Factors affecting the local abundance of two anemonefishes (Amphiprion frenatus and A. perideraion) around a semi-closed bay in Puerto Galera, the Philippines

Nakamura

et al. 2022

Preprint

Self Cite

Many marine species have a pelagic larval phase that undergo dispersal among habitats. Studies on marine larval dispersal have revealed a large variation in the spatial scale of dispersal, and accumulated evidence has shown that seascape patchiness is the major determinant for variation in self-recruitment. However, few studies have investigated the influence of geographic settings on marine larval dispersal. Bays or lagoons generally enhance the retention of larvae, while larvae are more likely to be flushed by strong currents in open coasts. To examine associations between larval dispersal, geographic setting, and hydrodynamics, we compared fin-scale dispersal patterns, self-recruitment, and local retention of two anemonefishes (Amphiprion frenatus and A. perideraion) between a semi-enclosed bay and an open coast in the Philippines combining genetic parentage analysis and biophysical dispersal modelling. Contrary to our expectations, parentage analysis revealed lower estimates of self-recruitment in the semi-closed bay (0‒2%) than in the open coast (14‒15%). The result was consistent with dispersal simulations predicting lower local retention and self-recruitment in the former (0.4% and 19%) than in the latter (2.9% and 38%). Dispersal modelling also showed that cross-shore currents toward offshore were much stronger around the semi-closed bay and were negatively correlated with local retention and self-recruitment. These results suggest that stronger cross-shore currents around the semi-closed bay transport anemonefish larvae to the offshore and mainly contributed to the lower self-recruitment. Our results highlight difficulty in predicting self-recruitment from geographic setting alone and importance of hydrodynamics on it.

Section: Discussionmentioning

confidence: 73%

Section: Study Species and Study Sitesmentioning

confidence: 99%

Section: Study Species and Study Sitesmentioning

confidence: 99%

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Hydrodynamics shapes self-recruitment in anemonefishes

Nakamura

et al. 2022

Preprint

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“…In November 2012, we conducted a preliminary survey by snorkeling on coral reefs inside and outside the MPA to record the location of anemonefish and host anemones, because they were abundant only in such habitats (Figure ; Sato, Honda, et al., ). A GPS device (Garmin eTrex 30) was used to determine the locations.…”

Section: Methodsmentioning

confidence: 99%

“…On the basis of the location data, we investigated the distribution patterns of anemonefish on coral reefs at a depth of 0.5–15 m using SCUBA, from May to July in 2013 (Figure ). We counted the abundance of the target species at each anemone, recorded their total length (TL, mm), and measured long and short axial lengths (cm) of host sea anemones, using a ruler to estimate the habitat area as an oval by (long axial length) × (short axial length) × π/4 (Hattori, ; Sato, Honda, et al., ). Based on the measured fish size, we separately recorded adult (>30 mm TL) and juvenile (≤30 mm TL) abundance levels of target species in accordance with the classification of juveniles for the parentage analysis below.…”

Section: Methodsmentioning

confidence: 99%

Marine protected area restricts demographic connectivity: Dissimilarity in a marine environment can function as a biological barrier

et al. 2017

Ecology and Evolution

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The establishment of marine protected areas (MPAs) can often lead to environmental differences between MPAs and fishing zones. To determine the effects on marine dispersal of environmental dissimilarity between an MPA and fishing zone, we examined the abundance and recruitment patterns of two anemonefishes (Amphiprion frenatus and A. perideraion) that inhabit sea anemones in different management zones (i.e., an MPA and two fishing zones) by performing a field survey and a genetic parentage analysis. We found lower levels of abundance per anemone in the MPA compared to the fishing zones for both species (n = 1,525 anemones, p = .032). The parentage analysis also showed that lower numbers of fishes were recruited from the fishing zones and outside of the study area into each anemone in the MPA than into each anemone in the fishing zones (n = 1,525 anemones, p < .017). However, the number of self‐recruit production per female did not differ between the MPA and fishing zones (n = 384 females, p = .516). Because the ocean currents around the study site were unlikely to cause a lower settlement intensity of larvae in the MPA, the ocean circulation was not considered crucial to the observed abundance and recruitment patterns. Instead, stronger top‐down control and/or a lower density of host anemones in the MPA were potential factors for such patterns. Our results highlight the importance of dissimilarity in a marine environment as a factor that affects connectivity.

Hydrodynamics rather than type of coastline shapes self‐recruitment in anemonefishes

Limnology & Oceanography

Nakamura

et al. 2023

Many marine species have a pelagic larval phase that undergo dispersal among habitats. Studies on marine larval dispersal have revealed a large variation in the spatial scale of dispersal and self‐recruitment. However, few studies have investigated the influence of types of coastline (e.g., bay vs. open coast) on marine larval dispersal. Bays or lagoons generally enhance the retention of larvae, while larvae are more likely to be flushed by strong currents in open coasts. To examine associations between larval dispersal, coastline type, and hydrodynamics, we compared fin‐scale dispersal patterns, self‐recruitment, and local retention (LR) of two anemonefishes (Amphiprion frenatus and Amphiprion perideraion) between a semi‐enclosed bay and an open coast in the Philippines combining genetic parentage analysis and biophysical dispersal modeling. Contrary to our expectations, parentage analysis revealed lower estimates of self‐recruitment in the semi‐closed bay (0%) than in the open coast (14–15%). The result was consistent with dispersal simulations predicting lower LR and self‐recruitment in the semi‐closed bay (0.4% and 19%) compared to the open coast (2.9% and 38%). Dispersal modeling also showed that cross‐shore currents toward offshore were much stronger around the semi‐closed bay and were negatively correlated with LR and self‐recruitment. These results suggest that stronger cross‐shore currents around the semi‐closed bay transport anemonefish larvae to the offshore and mainly contributed to the lower self‐recruitment. Our results highlight importance of hydrodynamics on larval dispersal and difficulty in predicting self‐recruitment from coastline type alone.