Novel life‐history data for threatened seahorses provide insight into fishery effects

Abstract

Life-history variables for three incidentally captured species of seahorse (Kellogg's seahorse Hippocampus kelloggi, the hedgehog seahorse Hippocampus spinosissimus and the three-spot seahorse Hippocampus trimaculatus) were established using specimens obtained from 33 fisheries landing sites in Peninsular Malaysia. When samples were pooled by species across the peninsula, sex ratios were not significantly different from unity, and height and mass relationships were significant for all species. For two of these species, height at physical maturity (HM ) was smaller than the height at which reproductive activity (HR ) commenced: H. spinosissimus (HM = 99·6 mm, HR = 123·2 mm) and H. trimaculatus (HM = 90·5 mm, HR = 121·8 mm). For H. kelloggi, HM could not be estimated as all individuals were physically mature, while HR = 167·4 mm. It appears that all three Hippocampus spp. were, on average, caught before reproducing; height at 50% capture (HC ) was ≥HM but ≤HR . The results from this study probe the effectiveness of assessment techniques for data-poor fisheries that rely heavily on estimates of length at maturity, especially if maturity is poorly defined. Findings also question the sustainability of H. trimaculatus catches in the south-west region of Peninsular Malaysia, where landed specimens had a notably smaller mean height (86·2 mm) and markedly skewed sex ratio (6% males) compared with samples from the south-east and north-west of the peninsula.

Catch and trade bans for seahorses can be negated by non‐selective fisheries

“…This study adds to the growing literature about the massive impacts that small scale fisheries can have on marine life, including seahorses (Aylesworth, Phoonsawat, & Vincent, 2018; Hawkins & Roberts, 2004; Lawson, Foster, Lim, Chong, & Vincent, 2015). When poorly managed, small‐scale fisheries may irreparably damage vulnerable marine species, fish stocks, and habitats (Alfaro‐Shigueto et al, 2010).…”

Seasonal and spatial variation in the reproductive biology of the dwarf seahorse Hippocampus zosterae

“…Even with the growing number of studies on the life history of Hippocampus spp. (Correia et al, 2015;Curtis et al, 2017;Foster & Vincent, 2004;Harasti et al, 2012;Lawson et al, 2015;Masonjones et al, 2010), there is still a void in the knowledge of seasonal trends in their life-history traits and a lack of detailed studies on their reproduction, recruitment rate, mortality and growth from natural populations.…”

An assessment of West African seahorses in fisheries catch and trade

“…This is challenging due to limited ecological and fisheries information, yet global seahorse extraction amounts to 15–20 million individuals annually (Foster et al , ) gravely affecting many populations (Vincent et al , ). Targeted seahorse fisheries are predominantly for aquaria (Evanson et al , ), yet by‐catch, particularly by bottom‐trawl fisheries, helps supply traditional Asian medicine markets (Lawson et al , ). Recognizing potential sustainability issues, CITES issued a recommendation to Senegal and Guinea in May 2014 requiring data on the West African seahorse Hippocampus algiricus Kaup 1856 (Vincent, ), prompting this study.…”

“…engaging in reproduction) rather than the size at physical maturity (i.e. physically able to reproduce) (Morgan & Vincent, 2013;Lawson et al, 2015). This assumed a logistic relationship between height (H) and reproductive activity (R) as: where is the slope of a logistic curve and H 50 is the height at 50% reproductive activity.…”