial encounters between human predators and fish, we would predict a consistent selection towards low activity phenotypes and have less faith in the direction of the selection on HR size. Our study is the first theoretical investigation on the direction of fishery-induced selection of behaviour using passive fishing gears. The few empirical studies where catchability of fish was measured in relation to passive fishing techniques, such as gill-nets, traps or recreational fishing, support our predictions that fish in highly exploited situations are, on average, characterised by low swimming activity, stemming, in part, from negative selection on swimming activity.     

Length-dependent changes in egg size and fecundity in females, and brooded embryo size in males, of fork-tailed catfishes (Pisces: Ariidae) from the Sepik River, Papua New Guinea, with some implications for stock assessments

Data suggest that mature egg weight is positively correlated to female parent length in all five species of fork-tailed catfish studied. Embryo weight is positively correlated with the length of the male mouthbrooding parent in the four species where data are available. Non-random mate pairing is probably between fish of equivalent size. Fecundity appears to be linearly related to female fish length in all species. There is no significant correlation between fecundity and female weight, probably because egg size increases with fish size. Low fecundities and breeding behaviour suggest that recruitment is likely to be highly density-dependent and the stocks vulnerable to increased mortality (fishing). Changes in egg size with fish size may account for deviations from a cube relationship between fecundity and fish length in other species. The relevance of this to other fish stock assessments is discussed. Attention is drawn to possible changes in egg size with fish length which could affect recruitment in fished stocks, depending on the specific relationship and the length at which mature fish are caught.     

Natural fishing experiments in marine reserves 1983 – 1993: roles of life history and fishing intensity in family responses

 This study examined the effect of fishing on the abundance and species richness of families of coral reef fish at two islands (Sumilon and Apo) in the Philippines from 1983 to 1993. Natural fishing experiments occurred in marine reserves at each island, where long term estimates of fishing intensity were available. Responses to fishing were interpreted in terms of life histories of fish. The intensity of fishing and fish life histories were generally good predictors of the differential rates of decline and recovery of abundance in response to fishing. Large predators had vulnerable life histories (low rates of natural mortality, growth and recruitment) and were subjected to high intensity fishing. They declined significantly in density when fished and increased significantly but slowly when protected from fishing. Caesionidae, a family with a life history resilient to fishing (high rates of natural mortality, growth and recruitment) but fished intensively also declined rapidly in abundance when fished. Thus, knowledge of life history alone was insufficient to predict response to fishing. Acanthuridae were fished relatively hard and had a life history of intermediate vulnerability but displayed weak responses to fishing. Thus level of fishing intensity alone was also not sufficient to predict response to fishing. For Chaetodontidae, effects of fishing conformed to expectations based on life history and fishing intensity at one island but not the other. Three families with intermediate vulnerability and subjected to intermediate to light fishing (F. Scaridae, Labridae and Mullidae) displayed predictably weak responses to fishing, or counter-intuitive responses (e.g., increasing in abundance following fishing). These counter-intuitive responses were unlikely to be secondary effects of increase in prey in response to declines of predators. Two lightly-fished families with resilient life histories (F. Pomacentridae, Sub F. Anthiinae) predictably displayed weak numerical responses to fishing except during a period of use of explosives and drive nets. Accepted: 30 June 1998     

Structural change in an exploited fish community: a consequence of differential fishing effects on species with contrasting life histories

1. An understanding of the links between life histories and responses to exploitation could provide the basis for predicting shifts in community structure by identifying susceptible species and linking life-history tactics with population dynamics.
2. We examined long-term trends in the abundance of species in the North Sea bottom-dwelling (demersal) fish community. Between 1925 & 1996 changes in species composition led to an increase in mean growth rate, while mean maximum size, age at maturity and size at maturity decreased. The demersal fish community was increasingly heavily fished during this period.
3. Trends in mean life-history characteristics of the community were linked to trends in abundance of component species. An approach based on phylogenetic comparisons was used to examine the differential effects of fishing on individual species with contrasting life histories.
4. Those species that decreased in abundance relative to their nearest relative, matured later at a greater size, grew more slowly towards a greater maximum size and had lower rates of potential population increase. The phylogenetically based analyses demonstrated that trends in community structure could be predicted from the differential responses of related species to fishing.
5. This is the first study to link exploitation responses of an entire community to the life histories of individual species. The results demonstrate that fishing has greater effects on slower growing, larger species with later maturity and lower rates of potential population increase. The comparative approach provides a basis for predicting structural change in other exploited communities.     

Responses of benthic scavengers to fishing disturbance by towed gears in different habitats

The aggregation and feeding behaviour of invertebrate scavengers in areas disturbed by trawling was investigated at three different localities. At each site a fishing disturbance was created using a commercial 4 m beam trawl and scavenger density was quantified using a light beam trawl. At one site two diver surveys were also carried out; along a line fished with a scallop dredge or a beam trawl on two separate occasions. For all experiments the fished and adjacent unfished control areas were sampled before, and at intervals after, the initial fishing disturbance. Sampling with the light beam trawl revealed that hermit crabs Pagurus bernhardus moved into areas which had been fished with a 4 m beam trawl at an experimental site near Anglesey. The density of these hermit crabs increased significantly in the fished area after fishing had taken place, but no change in density occurred in the adjacent control (unfished) area. At two other sites (Red Wharf Bay, Anglesey and a site offshore from Walney Island) there were no detectable increases in scavenger numbers in the fished areas. Furthermore, at the site near Walney Island, numbers of hermit crabs P. bernhardus, swimming crabs Liocarcinus depurator and starfish Asterias rubens actually decreased after fishing. Thus the responses of scavengers to towed fishing gears varied considerably between different communities. At Red Wharf Bay, divers observed similar responses of scavengers to both beam trawl and scallop dredge disturbance. Four predatory species were observed feeding in the fished area; starfish A. rubens, hermit crabs P. bernhardus, brittlestars Ophiura ophiura and whelks Buccinum undatum. These predators fed on damaged bivalves, echinoderms, crustaceans, whelks and polychaetes. The proportion of starfish feeding in the fished area was significantly higher after fishing had taken place. Demersal fishing activities provide food for scavengers in the form of damaged animals which are left in the tracks of the trawl or dredge. The responses of scavengers to fishing disturbance are not always manifested as a large increase in their abundance. It is clear that the magnitude of response varies between species and between habitat types.     

Length-weight relationship of 74 fish species caught in the continental coast of Ecuador

This work analysis the length-weight relationships for fish species captured by artisanal fishery along the continental coast of Ecuador. Fishermen used the following fishing gear: beach seine nets (5.1–31.8 mm), shrimp trawl nets (21.8–31.8 mm) and bottom gill nets (54.1–203.2 mm). Sampling took place during the years 2012 and 2014. Frequency of sampling was monthly, and it was completed systematically from Southern toward Northern Provinces. Length-weight relationship (LWR) was realized by the power model (y = a × x^b), for species with a bivariate dataset >70. A total of 59 commercial and 15 non-commercial species were registered. For 74 species, our analysis including a higher total length not reported in LWR estimates previously. The determination coefficient (r²) value was always above 0.95.     

A preliminary market-based analysis of the Pohnpei,Micronesia, grouper (Serranidae: Epinephelinae) fishery reveals unsustainable fishing practices

Serranids are important components of artisanal and commercial catch worldwide, but are highly susceptible to overfishing. In Pohnpei (Micronesia), a recent coral reef fish market survey revealed a reliance on night-time spearfishing and a serranid catch composed primarily of juveniles and small adults of practically all epinepheline species. Fishing effort was concentrated in one of five municipalities and was disproportionate to the population distribution. Lagoon areas were fished preferentially to outer reef areas, with both catch size distribution and species composition similar between the two areas. Some species were unique to a particular gear type, but catch composition did not vary substantially between spear and line fishing. Existing seasonal sales bans, meant to protect reproductively active serranids, appeared to place additional pressure on other families during ban periods. The study identified the need for a comprehensive management plan that merges traditional measures, including size limits and gear restrictions, with precautionary management tools. Specifically, the scale and scope of marine protected areas should be increased to protect juveniles and other life history stages over wider areas than currently employed.     

Experimental gill-netting of reef fish: Species-specific responses modify capture probability across mesh sizes

Gill-nets are highly selective in terms of the sizes of fish they catch, but often unselective in terms of the suite of fish species they capture. We investigated gill-net selectivity from the point of view of behavioural interactions between the fish and the gear. We observed interactions between fish and gill-nets of three mesh sizes (65 mm, 88 mm & 110 mm) set over rocky reefs in southern New Zealand. There were significant differences among eight species of mobile reef fish in their response to gill-nets and in their capture rates. Some species were more vulnerable because of their use of habitat, swimming motion or morphology. Species that occupied low visibility habitats (e.g., the herbivorous Odax pullus, which mostly swims beneath the algal canopy) were more susceptible to being caught because they had little time to detect and avoid the gill-nets. Species with carangiform or sub-carangiform swimming motion (e.g., Latridopsis ciliaris or O. pullus) were more susceptible to being caught because once in the gill-net, they could only attempt to force their way forwards becoming wedged further into the mesh. Species whose morphology makes tangling in the mesh more likely (e.g., large or protruding spines (Aplodactylus arctidens), fins (L. ciliaris) or opercula) are also more susceptible to being caught. Some species, particularly the common labrid Notolabrus celidotus, were less susceptible than other species to being caught. Fewer than 1% of 538 N. celidotus observed within one metre of the gill-nets were caught. Most N. celidotus altered their swimming direction near the gill-nets and did not hit the mesh. N. celidotus that swam through the nets were smaller than those that swam over the gill-nets or turned away. The fact that different size classes had different responses suggests that interactions with the gill-net are actively controlled. To divers, it appeared that this species could readily detect the gill-nets and treated them as part of the seascape. Furthermore, their labriform swimming motion allowed them to swim backwards out of gill-nets to avoid becoming caught. The species-specific responses of reef fish near the gill-nets and behavioural differences may explain the low numbers of some common reef fish that are caught in gill-nets and the disproportionately high numbers of others. The potentially great ancillary effects from by-catch of important species of untargeted reef fish, birds and marine mammals make gill-nets a somewhat blunderbuss method of catching fish on coastal reefs.