title: Alternative reproductive tactics and inverse size-assortment in a high-density fish spawning aggregation.
abstract: At high densities, terrestrial and marine species often employ alternate reproductive tactics (ARTs) to maximize reproductive benefits. We describe ARTs in a high-density and unfished spawning aggregation of the squaretail grouper (Plectropomus areolatus) in Lakshadweep, India.
  
  
  
  As previously reported for this species, territorial males engage in pair-courtship, which is associated with a pair-spawning tactic. Here, we document a previously unreported school-courtship tactic; where territorial males court multiple females in mid-water schools, which appears to culminate in a unique 'school-spawning' tactic. Courtship tactics were conditional on body size, local mate density and habitat, likely associated with changing trade-offs between potential mating opportunities and intra-sexual competition. Counter-intuitively, the aggregation showed a habitat-specific inverse size-assortment: large males courted small females on the reef slope while small males courted equal-sized or larger females on the shelf. These patterns remained stable across two years of observation at high, unfished densities.
  
  
  
  These unique density-dependent behaviours may disappear from this aggregation as overall densities decline due to increasing commercial fishing pressure, with potentially large consequences for demographics and fitness.
authors.affiliation: Oceans and Coasts Program, Nature Conservation Foundation, 3076/5, 4th Cross, Gokulam Park, Mysore, Karnataka, 570002, India. rucha@ncf-india.org.|Manipal University, Manipal, Karnataka, 576104, India. rucha@ncf-india.org.
authors.forename: Rucha
authors.initials: R
authors.lastname: Karkarey
authors.affiliation: Post-graduate Programme in Wildlife Biology and Conservation, National Centre for Biological Sciences-Wildlife Conservation Society, Bangalore, Karnataka, India.
authors.forename: Amod
authors.initials: A
authors.lastname: Zambre
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore, Karnataka, India.
authors.forename: Kavita
authors.initials: K
authors.lastname: Isvaran
authors.affiliation: Oceans and Coasts Program, Nature Conservation Foundation, 3076/5, 4th Cross, Gokulam Park, Mysore, Karnataka, 570002, India.|Centre d'Estudis Avançats de Blanes (CSIC), Blanes, Spain.
authors.forename: Rohan
authors.initials: R
authors.lastname: Arthur
mesh_terms: D000818:Animals; D003380:Courtship; D005260:Female; D005399:Fishes / Q000502:physiology*; D008297:Male; D012098:Reproduction; D012726:Sexual Behavior, Animal
keywords: Alternative reproductive tactics; High mating density; Inverse size-assortment; Shoal and pair courtship tactics; Spawning aggregation; Squaretail grouper