Larval Dispersal Modeling Reveals Low Connectivity among National Marine Protected Areas in the Yellow and East China Seas

Abstract

Marine protected areas (MPAs) are vital for protecting biodiversity, maintaining ecosystem integrity, and tackling future climate change. The effectiveness of MPA networks relies on connectivity, yet connectivity assessments are often skipped in the planning process. Here we employed a multi-species biophysical model to examine the connectivity patterns formed among the 21 national MPAs in the Yellow and East China Seas. We simulated the potential larval dispersal of 14 oviparous species of five classes. Larvae of non-migratory species with pelagic larval duration (PLD) were assumed to be passive floating particles with no explicit vertical migration. A total of 217,000 particles were released according to spawning period, living depth, and species distribution, and they were assumed to move with currents during the PLD. Most larvae were dispersed around the MPAs (0–60 m isobaths) and consistent with the currents. Larval export increased with PLD and current velocity, but if PLD was too long, few larvae survived due to high daily mortality during pelagic dispersal. The overall connectivity pattern exhibited a north-to-south dispersal trend corresponding to coastal currents. Our results indicated that the national MPAs in the Yellow and East China Seas did not form a well-connected network and nearly 30% of them were isolated. These MPAs formed three distinct groups, one in the Yellow Sea ecoregion and two in the East China Sea ecoregion. Four MPAs (all in coastal Zhejiang) emerged as key nodes for ensuring multi-generational connectivity. Under the pressure of future climate change, high self-recruitment and low connectivity present significant challenges for building well-connected MPA networks. We suggest adding new protected areas as stepping stones for bioecological corridors. Focused protection of the Yellow Sea ecoregion could have a good effect on the southern part of the population recruitment downstream. Conservation management should be adjusted according to the life cycles and distributions of vulnerable species, as well as seasonal changes in coastal currents. This study provides a scientific basis for improving ecological connectivity and conservation effectiveness of MPAs in the Yellow and East China Seas.

A Larval “Recruitment Kernel” to Predict Hatching Locations and Quantify Recruitment Patterns

“…We estimated the correlation between PLD and both the travel and linear distances. A longer PLD allows larvae to travel larger distances (Lu et al., 2023; Selkoe & Toonen, 2011; Shanks, 2009). We found a strong linear correlation between PLD and travel distance and a moderate correlation between PLD and linear distance, calling into question the pervasive use of PLD as a proxy for dispersal potential.…”

“…The larvae were assumed to be passive particles over their PLD (pelagic larval duration), we thus refer to larval age as PLD to be consistent with the broader literature (D’Aloia et al., 2015). The PLD is defined as the number of days an individual spends in the water column moving from the hatching site to the settlement or nursery location during its larval phase (Lu et al., 2023; Selkoe & Toonen, 2011; Shanks, 2009). The pelagic larval period for Lake Whitefish in the western basin of Lake Erie is typically from April 15 to May 15 (Amidon et al., 2021a), which overlaps with our larval sampling in 2018–2019.…”

“…Genetic‐based approaches, that assign offspring to parents based on the similarity of their gene analysis, do not account for larval mortality and only measure successful dispersal and recruitment (D’Aloia et al., 2015; Almany et al., 2017). Forward‐in‐time Lagrangian particle tracking models have been widely applied to track larval trajectories, estimate dispersal distances and study larval dispersal (Chaput et al., 2022; Lu et al., 2023; Uchiyama et al., 2018). Forward Lagrangian models are well suited to study dispersal between potential spawning areas and potential settlement areas, however, they do not often consider multiple environmental and biological factors that are necessary to understand the survival and selection of larvae during dispersal.…”

Genetic Diversity and Connectivity of Ocypode ceratophthalmus in the East and South China Seas and Its Implications for Conservation

“…Many protected species such as Acropora solitarvensis, Epinephelus akaara and Epinephelus bruneus spawn during summer [ 52 ]. The summer fishing moratorium implemented by the Chinese government in the East and South China Seas [ 53 , 54 ] contributes to the protection of larvae and may complement the MPA network [ 55 ].…”

“…However, focusing solely on the spawning patterns of these species for reserve design will decrease protection of fall–winter spawners when the direction of the gyres and the location of upstream larval sources reverses [ 51 ]. For example, at least some important species such as Anguilla japonica and Penaeus japonicus also spawn exclusively during fall–winter [ 52 ]. So, flexible management strategies could be carried out during the winter for the conservation of these species.…”