Caribbean Spiny Lobster

The recent status and trends in the Saba Bank fisheries up to and including 2015 port sampling data have been previously reported by de Graaf et al. (2017) and a policy brief has also been written based on those results (Debrot and de Graaf (2018). The purpose of this report is to update recent catch trends in the Saba Bank fisheries with the data from 2016 and 2017.

For the lobster fishery (Panulirus argus), the number of fishing trips (and number of traps set) gradually grew from 2012 to 2015 but has since leveled off. The resulting landings of lobster have shown a similar pattern of increase up to 2015 but have now leveled off at around 70 tons annually. Increasing landings per unit effort indicate that the formerly reduced lobster abundance, which had been declining since 2000 and which had reached its lowest level in 2011, has subsequently increased relatively steadily all through 2017, and now has increased back to levels close to those of 2007. The average size of lobsters taken, continues to be large, which is favourable to gradual stock recovery.

Mixed landings of reef fish in the lobster fishery have fluctuated between 10 and 20 tons annually. The LPUE abundance index in bycatch species also shows a decrease of about 35% from high levels in 2000 and 2007 to lowest levels in 2011, followed by an increase up to 2013, after which landings have levelled off.

In the redfish trap fishery (Lutjanus spp.), the number of trips in the redfish trap fisheries had grown significantly during the period 2012 to 2015. In 2016 effort increased again to 625 trips. In 2017 the exerted fishing effort dropped down to about 350 trips, a level seen last in 2012. The landings of redfish have fluctuated over this period, with lower values in 2012 and 2017 and higher values in 2014 and 2016. The LPUE abundance index shows a decrease by 50% between 2007 and 2011, followed by an increase to slightly higher and constant values between 2012 and 2016, while in 2017 the LPUE abundance index continued increasing. The only snapper for which sufficient data was available, was the silk snapper, Lutjanus vivanus. Average size of the silk snappers landed continued its increasing trend, indicative of gradual stock recovery. The drop in snapper landings, despite the higher LPUE in 2017, can especially be ascribed to the 6-month closed season implemented that year (Graaf et al. 2017).

The overall conclusion is that for both the lobster and redfish stocks, stock status, based on the LPUE index and size-structure trends have continued in developing favorably. Bottom drop longline, pelagic and bycatch landings have remained much less important and have shown no significant new developments.

There are two matters of concern that require follow up. Firstly, the positive prognosis for the snapper “stock” status may partly be based on targeting geographically different stocks as well as different species. Hence the data as collected and analyzed may actually be presenting a too optimistic assessment. To evaluate whether this is actually the case will require more detailed analysis based on individual species, as well as more accurate geographical recording of catches than as currently practiced. The second matter of concern regards the fate of the traps that were in the water on the Bank when the hurricanes Irma and Maria struck the area in September 2017. If trap loss was large, this may lead to higher detrimental impacts of ghost fishing in the coming years.

Abstract:

The Caribbean spiny lobster (Panulirus argus) is a widespread crustacean species. It inhabits shallow water reefs and rocky substrates from Brazil to Florida. The lobster fishery is one of the most important fisheries in the Caribbean (in 2011 the total catch was 35,642 tons), generating more than 456 million US dollars annually. However, the annual landings of P. argus throughout the Caribbean have been in decline since 1995 (FAO, 2013). Over-exploitation is thought to be one of the major causes of this decline (CRFM, 2011).

One of the areas where the spiny lobster fishery is important, is on the Saba Bank, a 2,200 km2 submerged plateau, near Saba in the northern Caribbean Sea. Spiny lobsters are fished exclusively with traps by nine small (11m) vessels operating from Saba. To determine the current status of the P.argus stock and its fishery on the Saba Bank, basic fisheries data were collected in 2012 and compared with similar studies conducted in 1999 and 2007.

The number of lobster traps hauled per fishing trip increased from 59 to 80 between 1999 and 2012 while the number of lobsters landed per trip decreased from 83 to 52 per trip during the same period. A similar declined was observed in the standardized (75 trap hauls per trip) CPUE both in number and total weight of lobster landed. No obvious changes in fishing areas on the Saba Bank were observed during this period.

The total catch of lobster was estimated as 62 t, 92 t and 38 t in 1999, 2007 and 2012, respectively. The high catch in 2007 was attributed to the higher number of estimated fishing trips in 2007 (1000) compared to 1999 (650) and 2012 (600). The lower estimated annual catch in 2012 compared to 1999 is attributed to a decline in CPUE. These result suggest a decrease in abundance of spiny lobster on the Saba Bank between 1999 and 2012, similar to decline observed in the wider Caribbean.

Size-at-maturity (CL50%) for male P.argus was found to be 92.2 (± 2.53 SE) mm carapace length, slightly below the minimum legal size (95mm CL). The mean size of landed male (109 mm CL) and female lobster (105 mm CL) showed that predominantly large, mature lobster are landed. Berried female spiny lobsters were observed on the Saba Bank throughout the year with a peak from March to June.

In addition to lobster, mixed reef fish were also landed in the lobster trap fishery. A total of 57 fish species were identified in the catches. Roughly 15 kg of mixed reef fish was landed per lobster trip, resulting in an estimated 8-10 t of mixed reef fish landed in 2012. The species composition (in weight) of the landed mixed fish consisted mainly of grunts (Haemulon album, H. melanurum and H. plumierii 30%), small groupers (Epinephelus guttatus and Cephalopholis fulva 17%) and queen trigger fish (Balistes vetula 21%). Only the mean total length of landed E. guttatus decreased significantly between 1999 (33 cm TL) and 2012 (31 cm TL).

In addition to the landed mixed fish, an estimated 10 t of mixed fish was discarded in 2012. The species composition (in weight) of the discarded mixed fish consisted mainly of grunts (H. melanurum and H. plumierii 34%), boxfishes (Acanthostracion quadricornis and A. polugonia 19%) and nurse sharks (Ginglymostoma cirratum 9%). 

This month’s issue focuses on marine monitoring. The results of the 2013 lobster fisheries monitoring project on the Saba Bank are in and on Curaçao a sea turtle monitoring programme is developing in line with regional efforts. Monitoring with standardised protocols, using appropriate methods, guarantees the collection of comparable data and provides added value to our islands and the region as a whole.

Content:

• Sea Turtle Conservation On Curaçao
• Lobster Research On The Saba Bank
• Overview of Research and Monitoring Efforts
• Calendar of Upcoming Events, Meetings and Workshops