British Marine Life Study Society

   Sea Stickleback
Common Name(s):
   Sea Stickleback
   15-spined Stickleback
Scientific Name:
                              Spinachia spinachia 
Family: Gasterosteidae 
Usual Size:  15 cm   to 20 cm 
  to 7 g
                                  Photograph by  Andy Horton

Similar species: 
Breeding:  Spring. The male builds a nest and guards it. See below.
Habitat: Shallow seas, estuaries, brackish to only 5 metres depth.Occasionally in tide pools. 
Food: Small crustaceans, live food only. In aquaria this fish will nip the fins of other fish and this behaviour has been observed in the wild, but it is not common. 
Range: All British coasts but not much further afield. Norway - Biscay, Baltic.

Additional Notes: 
    (by the late Chris Batt of "Silent World" Aquarium, Tenby, SW Wales).

 The only truly marine stickleback, this small fish, which normally reaches a maximum length of 150 mm, is probably the most attractive of the stickleback family. In breeding condition the male has a brown chequered pattern consisting of brown vertical bars alternating with silvery-yellow ones along the lateral line with a silvery-yellow underside whilst the female is much brassier yellow all over, with fewer vertical bars and is somewhat heavier in build. If gravid the female is easily recognisable by her sheer bulk. Both sexes may (or may not) have dorsal and ventral fin patterning. Freshly captured fish will normally only take only live food (small shrimp, Mysid, freshwater insect larvae, Daphnia, Gammarus), indeed, they may refuse food altogether. However, once settled, ours took frozen Mysid readily. These fish need a tank with plenty of cover - rocks or seaweeds or even (ugh!) plastic plants. They do not tolerate high nitrates and need high water quality generally, although we have kept them in water temperatures of up to 20° C.

 We had a male all winter, in our "Gelliswick Bay" tank, which had started nest-building on 15th March. The completed nest was about 100 mm from the bottom, amongst a clump of Chondrus crispus seaweed and really consisted of nothing but  bundled-up seaweed fronds, which were securely tied up with silk-like threads produced by the male's kidneys. We needed a female!

 Netting through kelp during an extreme low spring tide in Gelliswick Bay, Milford Haven on 21st March, Jim Hall and I caught about thirty of these fish (mostly males)- indeed they were the most frequently found fish, with Corkwing Wrasse, Crenilabrus melops, coming a close second. We selected about ten to take home and released the rest. I really only needed a couple of females but I thought that territorial behaviour might be interesting so I thought an extra male would also be useful. At this stage we were unsure of how to sex the fish but I picked out four of the plumpest ones and installed them in our tank, along with another male. To allow the fish to settle down, the lights were turned off and the tank was left alone.


 Next morning, we found that all of the new fish were being harrassed by the resident male and were, when not being chased, hiding in a vertical position (in both head- and tail-down positions!) in the corners of the tank and behind rocks, pretending to be bits of seaweed. No sign of eggs could be seen in the nest (although there may have been some in it). This behaviour continued for some days (one fish jumped out through a 2 cm gap in the glass cover). The "new" fish all sustained damage to the narrow caudal area and the tail-fin. There was no attempt at nest-building by the other male. 

 I subsequently removed three of the new fish, including the male, and installed them in our "touch-tank" which is larger, has plenty of cover and has a shallow "beach" area where fish can hide. The male started nest-building within three days and began to harass the other two fish. I supposed that these were also males (or females that had already laid) so asked Jim Hall if he would swap two of his fat females for some of mine. He  brought these on 11th April. The remaining two females were taken from the original tank and one new gravid one was installed in this tank and two in the touch-tank. Over the following few days it was noticed that the new females were treated much less aggressively than the others had been and would make advances toward the male by shimmying at broadside to him. We did not see the males trying to attract females to the nest. 

 A clump of about 30 small white eggs (each about 1 mm diam.) was noticed on 13th April in the "Gelliswick Bay" tank. The male was fanning these with his pectoral fins and had added new materials to the nest. The female was being kept well away from the nest now and was behaving exactly as he other fish had done. Several days later she also sustained damage to the caudal area and was removed. The male continued to defend the nest agains all-comers, including a juvenile Common Cuttle, Sepia vulgaris, of about 100 mm length and much greater bulk than the stickleback.

 The nest in the touch-tank was also guarded assiduously by the male. Other sticklebacks as far away as 1.4 m were harassedand all other fish, including much larger blennies, were kept well away by frenzied ramming attacks.(No evidence of use of the dorsal spines was seen as reported by other writers). 


9 May 2012
I caught a 5lb+ bass in the Menai Straits Anglesey. I would have returned a fish of this size but it had swallowed the bait so decided to eat this one. As I emptied the stomach I found a fish 15 cm long. As I did not know what this fish was I put it in bag and put it in the freezer. On my way home I called in at Anglesey bait centre and they told me it was a stickleback.  

Report by Archie Stubbs  

Information wanted: Please send any records of this fish, with location, date, who discovered it, how it was identified, prevalence, common name and any other details to 
Shorewatch Project EMail 

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